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The online version of The Merck Manual—Second Home
Edition takes advantage of the flexibility of the web to
present updates, changes, and corrections on a regular basis. Thus,
the online version may contain material not yet in print. Details
on updates and new topics appear below.
New and Updated Topics
Rofecoxib, one member of the class of pain and arthritis
drugs known as COX-2 inhibitors (coxibs), appears to increase the
risk of heart attack and stroke after long-term use and has been
withdrawn from the market. The potential for similar adverse effects
with other coxibs is currently being studied. Because one recent
study has shown a 2.5-fold increase in cardiovascular problems with another
member of the class, celecoxib, current FDA recommendations are
to limit use of any coxib to people at high risk of gastrointestinal
bleeding, who have a history of intolerance to other NSAIDs, or
who are not doing well on other NSAIDs. Caution should be taken
with use of coxibs for long periods or by people with risk factors
for heart attack and stroke.
Contributors
Sep 1, 2008
We gratefully acknowledge the expertise of the contributors
to our current online version. The subject(s) that they are responsible
for are listed after their affiliations....
Introduction
Aug 1, 2008
Minerals are necessary
for the normal functioning of the body's cells. The body needs large
quantities of calcium, chloride, magnesium, phosphate, potassium,
and sodium. These minerals are called macrominerals. Bone,
muscle, heart, and brain function...
Calcium
Aug 1, 2008
About 99% of the body's
calcium is stored in the bones, but cells (particularly muscle cells)
and blood also contain calcium. Calcium is essential for the following:Formation of bone and teeth
Muscle contraction
Normal functioning of many enzymes
Blo...
Chromium
Aug 1, 2008
Chromium enables insulin (which
controls blood sugar levels) to function and helps in the processing
(metabolism) and storage of carbohydrates, protein, and fat. Only
a small amount of the chromium in food is absorbed. Chromium is
absorbed better whe...
Copper
Aug 1, 2008
Most of the copper in
the body is located in the liver, bones, and muscle, but traces
of copper occur in all tissues of the body. The liver excretes excess
copper into the bile for elimination from the body. Copper is a
component of many enzymes, inc...
Fluoride
Aug 1, 2008
In the body, most fluoride
is contained in bones and teeth. Fluoride is necessary for the formation
and health of bones and teeth....
Iodine
Aug 1, 2008
The thyroid gland contains
most of the iodine in the body. Iodine in the thyroid gland is necessary
for the formation of thyroid hormones. Iodine occurs in seawater.
A small amount of iodine enters the atmosphere and, through rain,
enters ground wate...
Iron
Aug 1, 2008
Much of the iron in the
body is contained in hemoglobin. Hemoglobin is the
component of red blood cells that enables them to carry oxygen and
deliver it to the body's tissues. Iron also is an important component
of muscle cells. It is also necessary ...
Magnesium
Aug 1, 2008
Bone contains most of
the body's magnesium. Blood contains very little. Magnesium is necessary
for the formation of bone and teeth and for normal nerve and muscle
function. Many enzymes in the body depend on magnesium to function
normally. The body o...
Molybdenum
Aug 1, 2008
Molybdenum is required
for processing (metabolizing) nitrogen, activating certain enzymes,
and enabling cells to function normally. Molybdenum also helps break
down sulfites (which occur in foods naturally and are added as preservatives)....
Phosphate
Aug 1, 2008
In the body, almost all
phosphorus is combined with oxygen, forming phosphate. Bone contains
about 85% of the body's phosphate. The rest is located primarily
inside cells, where it is involved in energy production....
Potassium
Aug 1, 2008
Most of the body's potassium
is located inside the cells. Potassium is necessary for the normal
functioning of cells, nerves, and muscles....
Selenium
Aug 1, 2008
Selenium occurs in all
tissues. Selenium works with vitamin E as an antioxidant. It helps
protect cells against damage by free radicals, which are reactive
by-products of normal cell activity. Selenium may help protect against
some cancers. Selenium ...
Sodium
Aug 1, 2008
Most of the body's sodium
is located in blood and in the fluid around cells. Sodium helps
the body keep fluids in a normal balance (see ).
Sodium plays a key role in normal nerve and muscle function....
Zinc
Aug 1, 2008
Zinc is widely distributed
in the body—in bones, teeth, hair, skin, liver, muscle, white blood
cells, and testes. It is a component of more than 100 enzymes, including
those involved in the formation of RNA (ribonucleic acid) and DNA
(deoxyribonuclei...
Obesity
Aug 1, 2008
Obesity is
the accumulation of excessive body fat.Obesity usually results from
consuming too many calories and not burning enough calories in physical
activity.
Being obese increases the risk of many disorders,
such as diabetes, high blood pressure, ...
Bariatric
Surgery
Aug 1, 2008
Bariatric
surgery alters the stomach, intestine, or both to produce weight
loss....
Metabolic
Syndrome
Aug 1, 2008
Metabolic
syndrome (also called syndrome X or insulin resistance syndrome)
is characterized by excess abdominal fat, resistance to the effects
of insulin (insulin resistance), abnormal levels of fats in the
blood, and high blood pressure.
Excess abdo...
Introduction
Aug 1, 2008
Cholesterol and triglycerides
are important fats (lipids) in the blood. Cholesterol is an essential
component of cell membranes, brain and nerve cells, and bile, which
helps the body absorb fats and fat-soluble vitamins. The body uses
cholesterol to ...
Dyslipidemia
Aug 1, 2008
Dyslipidemia
is abnormal levels of lipids (cholesterol, triglycerides, or both)
carried by lipoproteins in the blood. This term includes hyperlipoproteinemia
(hyperlipidemia), which refers to abnormally high levels of total
cholesterol, low density l...
Hypolipoproteinemia
Aug 1, 2008
Hypolipoproteinemia
is abnormally low levels of lipids in the blood.Low lipid levels may result
from rare genetic abnormalities or other disorders.
People with these genetic abnormalities may have
fatty stools, grow poorly, and be mentally retarded.
...
Introduction
Aug 1, 2008
Water accounts for about
one half to two thirds of an average person's weight. Fat tissue has
a lower percentage of water and women tend to have more fat, so
the percentage of water in the average woman is lower (52 to 55%)
than it is in the average ...
Dehydration
Aug 1, 2008
Dehydration
is a deficiency of water in the body.Vomiting, diarrhea, excessive
sweating, and use of diuretics may cause dehydration.
People feel thirsty, and as dehydration worsens,
they may sweat less and excrete less urine.
If dehydration is severe...
Overhydration
Aug 1, 2008
Overhydration
is an excess of water in the body.
People can have overhydration if they drink too
much or if they have a disorder that decreases the body's ability
to excrete water.
Often, no symptoms occur, but people may become
confused or have seiz...
Introduction
Aug 1, 2008
Porphyrias
are a group of disorders caused by deficiencies of enzymes involved
in the production of heme....
Porphyria
Cutanea Tarda
Aug 1, 2008
Porphyria
cutanea tarda is the most common porphyria and causes blistering
and fragility of skin exposed to sunlight.People have chronically recurring
blisters on the sun-exposed areas of their bodies.
Doctors test urine and stool samples for high le...
Acute
Intermittent Porphyria
Aug 1, 2008
Acute intermittent
porphyria, which causes abdominal pain and neurologic symptoms,
is the most common acute porphyria.
Many people never experience symptoms.
Symptoms may include acute onset of vomiting, abdominal
or back pain, weakness in arms or le...
Erythropoietic
Protoporphyria
Aug 1, 2008
Erythropoietic
protoporphyria is a condition characterized by photosensitivity.The heme precursor protoporphyrin
accumulates in the bone marrow and red blood cells.
People have severe skin pain and swelling soon after
exposure to sunlight.
Doctors te...
Introduction
Aug 1, 2008
A cancer is an abnormal
growth of cells (usually derived from a single cell). The cells have
lost normal control mechanisms and thus are able to expand continuously,
invade adjacent tissues, migrate to distant parts of the body, and
promote the growt...
Development
and Spread
Aug 1, 2008
Cancerous cells develop
from healthy cells in a complex process called malignant transformation....
Risk
Factors for Cancer
Aug 1, 2008
Many genetic and environmental
factors increase the risk of developing cancer. However, not all
people who are exposed to carcinogens or who have other risk factors
develop cancer....
Defenses
Against Cancer
Aug 1, 2008
Even when a cell becomes
cancerous, the immune system is thought to be able to recognize
it as abnormal and destroy it before it replicates or spreads. Cancer
is more likely to progress in people whose immune system is altered
or impaired, as in peop...
Acne
Aug 1, 2008
Acne is a
common skin condition producing pimples on the face and upper torso.Acne is caused by a buildup
of dead skin cells, bacteria, and dried sebum that block the hair
follicles in the skin.
Pimples, cysts, and sometimes abscesses form on
the ski...
