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Pronunciations azathioprine corticosteroid cyclosporine diabetes mellitus methotrexate prednisone

Many disorders, drugs, and other treatments can cause a breakdown in the body's natural defenses. Such a breakdown can lead to infections, which can even be caused by microorganisms that normally live harmlessly on or in the body. A breakdown can result from the following:

• Extensive burns: Risk of infection is increased because damaged skin cannot prevent invasion by harmful microorganisms.
• Medical procedures: During a procedure, foreign material may be introduced into the body, increasing the risk of infection. Such procedures include insertion of a catheter into the urinary tract or a blood vessel and insertion of a tube into the windpipe.
• Drugs that suppress the immune system: These drugs include cancer chemotherapy drugs, drugs used to prevent rejection after an organ transplant (such as azathioprine Some Trade Names
  IMURAN
  , methotrexate Some Trade Names
  TREXALL
  , and cyclosporine Some Trade Names
  NEORALSANDIMMUNE
  ), and corticosteroids (such as prednisone).
• Radiation treatments: Such treatments may suppress the immune system, particularly when bone marrow is exposed to radiation.
• AIDS: The ability to fight certain infections decreases dramatically in people with AIDS, especially late in the disease (see Human Immunodeficiency Virus HIV Infection: Human Immunodeficiency Virus Infection). People with AIDS are at particular risk of opportunistic infections (infections by microorganisms that generally do not cause infection in people with a healthy immune system). People with AIDS also become more severely ill from many common infections.

Spotlight on Aging Infections are more likely and usually more severe in older people than in younger people for several reasons: Aging reduces the immune system's effectiveness (see Biology of the Immune System: Effects of Aging). Many long-term (chronic) disorders that are common among older people—such as chronic obstructive pulmonary disease, cancer, and diabetes mellitus—also increase the risk of infection. Older people are more likely to be in a hospital or a nursing home, where the risk of acquiring a serious infection is greater. In hospitals, the widespread use of antibiotics allows antibiotic-resistant organisms to thrive, and infections with these microorganisms are often more difficult to treat than infections acquired at home.

Last full review/revision October 2008 by Allan R. Tunkel, MD, PhD