Introduction
Aug 1, 2008
Hair originates in the
hair follicles. These follicles are located in the dermis, the skin layer
just below the surface layer and above the subcutaneous fat. Hair
follicles are present everywhere on the surface of the body except the
lips, palms of t...
Hirsutism
and Hypertrichosis
Aug 1, 2008
Hirsutism is
the excessive growth of thick or dark hair in women in locations
that are more typical of male hair patterns (for example, mustache,
beard, central chest, shoulders, lower abdomen, back, and inner
thighs). Hypertrichosis is an increase i...
Alopecia
Aug 1, 2008
Alopecia is
the loss of hair on the head or on any other part of the body.Hair loss may occur because
of changes in hormone levels, the use of certain drugs, stress,
and some skin disorders.
Doctors diagnose the type of hair loss by examining
the hai...
Ingrown
Beard Hairs
Aug 1, 2008
Pseudofolliculitis
barbae (ingrown beard hairs) is inflammation caused by hairs that curl
so that the tips puncture the skin....
Temporomandibular
Disorders
Jul 1, 2008
The temporomandibular
joints are the connections between the temporal bones of the skull
and the lower jawbone (mandible). There are two temporomandibular
joints, one on each side of the face just in front of the ears. Ligaments,
tendons, and muscles...
Introduction
Jul 1, 2008
Nutrition is
the process of consuming, absorbing, and using nutrients needed
by the body for growth, development, and maintenance of life....
Carbohydrates, Proteins,
and Fats
Jul 1, 2008
Carbohydrates, proteins,
and fats supply 90% of the dry weight of the diet and 100% of its
energy. All three provide energy (measured in calories), but the
amount of energy in 1 gram (1/28 ounce)
differs: 4 calories in a gram of carbohydrate or prote...
Vitamins
and Minerals
Jul 1, 2008
Vitamins and minerals are
essential nutrients. That is, they cannot be synthesized by the
body and so must be consumed in the diet....
Fiber
Jul 1, 2008
Some foods contain fiber,
which is a tough complex carbohydrate. Fiber may be partly soluble:
It dissolves in water, and the body may be able to digest some of
it. Or it may be insoluble: It does not dissolve in water, and the body
cannot digest it. ...
Food
Additives and Contaminants
Jul 1, 2008
...
Calories
Jul 1, 2008
A calorie is a measure
of energy. Foods have calories. That is, foods supply the body with energy,
which is released when foods are broken down during digestion. Energy
enables cells to do all of their functions, including building proteins
and other...
Nutritional
Requirements
Jul 1, 2008
General guidelines for
a healthy diet have been developed even though daily nutritional requirements,
including those for essential nutrients, vary, depending on age,
sex, height, weight, physical activity, and the rate at which the
body burns calori...
Diets
Jul 1, 2008
A diet is whatever a person
eats, regardless of the goal—whether it is losing weight, gaining
weight, reducing fat intake, avoiding carbohydrates, or having no
particular goal. However, the term is often used to imply a goal
of losing weight, which i...
Introduction
Jul 1, 2008
An important property
of blood is its degree of acidity or alkalinity. Body acidity increases when
the level of acidic compounds in the body rises (through increased
intake or production, or decreased elimination) or when the level
of basic (alkaline...
Acidosis
Jul 1, 2008
Acidosis is
excessive blood acidity caused by an overabundance of acid in the
blood or a loss of bicarbonate from the blood (metabolic acidosis),
or by a buildup of carbon dioxide in the blood that results from
poor lung function or slow breathing (r...
Alkalosis
Jul 1, 2008
Alkalosis
is excessive blood alkalinity caused by an overabundance of bicarbonate
in the blood or a loss of acid from the blood (metabolic alkalosis),
or by a low level of carbon dioxide in the blood that results from
rapid or deep breathing (respira...
Introduction
Jul 1, 2008
Plasma cell disorders
(plasma cell dyscrasias) are uncommon. They begin when a single group
(clone) of plasma cells multiplies excessively and produces a large
quantity of a single type of antibody (immunoglobulin). Plasma cells
develop from B lympho...
Monoclonal Gammopathies
of Undetermined Significance
Jul 1, 2008
A monoclonal
gammopathy of undetermined significance is a buildup of monoclonal
antibodies produced by abnormal but noncancerous plasma cells....
Multiple
Myeloma
Jul 1, 2008
Multiple myeloma
is a cancer of plasma cells in which abnormal plasma cells multiply
uncontrollably in the bone marrow and occasionally in other parts
of the body.People
often have bone pain and fractures, and they may also have kidney
problems, immu...
Macroglobulinemia
Jul 1, 2008
Macroglobulinemia
(Waldenström's macroglobulinemia) is a plasma cell cancer in which a
single clone of plasma cells produces excessive amounts of a certain
type of large antibody (IgM) called macroglobulins.Although many people have
no symptoms, some...
Heavy
Chain Diseases
Jul 1, 2008
Heavy chain
diseases are plasma cell cancers in which a clone of plasma cells
produces a large quantity of pieces of abnormal antibodies called
heavy chains....
Introduction
Jul 1, 2008
Lymphomas
are cancers of lymphocytes, which reside in the lymphatic system
and in blood-forming organs....
Hodgkin
Lymphoma
Jul 1, 2008
Hodgkin lymphoma
is a type of lymphoma distinguished by the presence of a particular kind
of cancer cell called a Reed-Sternberg cell.The cause is unknown.
Lymph nodes enlarge but are not painful.
Other symptoms, such as muscle weakness, fever,
and s...
Non-Hodgkin
Lymphomas
Jul 1, 2008
Non-Hodgkin
lymphomas are a diverse group of cancers that develop in B or T
lymphocytes.Often,
lymph nodes in the neck, under the arms, or in the groin enlarge
rapidly and painlessly.
People may have pain or shortness of breath or other
symptoms when...
Introduction
Jul 1, 2008
In myeloproliferative
disorders (myelo = bone marrow, proliferative = rapid multiplication),
the blood-producing cells in the bone marrow (precursor cells) develop
and reproduce excessively or are crowded out by an overgrowth of
fibrous tissue. Typic...
Polycythemia
Vera
Jul 1, 2008
Polycythemia
vera (primary polycythemia) is a disorder of the blood-producing
cells of the bone marrow that results in overproduction of red blood
cells.The cause
is not known.
People may feel tired and weak, light-headed, or
short of breath.
Blood t...
Myelofibrosis
Jul 1, 2008
Myelofibrosis
is a disorder in which fibrous tissue replaces the blood-producing
cells in the bone marrow, resulting in abnormally shaped red blood
cells, anemia, and an enlarged spleen.Myelofibrosis may occur on
its own or as a result of other blood...
Thrombocythemia
Jul 1, 2008
Thrombocythemia
(primary thrombocythemia) is a disorder in which excess platelets
are produced, leading to abnormal blood clotting or bleeding.The cause is not known.
The hands and feet may tingle, and the fingertips
may feel cold.
Routine blood test...
Introduction
Jul 1, 2008
Immunization enables the
body to better defend itself against diseases caused by certain bacteria
or viruses. Immunization may occur on its own (when people are exposed
to bacteria or viruses), or doctors may provide it. When people
are immunized aga...
Common Vaccinations
Jul 1, 2008
Children typically are
given a number of vaccines according to a standard schedule (see ). If vaccines are
missed, most can be given later, according to a catch-up schedule.
Adults may also be advised to receive certain vaccines. When advising
adults...
Vaccination
Before Foreign Travel
Jul 1, 2008
Residents of the United
States may be required to receive specific vaccines before traveling
to areas that have infectious diseases not normally found in the
United States (see ).
Recommendations change frequently in response to disease outbreaks.
Th...
Introduction
Jul 1, 2008
The outer ear consists
of the external part of the ear (pinna or auricle) and the ear canal (external
auditory meatus—see ).
Disorders of the outer ear include blockages, infections (external
otitis and perichondritis), eczema, and tumors. The outer ...
Blockages
Jul 1, 2008
Earwax (cerumen) may block
the ear canal. Even large amounts of earwax often cause no symptoms.
Symptoms can range from itching to a loss of hearing. A doctor may
remove the earwax by gently flushing out the ear canal with warm
water (irrigation).
Ho...
External
Otitis
Jul 1, 2008
External otitis
is infection of the ear canal.
External otitis is caused by bacteria or, rarely,
fungi.
Typical symptoms are itching, pain, and discharge.
A doctor looks in the ear with an otoscope (a device
for viewing the canal and eardrum) for red...
Perichondritis
Jul 1, 2008
Perichondritis
is infection of the tissue surrounding the cartilage of the earlobe
(pinna), ear canal, or both....
Tumors
Jul 1, 2008
Tumors of the ear may
be noncancerous (benign) or cancerous (malignant). Most ear tumors
are found when people see them or when a doctor looks in the ear
because people notice their hearing seems decreased....
Injury
Jul 1, 2008
A number of different
injuries can affect the outer ear. A blunt blow to the external
ear can cause bruising between the cartilage and the layer of connective
tissue around it (perichondrium). When blood collects in this area,
the external ear become...
Introduction
Jul 1, 2008
The upper part of the
nose consists mostly of bone. The lower part of the nose gains its support
from cartilage. Inside the nose is a hollow cavity (nasal cavity),
which is divided into two passages by a thin sheet of cartilage
and bone called the na...
Fractures
of the Nose
Jul 1, 2008
Typically, a broken nose bleeds, hurts, and swells.
To diagnose a broken nose, a doctor looks at and
feels the bridge of the nose.
Doctors sometimes need to push the broken pieces
of bone back into place....
Deviated
Septum
Jul 1, 2008
Usually, the nasal septum
is straight, lying about in the middle of the two nostrils. Occasionally,
it may be bent (deviated) because of a birth defect or injury and
positioned so that one nostril is much smaller than the other. Most
people have some...
Perforations
of the Septum
Jul 1, 2008
Ulcers and holes (perforations)
in the nasal septum may occur as a result of nasal surgery; repeated
injury such as that resulting from picking the nose; cosmetic piercing;
exposure to toxins (such as acids, chromium, phosphorus, and copper
vapor); c...
Nosebleeds
Jul 1, 2008
Nose picking and injuries are the most common causes
of nosebleeds.
People typically bleed from the front part of the
nose.
Avoiding nose picking, humidifying the air during
the winter, and, for some people, moistening the front of the nasal
septum ...
Nasal
Vestibulitis
Jul 1, 2008
Nasal vestibulitis
is infection of the area just inside the opening of each nostril
(the nasal vestibule)....
Rhinitis
Jul 1, 2008
Rhinitis is
inflammation and swelling of the mucous membrane of the nose, characterized by
a runny nose and stuffiness and usually caused by the common cold
(see )
or an allergy (see ).
Colds and allergies are the most common causes of
rhinitis.
Symp...
Nasal
Polyps
Jul 1, 2008
Nasal polyps
are fleshy outgrowths of the mucous membrane of the nose.Nasal polyps are more likely
to develop in people who have allergies or asthma.
Some of the symptoms caused by polyps are nasal
obstruction and congestion.
Doctors usually diagnose...
Sinusitis
Jul 1, 2008
Sinusitis
is inflammation of the sinuses, most commonly caused by a viral
or bacterial infection or by an allergy.Some of the most common symptoms
of sinusitis are pain, tenderness, nasal congestion, and headache.
The diagnosis is based on symptoms, ...
Introduction
Jul 1, 2008
Disorders of the throat
(pharynx) and voice box (larynx) may represent short-lived (acute) inflammation
and infections, persistent (chronic) inflammation, or abnormal growths. Specific
disorders include vocal cord polyps and nodules, contact ulcers,
...
Tonsillar
Cellulitis and Abscess
Jul 1, 2008
Tonsillar
cellulitis is a bacterial infection of the tissues around
the tonsils. A tonsillar abscess is a collection of
pus behind the tonsils.Sometimes,
bacteria that infect the throat spread deep into surrounding tissues.
Typical symptoms include s...
Epiglottitis
Jul 1, 2008
Epiglottitis
is a bacterial infection of the epiglottis.Epiglottitis may block the
windpipe (trachea) and be fatal
The main symptoms are severe sore throat and noisy,
difficult breathing.
Doctors make the diagnosis by looking at the epiglottis
in the...
Laryngitis
Jul 1, 2008
Laryngitis
is inflammation of the voice box (larynx).A virus is usually what causes
the inflammation.
Typical symptoms include hoarseness and loss of
voice.
The diagnosis is based on symptoms and changes of
the voice.
Usually, resting the voice and a...
Vocal
Cord Nodules and Polyps
Jul 1, 2008
Vocal cord
nodules and polyps are noncancerous (benign) growths that cause
hoarseness and a breathy voice....
Vocal
Cord Contact Ulcers
Jul 1, 2008
Contact ulcers
are raw sores on the mucous membrane covering the cartilage to which
the vocal cords are attached....
Vocal
Cord Paralysis
Jul 1, 2008
Vocal cord
paralysis is the inability to move the muscles that control the
vocal cords.Paralysis
can be caused by tumors, injuries, or nerve damage caused by infection
or toxins.
Typical symptoms include voice changes and possible
difficulty breathin...
Laryngoceles
Jul 1, 2008
Laryngoceles
are outpouchings of the mucous membrane of a part of the voice box
(larynx)....
Introduction
Jul 1, 2008
Often, cancers of the
nose and throat are considered together by doctors because of certain
similarities. Among the similarities are the causes. Most people
who have cancers of the nose and throat use tobacco, drink alcohol, or
both....
Laryngeal
Cancer
Jul 1, 2008
Cancer of the voice box
(larynx), a common area of cancer within the head and neck, occurs
more often in men than in women. It is linked to cigarette smoking
and alcohol consumption....
Paranasal
Sinus Cancer
Jul 1, 2008
Cancer of the paranasal
sinuses occurs mainly in the maxillary and ethmoid sinuses (see ). Although rare
in the United States, these cancers are more common in Japan and
among the Bantu people of South Africa. Doctors are not sure what
causes these c...
Nasopharyngeal
Cancer
Jul 1, 2008
Cancer of the nasal passages
and upper throat (nasopharynx) may occur in people of any age group.
Although rare in North America, cancer of the nasopharynx is one
of the most common cancers in Asia. This cancer is also more common
among Chinese peopl...
Tonsillar
Cancer
Jul 1, 2008
Cancer of the tonsils
occurs predominantly in men. It is strongly linked to smoking and alcohol
consumption. Recent evidence suggests that human papillomavirus
(HPV) is associated with tonsil cancer as well. People who have
HPV-related tumors and who...
Cataract
Jul 1, 2008
A cataract
is a clouding (opacity) of the lens of the eye that causes a progressive,
painless loss of vision.Vision
may be blurred, contrast may be lost, and halos may be visible around
lights.
Doctors can recognize cataracts by looking at the eye
wi...
Uveitis
Jul 1, 2008
Uveitis is
inflammation anywhere in the pigmented inside lining of the eye,
known as the uvea, or uveal tract.
The uvea may become inflamed because of infection,
a bodywide autoimmune disorder (which causes the body to attack
its own tissues), or for...
Introduction
Jul 1, 2008
The small photoreceptors
of the retina (the inner surface at the back of the eye) sense light and
transmit impulses to the optic nerve.
The optic nerve from each eye carries impulses to the brain, where
visual information is interpreted. Damage to an...
Papilledema
Jul 1, 2008
Papilledema
is a condition in which increased pressure in or around the brain
causes the optic nerve to swell where it enters the eye.Symptoms may be fleeting disturbances
in vision, headache, vomiting, or a combination.
Doctors make the diagnosis by...
Optic
Neuritis
Jul 1, 2008
Optic neuritis
is inflammation of the optic nerve anywhere along its course.Multiples sclerosis is the
most common cause.
Loss of vision may develop, and moving the eye may
hurt.
Magnetic resonance imaging (MRI) is done.
If multiple sclerosis seems p...
Ischemic Optic
Neuropathy
Jul 1, 2008
Ischemic optic
neuropathy is damage of the optic nerve caused by a blockage of
its blood supply.Blockage
can occur with or without inflammation of the arteries (typically
in association with a disorder called temporal arteritis)
Vision may suddenly d...
Toxic
Amblyopia (Nutritional Amblyopia)
Jul 1, 2008
Toxic amblyopia
(nutritional amblyopia) is damage to the optic nerve caused by undernutrition
or by exposure to a substance that is harmful to the optic nerve,
such as lead, wood alcohol, antifreeze, or certain drugs.A nutritional deficiency or
toxic...
Introduction
Jun 1, 2008
Somatoform
disorders include several mental health disorders. In some, people
report physical symptoms or concerns that suggest but are not fully
explained by a physical disorder. In one, people are preoccupied
with a slight or nonexistent defect in ...
Body
Dysmorphic Disorder
Jun 1, 2008
In body dysmorphic
disorder, a preoccupation with a nonexistent or slight defect in
appearance results in significant distress or impairs functioning.People typically spend hours
a day worrying about their perceived defect, which may involve any
body...
Conversion
Disorder
Jun 1, 2008
In conversion
disorder, physical symptoms that resemble those of a neurologic
disorder develop. The symptoms are triggered by mental factors such
as conflicts or other stresses.
An arm or leg may be paralyzed, or people may lose
their sense of touch,...
Hypochondriasis
Jun 1, 2008
In hypochondriasis,
people are preoccupied with the fear of having a serious disease
or are preoccupied with the belief that they actually have a disease.
These feelings are usually based on a misinterpretation of normal
bodily sensations or minor ph...
Somatization
Disorder
Jun 1, 2008
Somatization
disorder is a chronic, severe disorder characterized by many recurring
physical symptoms that cannot be fully explained by a physical disorder.
These symptoms include some combination of pain and digestive, sexual,
and neurologic symptom...
Introduction
Jun 1, 2008
Mood disorders
are mental health disorders involving emotional disturbances consisting
of long periods of excessive sadness (depression) or excessive joyousness
or elation (mania). Depression and mania represent the two extremes,
or poles, of mood di...
Depression
Jun 1, 2008
The disorder
depression is a feeling of sadness intense enough to interfere with
functioning. It may follow a recent loss or other sad event but is
out of proportion to that event and lasts beyond an appropriate
length of time.Heredity,
side effects ...
Bipolar Disorder (Manic-Depressive Illness)
Jun 1, 2008
In bipolar
disorder (formerly called manic-depressive illness), episodes of
depression alternate with episodes of mania or a less severe form
of mania called hypomania. Mania is characterized by excessive physical
activity and feelings of elation tha...
Cyclothymic
Disorder
Jun 1, 2008
In cyclothymic
disorder, relatively mild and short episodes of elation (hypomania)
alternate with mild and short episodes of sadness (depression)....
Introduction
Jun 1, 2008
Eating disorders are grouped
into three categories:Anorexia
nervosa: Refusing to maintain a minimally normal body weight,
with or without bingeing and purging
Bulimia nervosa: Bingeing and purging
without weight loss
Binge eating disorder: Bingeing w...
Anorexia
Nervosa
Jun 1, 2008
Anorexia nervosa
is characterized by a relentless pursuit of thinness, a distorted
body image, an extreme fear of obesity, refusal to maintain a minimally
normal body weight, and, in women, the absence of menstrual periods.Anorexia nervosa usually be...
Bulimia
Nervosa
Jun 1, 2008
Bulimia nervosa
is characterized by the repeated rapid consumption of large amounts
of food (bingeing), followed by attempts to rid the body of the
excess food consumed (purging).
People eat large amounts of food, then induce vomiting,
use laxatives,...
Binge
Eating Disorder
Jun 1, 2008
Binge eating
disorder is characterized by the consumption of large amounts of
food with a feeling of loss of control (bingeing). Bingeing is not
followed by attempts to rid the body of the excess food consumed
(purging).Binge
eating disorder is more ...
Introduction
Jun 1, 2008
Occasionally everyone
has minor problems integrating their memories, perceptions, identity,
and consciousness. For example, people may drive somewhere and then
realize that they do not remember the drive. They may not remember
it because they are abs...
Depersonalization
Disorder
Jun 1, 2008
Depersonalization
disorder involves a persistent or recurring feeling of being detached from
one's body or mental processes (depersonalization) and a feeling
of being an outside observer of one's life.The disorder is usually triggered
by life-threate...
Dissociative
Amnesia
Jun 1, 2008
Dissociative
amnesia is amnesia caused by trauma or stress, resulting in an inability
to recall important personal information.People have gaps in their
memory, which may span a few minutes to years.
After tests are done to rule out other possible
ca...
Dissociative
Fugue
Jun 1, 2008
Dissociative
fugue involves one or more episodes of sudden, unexpected, but purposeful travel
from home during which people cannot remember some or all of their
past life, including who they are (their identity). These episodes
are called fugues.Unbe...
Dissociative
Identity Disorder
Jun 1, 2008
In dissociative
identity disorder, formerly called multiple personality disorder,
two or more identities alternate within the same person.Extreme stress during childhood
may prevent some children from integrating their experiences into
one cohesive i...
Introduction
Jun 1, 2008
Schizophrenia and delusional
disorder are distinct disorders that may share certain features,
such as paranoia, suspiciousness, and unrealistic thinking. However,
schizophrenia is associated with psychosis—a loss of contact with
reality—and with a de...
Schizophrenia
Jun 1, 2008
Schizophrenia
is a mental disorder characterized by loss of contact with reality
(psychosis), hallucinations (usually, hearing voices), firmly held
false beliefs (delusions), abnormal thinking, a restricted range
of emotions (flattened affect), dimin...
Delusional
Disorder
Jun 1, 2008
Delusional
disorder is characterized by one or more false beliefs that persist
for at least 1 month.The
false beliefs tend to be ordinary things that could occur, such
as being deceived by a spouse.
This disorder may develop in people with a paranoid...
Diabetes
Mellitus
Jun 1, 2008
Diabetes mellitus
is a disorder in which blood sugar (glucose) levels are abnormally
high because the body does not produce enough insulin to meet its
needs.Urination
and thirst are increased, and people lose weight when they are not
trying to.
Diabe...
Multiple
Endocrine Neoplasia Syndromes
Jun 1, 2008
Multiple endocrine
neoplasia syndromes are rare, inherited conditions in which several
endocrine glands develop noncancerous (benign) or cancerous (malignant)
tumors or grow excessively without forming tumors.Multiple endocrine neoplasia
syndromes ar...
Introduction
Jun 1, 2008
Anemia is a
condition in which the number of red blood cells or the amount of
hemoglobin (the protein that carries oxygen in them) is low....
Anemia
Due to Excessive Bleeding
Jun 1, 2008
Anemia from
excessive bleeding results when loss of red blood cells through
bleeding exceeds production of new red blood cells.When blood loss is rapid,
blood pressure falls, and people may be dizzy.
When blood loss occurs gradually, people may be
ti...
Iron
Deficiency Anemia
Jun 1, 2008
Iron deficiency
anemia results from low or depleted stores of iron, which is needed
to produce red blood cells.
Excessive bleeding is the most common cause.
People may be weak, short of breath, and pale.
Blood tests can detect low levels of iron.
Iro...
Vitamin
Deficiency Anemia
Jun 1, 2008
Vitamin deficiency
anemia results from low or depleted levels of vitamin B12 or
folate (folic acid).People
may be weak, short of breath, and pale.
Nerves may also malfunction.
Blood tests can detect abnormal cells that indicate
vitamin deficiency ane...
Anemia
of Chronic Disease
Jun 1, 2008
In anemia
of chronic disease, some chronic disorder slows the production of
red blood cells, the result of production of proteins called cytokines
that interfere with the production of red blood cells....
Autoimmune
Hemolytic Anemia
Jun 1, 2008
Autoimmune
hemolytic anemia is a group of disorders characterized by a malfunction
of the immune system that produces autoantibodies, which attack
red blood cells as if they were substances foreign to the body.Some people have no symptoms,
and other ...
Sickle
Cell Disease
Jun 1, 2008
Sickle cell
disease is an inherited condition characterized by sickle (crescent)-shaped
red blood cells and chronic anemia caused by excessive destruction
of red blood cells.People
usually have anemia and jaundice.
Worsening anemia, fever, and shortn...
Hemoglobin C, S-C, and
E Diseases
Jun 1, 2008
Hemoglobin
C, S-C, and E diseases are inherited conditions characterized by
abnormally shaped red blood cells and chronic anemia that is caused
by excessive destruction of red blood cells....
Thalassemias
Jun 1, 2008
Thalassemias
are a group of inherited disorders resulting from an imbalance in
the production of one of the four chains of amino acids that make
up hemoglobin (the oxygen-carrying protein found in red blood cells).Symptoms depend on the type
of thala...
Introduction
Jun 1, 2008
White
blood cells (leukocytes) are an important part of the body's defense
against infectious organisms and foreign substances. To defend the
body adequately, a sufficient number of white blood cells must receive
a message that an infectious organism...
Neutropenia
Jun 1, 2008
Neutropenia
is an abnormally low number of neutrophils in the blood.Neutropenia significantly
increases the risk of life-threatening infection.
Neutropenia is often caused by cancer chemotherapy
or radiation therapy.
Doctors suspect neutropenia in pe...
Neutrophilic
Leukocytosis
Jun 1, 2008
Neutrophilic
leukocytosis is an abnormally high number of neutrophils in the
blood....
Lymphocytopenia
Jun 1, 2008
Lymphocytopenia
is an abnormally low number of lymphocytes in the blood.Many disorders can decrease
the number of lymphocytes in the blood, but AIDS and malnutrition
are the most common.
People may have no symptoms, or they may have fever
and other s...
Lymphocytic
Leukocytosis
Jun 1, 2008
Lymphocytic
leukocytosis is an abnormally high number of lymphocytes in the
blood....
Monocyte
Disorders
Jun 1, 2008
Monocytes help other white
blood cells remove dead or damaged tissues, destroy cancer cells,
and regulate immunity against foreign substances. Monocytes are
produced in the bone marrow and then enter the bloodstream, where
they account for about 1 to...
Eosinophilic
Disorders
Jun 1, 2008
Eosinophils usually account
for less than 7% of the circulating leukocytes (100 to 500 eosinophils
per microliter of blood). These cells have a role in the protective
immunity against certain parasites but also contribute to the inflammation
that occ...
Basophilic
Disorders
Jun 1, 2008
Basophils account for
less than 3% of the circulating leukocytes (0 to 300 basophils per microliter
of blood). These cells have some role in immune surveillance and
wound repair. Basophils can release histamine and other mediators
and play a role in ...
Introduction
Jun 1, 2008
Leukemias
are cancers of white blood cells or of cells that develop into white
blood cells....
Acute
Lymphocytic Leukemia (ALL)
Jun 1, 2008
Acute lymphocytic
(lymphoblastic) leukemia is a life-threatening disease in which
the cells that normally develop into lymphocytes become cancerous
and rapidly replace normal cells in the bone marrow.People may have symptoms,
such as fever, weakness,...
Acute
Myelocytic Leukemia (AML)
Jun 1, 2008
Acute myelocytic
(myeloid, myelogenous, myeloblastic, myelomonocytic) leukemia is
a life-threatening disease in which the cells that normally develop
into neutrophils, basophils, eosinophils, and monocytes become cancerous and
rapidly replace normal ...
Chronic
Lymphocytic Leukemia (CLL)
Jun 1, 2008
Chronic lymphocytic
leukemia is a disease in which mature lymphocytes become cancerous and
gradually replace normal cells in lymph nodes.People may have no symptoms
or they may have general symptoms such as tiredness.
People may also have enlarged ly...
Chronic
Myelocytic Leukemia (CML)
Jun 1, 2008
Chronic myelocytic
(myeloid, myelogenous, granulocytic) leukemia is a disease in which cells
that normally would develop into neutrophils, basophils, eosinophils,
and monocytes become cancerous.
People pass through a phase in which they have nonspeci...
Introduction
Jun 1, 2008
The spleen, a spongy, soft
organ about as big as a person's fist, is located in the upper left part
of the abdomen, just under the rib cage. The splenic artery brings
blood to the spleen from the heart. Blood leaves the spleen through
the splenic vei...
Enlarged
Spleen
Jun 1, 2008
Many disorders, including infections, anemias, and
cancers, can cause an enlarged spleen.
Symptoms are usually not very specific but can include
fullness or pain in the upper left abdomen or back.
Usually doctors can feel an enlarged spleen, but x-r...
Spleen
Injury
Jun 1, 2008
An injured spleen is usually painful.
Imaging tests such as ultrasonography or computed
tomography are used to diagnose an injured spleen.
Blood transfusions are often needed to treat a spleen
injury, and sometimes surgery to remove or repair the sp...
Introduction
Jun 1, 2008
The conjunctiva
is the thin, transparent lining that covers the back of the eyelid
and loops back to cover the sclera (the white of the eye), right
up to the edge of the cornea (see ). The conjunctiva helps protect
the eye by keeping small foreign ob...
Infectious Conjunctivitis
Jun 1, 2008
Infectious
conjunctivitis is inflammation of the conjunctiva usually caused
by viruses or bacteria.Bacteria
and viruses can infect the conjunctiva.
Redness, irritation, tearing or discharge, and sensitivity
to light are common.
Good hygiene helps pre...
Trachoma
Jun 1, 2008
Trachoma (granular
conjunctivitis, Egyptian ophthalmia) is a prolonged infection of
the conjunctiva caused by the higher bacterium Chlamydia
trachomatis.
Chlamydia trachomatis can
infect the eye, usually in children who live in lesser-developed,
hot,...
Allergic
Conjunctivitis
Jun 1, 2008
Allergic conjunctivitis
is inflammation of the conjunctiva caused by an allergic reaction.Allergic reactions may inflame
the conjunctiva.
Redness, irritation, swelling, and discharge are
common.
Various eye drops may help decrease inflammation....
Episcleritis
Jun 1, 2008
Episcleritis
is inflammation of the tissue lying between the sclera and the conjunctiva....
Scleritis
Jun 1, 2008
Scleritis
is a deep, extremely painful inflammation and purple discoloration
of the sclera (the white of the eye) that may severely damage vision....
Noncancerous
Growths
Jun 1, 2008
Two kinds of noncancerous
(benign) growths commonly develop on the conjunctiva—pinguecula
and pterygium. They both are more common among older people and probably
occur as a result of long-term ultraviolet radiation exposure. Doctors
easily recognize...
Introduction
May 1, 2008
The brain and spinal cord
are remarkably resistant to infection, but when they become infected,
the consequences are often very serious. Infections may be caused
by bacteria, viruses, fungi, or, occasionally, protozoa or parasites.
Another group of b...
Acute
Bacterial Meningitis
May 1, 2008
Acute bacterial
meningitis is rapidly developing inflammation of the subarachnoid
space (located within the layers of tissue covering the brain and
spinal cord) that is caused by bacteria.Older children and adults
develop a stiff neck, usually with a...
Chronic
Meningitis
May 1, 2008
Chronic meningitis
is a slowly developing inflammation of the subarachnoid space (located
within the layers of tissues covering the brain and spinal cord)
that lasts a month or longer.
People may have a fever, a stiff neck, a headache,
double vision,...
Aseptic
Meningitis
May 1, 2008
Aseptic meningitis
is inflammation of the subarachnoid space (located within the tissues the
layers of covering the brain and spinal cord) that is diagnosed
when standard testing does not detect bacteria.Viruses, often those frequently
present in the...
Rabies
May 1, 2008
Rabies is
a viral infection of the brain that is transmitted by animals and
that causes inflammation of the brain and spinal cord. Once the
virus reaches the spinal cord and brain, rabies is fatal.The virus can be transmitted
when people are bitten b...
Encephalitis
May 1, 2008
Encephalitis
is inflammation of the brain that occurs when a virus directly infects
the brain or when a virus or something else triggers inflammation.
The spinal cord may also be involved, resulting in a disorder called encephalomyelitis.People may h...
Lymphocytic
Choriomeningitis
May 1, 2008
Lymphocytic
choriomeningitis is a flu-like disorder caused by an arenavirus
and often followed by meningitis. It occurs when the tissues covering
the brain and spinal cord become inflamed.Rodents can transmit the virus
to people through contaminated ...
Progressive
Multifocal Leukoencephalopathy
May 1, 2008
Progressive
multifocal leukoencephalopathy is a rare infection of the brain
that is caused by the JC virus.
People with a weakened immune system are most likely
to get the disorder.
People may become clumsy, have trouble speaking,
and become partiall...
Abscess
of the Brain
May 1, 2008
A brain abscess
is a localized collection of pus in the brain.An abscess may form in the
brain when bacteria from an infection elsewhere in the head or in
the bloodstream or from a wound enter the brain.
Headache, sleepiness, nausea, weakness on one ...
Subdural
Empyema
May 1, 2008
A subdural
empyema is a collection of pus that develops under the top layer
of tissue (dura mater) covering the brain, rather than in the brain
itself....
Parasitic
Infections
May 1, 2008
In some parts of the
world, brain infections may be due to worms or other parasites.
These infections are more common in developing countries and rural
areas. They are less common in the United States....
Suicidal
Behavior
May 1, 2008
Suicidal behavior
includes three types of self-destructive acts: completed suicide,
attempted suicide, and suicide gestures. Thoughts and plans about
suicide are called suicide ideation.
Suicide usually results from the interaction of many
factors, u...
Introduction
May 1, 2008
The thyroid
is a small gland, measuring about 2 inches (5 centimeters) across,
that lies just under the skin below the Adam's apple in the neck.
The two halves (lobes) of the gland are connected in the middle
(called the isthmus), giving the thyroid ...
Hyperthyroidism
May 1, 2008
Hyperthyroidism
is overactivity of the thyroid gland that leads to high levels of
thyroid hormones and speeding up of vital body functions.Graves' disease is the most
common cause of hyperthyroidism.
Heart rate and blood pressure may increase, heart
...
Hypothyroidism
May 1, 2008
Hypothyroidism
is underactivity of the thyroid gland that leads to inadequate production of
thyroid hormones and a slowing of vital body functions.Facial expressions become
dull, the voice is hoarse, speech is slow, eyelids droop, and the eyes
and fa...
Hashimoto's
Thyroiditis
May 1, 2008
Hashimoto's
thyroiditis (autoimmune thyroiditis) is chronic, autoimmune inflammation
of the thyroid.Hashimoto's
thyroiditis results when the body attacks the cells of the thyroid
gland—an autoimmune reaction.
Usually, people feel tired and cannot tol...
Subacute
Thyroiditis
May 1, 2008
Subacute
thyroiditis (granulomatous thyroiditis) is acute inflammation of
the thyroid, probably caused by a virus....
Silent
Lymphocytic Thyroiditis
May 1, 2008
Silent lymphocytic
thyroiditis (postpartum thyroiditis) is painless, autoimmune inflammation
of the thyroid that typically develops after childbirth and goes
away on its own....
Cancer
May 1, 2008
The cause of thyroid cancer
is not known, but the thyroid gland is very sensitive to radiation.
Thyroid cancer is more common among people who were treated with
radiation to the head, neck, or chest, most often for noncancerous
(benign) conditions, w...
Carcinoid
Tumors
May 1, 2008
Carcinoid
tumors are noncancerous (benign) or cancerous (malignant) growths
that sometimes produce excessive amounts of hormonelike substances,
resulting in the carcinoid syndrome.
People with carcinoid tumors may have cramping pain
and changes in bo...
Acute Bronchitis
Apr 1, 2008
Bronchitis
is inflammation of the large airways that branch off the trachea
(bronchi), usually caused by infection but sometimes caused by irritation
from inhaling gases, smoke, dust particles, or some types of pollution.Acute bronchitis is usually
c...
Introduction
Apr 1, 2008
Pneumonia
is an infection of the small air sacs of the lungs (alveoli) and
the tissues around them....
Community-Acquired
Pneumonia
Apr 1, 2008
Community-acquired
pneumonia develops in people with limited or no contact with medical
institutions or settings....
Hospital-Acquired
and Institution-Acquired Pneumonia
Apr 1, 2008
Hospital-acquired
pneumonia develops in people who have been hospitalized,
typically after about 2 days or more of hospitalization. Institution-acquired
pneumonia develops in people who reside in nursing homes
or who have contact with medical setting...
Pneumonia
in Immunocompromised People
Apr 1, 2008
Pneumonia
in people whose immune system is weakened (for example, by AIDS,
organ transplantation, or the use of certain drugs) is usually caused
by different organisms than those that cause pneumonia in healthy
people.Pneumocystis
jiroveci pneumonia ...
Aspiration
Pneumonia
Apr 1, 2008
Aspiration
pneumonia is lung infection caused by inhaling mouth secretions,
stomach contents, or both. Chemical pneumonitis is
lung irritation caused by inhalation of substances toxic to the
lungs.Symptoms
include cough and shortness of breath.
Docto...
Asthma
Apr 1, 2008
Asthma is
a condition in which the airways narrow—usually reversibly—in response
to certain stimuli....
Introduction
Apr 1, 2008
Environmental lung diseases
are caused by harmful particles, mists, vapors, or gases that are
inhaled, usually while people work. If the lung disease is due to
inhaled particles, the term pneumoconiosis is often
used. Where within the airways or lung...
Asbestosis
Apr 1, 2008
Asbestosis
is widespread scarring of lung tissue caused by breathing asbestos
dust....
Beryllium
Disease
Apr 1, 2008
Beryllium
disease (sometimes called berylliosis) is a lung inflammation caused
by inhaling dust or fumes that contain beryllium....
Building-Related
Illnesses
Apr 1, 2008
Building-related
illnesses are disorders that affect the lungs as well as other parts
of the body and are caused by exposure to substances within modern
airtight buildings....
Byssinosis
Apr 1, 2008
Byssinosis
is a narrowing of the airways caused by inhaling cotton, flax, or
hemp particles....
Coal
Workers' Pneumoconiosis
Apr 1, 2008
Coal workers'
pneumoconiosis (black lung) is a lung disease caused by deposits
of coal dust in the lungs....
Gas
and Chemical Exposure
Apr 1, 2008
Symptoms depend on which gas or chemical is inhaled
and how deeply and for how long it was inhaled.
Symptoms may include irritation of the eyes or nose,
cough, blood in the sputum, and shortness of breath.
Chest x-rays, computed tomography, and brea...
Occupational
Asthma
Apr 1, 2008
Occupational
asthma is a reversible narrowing of the airways caused by inhaling
work-related particles or vapors that act as irritants or cause
an allergic reaction....
Silicosis
Apr 1, 2008
Silicosis
is permanent scarring of the lungs caused by inhaling silica (quartz)
dust....
Introduction
Apr 1, 2008
Bone tumors
are growths of abnormal cells in bones.Bone tumors may be cancerous
(malignant) or noncancerous (benign) and may develop within the
bone or spread to the bone.
Tumors may cause unexplained, progressively worsening
bone pain, swelling, or ...
Other Bone Abnormalities
Apr 1, 2008
Many noncancerous (benign)
bone abnormalities may resemble bone tumors but are not....
Joint
Tumors
Apr 1, 2008
Tumors rarely affect
joints unless the joints are near a bone or soft-tissue tumor. However, two
conditions—synovial chondromatosis and pigmented villonodular synovitis—occur
in the lining (synovium) of joints. These tumors are noncancerous
(benign) ...
Introduction
Apr 1, 2008
Vasculitic
disorders are characterized by inflammation of the blood vessels
(vasculitis).Usually,
what triggers vasculitis is unknown, but sometimes certain viruses or
drugs trigger it.
People may have general symptoms, such as fever
or fatigue, foll...
Polyarteritis
Nodosa
Apr 1, 2008
Polyarteritis
nodosa is inflammation of medium-sized arteries that damages the
arteries and impairs blood flow through them.Any organ (except the lungs)
can be affected.
Polyarteritis nodosa can be rapidly fatal or develop
gradually.
Symptoms vary de...
Giant
Cell Arteritis
Apr 1, 2008
Giant cell
(temporal) arteritis is chronic inflammation of large arteries of
the head, neck, and upper body. Typically affected are the temporal
arteries, which run through the temples and provide blood to part
of the scalp, the jaw muscles, and sali...
Wegener's
Granulomatosis
Apr 1, 2008
Wegener's
granulomatosis often begins with inflammation of small and medium-sized blood
vessels and tissues in the nose, sinuses, throat, or lungs. It may
progress to inflammation of blood vessels throughout the body (generalized
vasculitis).The
caus...
Behçet's
Syndrome
Apr 1, 2008
Behçet's syndrome
is chronic inflammation that can cause painful mouth sores, skin
blisters, genital sores, and swollen joints. The eyes, blood vessels,
nervous system, and digestive tract may also become inflamed.Typically, sores appear, disappear,
...
Takayasu's
Arteritis
Apr 1, 2008
Takayasu's
arteritis causes chronic inflammation, mainly of the aorta (the
artery that connects directly with the heart), the arteries that branch
off from it, and the pulmonary arteries.The cause is unknown.
People may have general symptoms, such as...
Churg-Strauss
Syndrome
Apr 1, 2008
Churg-Strauss
syndrome is inflammation of small blood vessels that damages organs
and that usually occurs in people with a history of asthma, nasal
allergies, or both.The
cause is unknown.
At first, people may have a runny nose or asthma
for months o...
Henoch-Schönlein
Purpura
Apr 1, 2008
Henoch-Schönlein
purpura is inflammation mainly of small vessels, usually occurring
in children.A
rash of reddish purple bumps and spots on the lower legs is usually
the first symptom, followed by joint aches, digestive upset, and
kidney malfunction....
Microscopic
Polyangiitis
Apr 1, 2008
Microscopic
polyangiitis is inflammation of mainly small vessels throughout
the body.People
have a fever, lose weight, and have achy muscles and joints, as
well as various other symptoms depending on the organs affected.
Biopsy is done to confirm the...
Introduction
Apr 1, 2008
The muscles, bursas, tendons,
and bones must be healthy and functioning correctly for the body
to move normally. Muscles, which contract to produce movement, are
connected to the bones by tendons. Bursas are flat sacs containing
joint (synovial) flui...
Muscle
Cramps
Apr 1, 2008
A cramp is
a sudden, brief, usually painful contraction of a muscle or group
of muscles....
Fibromyalgia
Apr 1, 2008
Fibromyalgia
is characterized by poor sleep, fatigue, and widespread aching and
stiffness in soft tissues, including muscles, tendons, and ligaments.Poor sleep, stress, strains,
injury, and possibly certain personality characteristics may increase
th...
Bursitis
Apr 1, 2008
Bursitis is
painful inflammation of a bursa (a flat, fluid-filled sac that provides
cushioning where skin, muscles, tendons, and ligaments rub over
bones).Movement
is painful, and bursas near the skin may become swollen and tender.
Pain around bursas...
Tendinitis
and Tenosynovitis
Apr 1, 2008
Tendinitis is
inflammation of a tendon. Tenosynovitis is tendinitis
accompanied by inflammation of the protective covering around the tendon
(tendon sheath).Tendons
are painful, particularly when moved, and sometimes swollen.
The diagnosis is usually...
Baker's
Cysts
Apr 1, 2008
Baker's cysts
(popliteal cysts) are tiny sacs filled with joint (synovial) fluid
that form in an extension of the joint capsule behind the knee....
Introduction
Apr 1, 2008
Headaches are a very common
medical problem and a common cause of disability among men and women.
Headaches interfere with the ability to work and do daily tasks.
Some people have frequent headaches. Other people hardly ever have
them....
Tension-Type
Headaches
Apr 1, 2008
A tension-type
headache is usually mild to moderate pain that feels like a band
tightening around the head.
Pain in other parts of the head and neck may trigger
these headaches.
Headaches may occur several or many days each month.
Doctors base the di...
Migraines
Apr 1, 2008
A migraine
headache is a pulsating or throbbing pain that usually ranges from
moderate to severe. It can affect one or both sides of the head.
It is worsened by physical activity, light, sounds, or smells and
is accompanied by nausea, vomiting, and s...
Cluster
Headaches
Apr 1, 2008
A cluster
headache causes severe pain that is felt at the temple or around
the eye on one side of the head and that lasts a relatively short time
(usually 30 minutes to 1 hour). Headaches usually occur regularly
during a 1- to 3-month period, followe...
Idiopathic
Intracranial Hypertension
Apr 1, 2008
Idiopathic
intracranial hypertension (benign intracranial hypertension, pseudotumor
cerebri) involves increased pressure within the skull (intracranial
pressure), without any evidence of a cause.People have daily headaches,
sometimes with nausea, blu...
Low-Pressure
Headache
Apr 1, 2008
Low-pressure
headaches result when cerebrospinal fluid is removed during a spinal
tap (lumbar puncture) or leaks out because of a cyst or tear. Loss
of this fluid, which flows around the brain, reduces pressure around
the brain....
Introduction
Apr 1, 2008
Low back and neck pain
are among the most common reasons for health care visits. The pain
usually results from problems with the spine, including the bones
of the spine (vertebrae) and the muscles and ligaments that support
it. Occasionally, low back...
Low
Back Pain
Apr 1, 2008
Common causes include sprains and strains, osteoarthritis,
osteoporosis, a ruptured or herniated disk, fibromyalgia, and, in
older people, spinal stenosis.
Pain may be intermittent or constant, superficial
or deep, or dull or sharp, depending on the...
Neck
Pain
Apr 1, 2008
Neck pain usually results from strains and sprains.
Pain from the neck may shoot down an arm or cause
a headache.
Doctors base the diagnosis on symptoms, results
of a physical examination, and sometimes x-rays or other imaging
tests.
Treatment inclu...
Amyloidosis
Apr 1, 2008
Amyloidosis
is a rare disease in which a protein called amyloid accumulates
in various tissues and organs, impairing normal function.The symptoms and severity
of amyloidosis depend on which organs are affected.
Diagnosis is made by examining a small ...
Introduction
Apr 1, 2008
Imaging tests provide
a picture of the body's interior—of the whole body or part of it.
Most imaging tests are painless, relatively safe, and noninvasive
(that is, they do not require an incision in the skin or the insertion
of an instrument into the...
Angiography
Apr 1, 2008
In angiography, x-rays
are used to produce detailed images of blood vessels. It is sometimes
called conventional angiography to distinguish it from computed
tomography (CT) angiography and magnetic resonance angiography.
During angiography, doctors c...
Computed
Tomography
Apr 1, 2008
In computed tomography
(CT), an x-ray source and x-ray detector rotate around a person.
In modern scanners, the x-ray detector usually has 4 to 64 or more
rows of sensors that record the x-rays that pass through the body.
Data from the sensors repres...
Magnetic
Resonance Imaging
Apr 1, 2008
In magnetic resonance
imaging (MRI), a strong magnetic field and very high frequency radio
waves are used to produce highly detailed images. MRI does not use
x-rays and is usually very safe....
Plain
X-Rays
Apr 1, 2008
X-rays are high-energy
radiation waves that can penetrate most substances (to varying degrees).
In low doses, x-rays are used to produce images that help doctors
diagnose disease. In high doses, x-rays (radiation therapy) is used
to treat cancer. X-r...
Radionuclide
Scanning
Apr 1, 2008
In radionuclide
scanning, radionuclides are used to produce images. A radionuclide
is an unstable atom that becomes more stable by releasing energy
as radiation. Most radionuclides release high-energy photons as
gamma rays (which are similar to x-ray...
Ultrasonography
Apr 1, 2008
Ultrasonography
uses high-frequency sound (ultrasound) waves to produce images of
internal organs and other tissues. A device called a transducer
converts electrical current into sound waves, which are sent into
the body's tissues. Sound waves bounce...
Introduction
Mar 1, 2008
Interstitial lung disease
(also called diffuse parenchymal or infiltrative lung disease) is
a term used to describe a number of different disorders that affect
the interstitial space. The interstitial space consists of the air
sacs of the lungs (alve...
Idiopathic
Interstitial Pneumonias
Mar 1, 2008
Idiopathic
interstitial pneumonias are interstitial lung diseases that have
no known cause and that affect the lungs similarly....
Pulmonary
Langerhans' Cell Granulomatosis
Mar 1, 2008
Pulmonary
Langerhans cell granulomatosis (histiocytosis or eosinophilic granuloma)
is a disorder in which cells called histiocytes and eosinophils
proliferate in the lung, often causing scarring....
Lymphoid
Interstitial Pneumonia
Mar 1, 2008
Lymphoid interstitial
pneumonia is an uncommon lung disease in which mature lymphocytes
(a type of white blood cell) accumulate in the alveoli....
Sarcoidosis
Mar 1, 2008
Sarcoidosis
is a disease in which abnormal collections of inflammatory cells
(granulomas) form in many organs of the body....
Pulmonary
Alveolar Proteinosis
Mar 1, 2008
Pulmonary
alveolar proteinosis is a rare disorder in which the air sacs of
the lungs (alveoli) become plugged with a protein-rich fluid....
Pulmonary
Hypertension
Mar 1, 2008
Pulmonary
hypertension is a condition in which blood pressure in the arteries
of the lungs (the pulmonary arteries) is abnormally high....
Lung
Cancer
Mar 1, 2008
Cigarette smoking is the most common cause of lung
cancer.
One common presenting symptom is a persistent cough.
Chest x-rays can detect most lung cancers, but other
additional imaging tests and biopsies are needed.
Surgery, chemotherapy, targeted a...
Osteonecrosis
Mar 1, 2008
Osteonecrosis,
also referred to avascular necrosis of bone, aseptic necrosis, ischemic
necrosis, or osteochondritis dissecans, is the death of a segment
of bone caused by an impaired blood supply....
Introduction
Mar 1, 2008
A number of different
disorders may affect the hands, including ganglia, deformities,
disorders related to nerves or blood vessels, injuries, and infections.
Some other disorders that affect the hands are covered elsewhere
in the book, including frac...
Ganglia
Mar 1, 2008
Ganglia (ganglion
cysts) are gelatinous swellings on the hands and wrists....
Deformities
Mar 1, 2008
Hand deformities may be
caused by an injury or may result from another disorder (for example,
rheumatoid arthritis—see ). Deformities should be treated promptly,
if possible. Otherwise, they tend not to respond to simple treatments,
such as splinting...
Nerve
Compression Syndromes
Mar 1, 2008
Carpal tunnel syndrome,
cubital tunnel syndrome, and radial tunnel syndrome are nerve compression
syndromes. In these disorders, something (usually bone or connective
tissue) presses on a nerve, causing abnormalities of sensation,
movement, or both. ...
Kienböck's
Disease
Mar 1, 2008
Kienböck's
disease is the death of bone tissue due to an impaired blood supply
(avascular necrosis—see ) affecting the lunate bone in the
hand....
Injuries
Mar 1, 2008
Hand injuries cause swelling,
pain, stiffness, and sometimes limited movement. The most common
injuries are tears (ruptures) of ligaments or fractures of bone.
When a ligament is ruptured, bones can move out of position, resulting
in a dislocated joi...
Infections
Mar 1, 2008
Human and animal bites
can cause an infection of the hands. Some other infections are felon
and herpetic whitlow. Paronychia is discussed elsewhere (see )....
Introduction
Mar 1, 2008
Some foot problems start
in the foot itself, for example, from a foot injury. Others result from
disorders that affect many parts of the body, such as diabetes,
gout, or other types of arthritis. Problems can occur in any bone, joint,
muscle, tendon,...
Pain
in the Ball of the Foot (Metatarsalgia)
Mar 1, 2008
Pain in the ball of the
foot (called metatarsalgia) may have many different causes (including
arthritis, poor circulation, pinching of the nerves between the
toes, posture problems, and various disorders). However, most often
the pain is caused by ne...
Tarsal
Tunnel Syndrome
Mar 1, 2008
Tarsal tunnel
syndrome (posterior tibial neuralgia) is pain in the ankle, foot,
and toes caused by compression of or damage to the nerve supplying
the heel and sole (posterior tibial nerve)....
Medial
Plantar Nerve Entrapment
Mar 1, 2008
Medial plantar
nerve entrapment is compression of a nerve at the inner heel (the
medial plantar nerve) that causes pain, numbness, or tingling....
Tibialis
Posterior Tendinosis
Mar 1, 2008
Tibialis posterior
tendinosis is wear and tear of a tendon that passes behind and around
the inner ankle....
Plantar
Fasciosis
Mar 1, 2008
Plantar fasciosis
is pain originating from the dense band of tissue called the plantar
fascia that extends from the bottom of the heel bone to the base
of the toes (ball of the foot)....
Inferior
Calcaneal Bursitis
Mar 1, 2008
Bursitis is painful inflammation
of a bursa (a flat sac containing joint [synovial] fluid that reduces
friction in areas where skin, muscles, tendons, and ligaments rub
over bones). Bursitis can develop at the bottom of the heel. The heel
may throb, ...
Achilles
Tendon Bursitis
Mar 1, 2008
Achilles tendon
bursitis is inflammation of the fluid-filled sac (bursa) located
either between the skin of the heel and the Achilles tendon (posterior
Achilles tendon bursitis) or in front of the attachment of the Achilles
tendon to the heel bone (a...
Achilles
Tendon Enthesopathy
Mar 1, 2008
Achilles tendon
enthesopathy is pain where the Achilles tendon attaches to the back
of the heel....
Corns
and Calluses
Mar 1, 2008
Corns are
hard cone-shaped bumps of skin commonly found on the upper surface
of the smaller toes, particularly over a joint. Calluses are
somewhat rounded flat thickenings of the skin located on the under-surface
of the foot....
Bunion
Mar 1, 2008
In bunion,
the joint of the base of the big toe appears to stick out (becomes
prominent)....
Hammer
Toe
Mar 1, 2008
Hammer toe
is a toe that is in a fixed (rigid) contracted position....
Plantar
Fibromatosis
Mar 1, 2008
Plantar fibromatosis
is a noncancerous (benign) growth of connective tissue in the sole (the
plantar fascia)....
Introduction
Mar 1, 2008
Sleep disorders
are disturbances that affect the ability to fall asleep, stay asleep,
or stay awake or that cause abnormal behaviors during sleep, such
as night terrors or sleepwalking....
Insomnia
Mar 1, 2008
Insomnia is
difficulty falling asleep or staying asleep or a disturbance in
sleep quality that makes sleep seem inadequate or unrefreshing.People are sleepy and tired
during the day and have trouble functioning.
Doctors base the diagnosis on a detail...
Circadian
Rhythm Sleep Disorders
Mar 1, 2008
Circadian
rhythm sleep disorders occur when people's internal sleep-wake schedule
(clock) does not align with the earth's cycle of darkness (night)
and light (day).Jet
lag and shift work commonly disturb the usual rhythms of sleep and
waking.
People ...
Hypersomnia
and Excessive Daytime Sleepiness
Mar 1, 2008
Hypersomnia
is a substantial increase in total sleeping time. Excessive daytime
sleepiness (EDS) is the inability to stay awake and alert during
the day, resulting in unintended lapses into drowsiness or sleep....
Narcolepsy
Mar 1, 2008
Narcolepsy
is a sleep disorder marked by excessive sleepiness during the day
or recurring, uncontrollable episodes of sleep during normal waking
hours, plus sudden episodes of muscle weakness (cataplexy). Sometimes sleep
paralysis, vivid dreams, and ...
Periodic
Limb Movement Disorder and Restless Legs
Syndrome
Mar 1, 2008
Periodic
limb movement disorder involves repetitive movements of the arms,
legs, or both during sleep. Restless legs syndrome involves an irresistible
urge to move and usually abnormal sensations in the legs, arms,
or both when people sit still or li...
Parasomnias
Mar 1, 2008
Parasomnias
are unusual behaviors that occur during sleep....
Sleep
Disorders in Dementia
Mar 1, 2008
In people with dementia
(see ),
such as Alzheimer's disease, sleep patterns are often abnormal.
As dementia progresses, the time spent in light sleep increases,
so people are easily awakened.People with dementia may have disorders that
contribute to ...
Introduction
Mar 1, 2008
Brain damage can cause
many types of dysfunction. Such dysfunction ranges from complete
loss of consciousness (as occurs in a coma), to disorientation and
an inability to pay attention (as occurs in delirium), to impairment
of one or several of the m...
Dysfunction
by Location
Mar 1, 2008
Because different areas
of the brain control specific functions (see ), the location of brain damage determines
the type of dysfunction that results. Which side of the brain is
affected is also important because the functions of the two halves
of the...
Specific Types of Dysfunction
Mar 1, 2008
Many functions of the
brain are performed by several areas of the brain working together (networks),
not by a single area in the brain. Damage to these networks can
cause aphasia, apraxia, agnosia, or amnesia....
Seizure Disorders
Mar 1, 2008
In seizure
disorders, the brain's electrical activity is periodically disturbed,
resulting in some degree of temporary brain dysfunction....
Introduction
Mar 1, 2008
Most nerve fibers
inside and outside the brain are wrapped with many layers of tissue composed
of a fat (lipoprotein) called myelin. These layers form the myelin
sheath. Much like the insulation around an electrical wire, the
myelin sheath enables el...
Multiple
Sclerosis (MS)
Mar 1, 2008
In multiple
sclerosis, patches of myelin and underlying nerve fibers in the
eyes, brain, and spinal cord are damaged or destroyed....
Other
Primary Demyelinating Diseases
Mar 1, 2008
...
Introduction
Feb 1, 2008
Coronary artery
disease is a condition in which the blood supply to the heart muscle
is partially or completely blocked....
Angina
Feb 1, 2008
Angina, also
called angina pectoris, is temporary chest pain or a sensation of
pressure that occurs while the heart muscle is not receiving enough
oxygen.A person
with angina has discomfort or pressure beneath the breastbone (sternum).
Angina typical...
Acute
Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable
Angina)
Feb 1, 2008
Acute coronary
syndromes result from a sudden blockage in a coronary artery. This
blockage causes unstable angina or heart attack (myocardial infarction)
depending on the location and amount of blockage.People who experience an acute
coronary syndrom...
Introduction
Feb 1, 2008
Veins return blood to
the heart from all the organs of the body. The large veins parallel
the large arteries and often share the same name, but the pathways
of the venous system are more difficult to trace than those of the
arteries. Many unnamed sma...
Deep
Vein Thrombosis (DVT)
Feb 1, 2008
Deep vein
thrombosis is the formation of blood clots (thrombi) in the deep
veins.Blood
clots may form in veins if the vein is injured, a disorder causes
the blood to clot, or something slows the return of blood to the
heart.
Blood clots may cause the...
Superficial
Thrombophlebitis
Feb 1, 2008
Superficial
thrombophlebitis (superficial phlebitis) is inflammation and clotting
in a superficial vein.The
skin over the vein becomes red, swollen, and painful.
Doctors examine the area, but tests are not usually
needed.
People may need to take anal...
Varicose
Veins
Feb 1, 2008
Varicose
veins are abnormally enlarged superficial veins in the legs.Varicose veins may ache or
cause itching or a sensation of tiredness.
Doctors can detect varicose veins by examining the
skin.
Surgery or injection therapy can remove varicose
veins...
Arteriovenous
Fistula
Feb 1, 2008
An arteriovenous
fistula is an abnormal channel between an artery and a vein.Although doctors may be able
to hear the distinctive sound of blood flow though a fistula by
using a stethoscope, imaging tests are often needed.
Fistulas can be cut out or ...
Introduction
Feb 1, 2008
Like the venous system,
the lymphatic system transports fluids throughout the body. The
lymphatic system consists of thin-walled lymphatic vessels, lymph
nodes, and two collecting ducts (see ). Lymphatic
vessels, located throughout the body, are larg...
Lymphedema
Feb 1, 2008
Lymphedema
is the accumulation of lymph resulting in swelling....
Bronchiectasis
Feb 1, 2008
Bronchiectasis
is an irreversible widening (dilation) of portions of the breathing
tubes or airways (bronchi) resulting from damage to the airway wall....
Introduction
Feb 1, 2008
The pleura
is a thin, transparent, two-layered membrane that covers the lungs
and also lines the inside of the chest wall. The layer that covers
the lungs lies in close contact with the layer that lines the chest
wall. Between the two thin flexible l...
Pleural
Effusion
Feb 1, 2008
Pleural effusion
is the abnormal accumulation of fluid in the pleural space.Fluid can accumulate in the
pleural space as a result of a large number of disorders, including
infections, injuries, heart or liver failure, blood clots in the
lung blood ve...
Pneumothorax
Feb 1, 2008
A pneumothorax
is the presence of air between the two layers of pleura, resulting
in partial or complete collapse of the lung.Symptoms include difficulty
breathing and chest pain.
Diagnosis is by chest x-ray.
Treatment is usually draining the air wit...
Viral
Pleuritis
Feb 1, 2008
Viral pleuritis
is a viral infection of the pleurae, which typically causes chest
pain when breathing or coughing....
Osteoporosis
Feb 1, 2008
Osteoporosis
is a condition in which a progressive decrease in the density of
bones weakens the bones, making fractures likely....
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