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Ichthyosis
is scaling and flaking of skin ranging from mild but annoying dryness
(xeroderma) to severe disfiguring disease (inherited ichthyosis). Ichthyosis
can also be a sign of systemic disease. Diagnosis is clinical. Treatment
involves emollients and sometimes oral retinoids.
Xeroderma:
Xeroderma (xerosis), or dry skin, is neither inherited nor associated with systemic abnormalities. Dry skin results from loss of the water content of the skin, resulting in fine white scales. Risk factors for xerosis include the following:
Inherited ichthyoses:
Inherited ichthyoses, which are characterized by excessive accumulation of scale on the skin surface, are classified according to clinical and genetic criteria (see Table 1: Cornification Disorders: Clinical and Genetic Features of Some Inherited Ichthyoses ). Some occur in isolation without associated abnormalities (eg, ichthyosis vulgaris, X-linked ichthyosis, lamellar ichthyosis, epidermolytic hyperkeratosis [bullous congenital ichthyosiform erythroderma]). Other ichthyoses are part of a syndrome that involves multiple organs. For instance, Refsum's disease (see Inherited Disorders of Metabolism: Classic Refsum's disease) and Sjögren-Larsson syndrome (hereditary mental deficiency and spastic paralysis caused by a defect in fatty aldehyde dehydrogenase) are autosomal recessive conditions with skin and extracutaneous organ involvement. A dermatologist should assist in diagnosis and management, and a medical geneticist should be consulted for genetics counseling.
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Table 1
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Clinical and Genetic Features
of Some
Inherited Ichthyoses
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Disorder
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Inheritance Pattern/ Prevalence
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Onset
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Type of Scale
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Distribution
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Associated Clinical Findings
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Ichthyosis vulgaris
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Autosomal dominant
1:300
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Childhood
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Fine
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Usually, back and extensor surfaces but not flexor surfaces
Usually, many markings on palms and soles
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Atopy
Keratosis pilaris
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X-linked ichthyosis
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X-linked
1:6000 (males)
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Birth or infancy
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Large, dark (may be fine)
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Prominent on neck and trunk
Normal palms and soles
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Corneal opacities
Cryptorchidism
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Lamellar ichthyosis (nonbullous congenital ichthyosiform erythroderma; collodion baby)
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Autosomal recessive 1:300,000
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Birth
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Large, coarse
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Most of body
Thick palms and soles
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Ectropion
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Epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma)
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Autosomal dominant (mutations spontaneous in about 50% of cases)
1:300,000
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Birth
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Thick, warty
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Most of body
Especially warty in flexural creases
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Blisters
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Acquired ichthyosis:
Ichthyosis may be an early manifestation of some systemic diseases (eg, leprosy, hypothyroidism, lymphoma, AIDS). Some drugs cause ichthyosis (eg, nicotinic acid, triparanol, butyrophenones). The dry scaling may be fine and localized to the trunk and legs, or it may be thick and widespread. Biopsy of ichthyotic skin is usually not diagnostic of the systemic disease; however, there are exceptions, most notably sarcoidosis, in which a thick scaling may appear on the legs, and biopsy usually shows the typical granulomas.
Treatment
When ichthyosis is caused by a systemic disorder, abatement is greatest if the primary disease can be corrected. Otherwise, treatment is symptomatic, including using emollients and keratolytics and avoiding drying.
Moisturization
and keratolytics:
In any ichthyosis, there is impaired epidermal barrier function, and moisturizers should be applied immediately after bathing. Substances that are applied to the skin may have increased absorption. For example, hexachlorophene products should not be used because of increased absorption and toxicity.
An emollient, preferably plain petrolatum, mineral oil, or lotions containing urea or α-hydroxy acids (eg, lactic, glycolic, and pyruvic acids), should be applied bid, especially after bathing while the skin is still wet. Blotting with a towel removes excess applied material.
Ichthyosis typically responds well to propylene glycol. To remove scale (eg, if ichthyosis is severe), patients can apply a preparation containing 40 to 60% propylene glycol in water under occlusion (eg, a thin plastic film or bag), every night after hydrating the skin (eg, by bathing or showering); in children, the preparation should be applied twice daily without occlusion. Occlusion should be maintained overnight. After scaling has decreased, less frequent application is required. Other useful keratolytics include ceramide-based creams, 6% salicylic acid gel, hydrophilic petrolatum and water (in equal parts), and the a-hydroxy acids in various bases. Topical calcipotriol cream has been used with success; however, this vitamin D derivative can result in hypercalcemia when used over broad areas, especially in small children.
Retinoids are effective in treating ichthyosis. Oral synthetic retinoids are effective for most ichthyoses. Acitretin (see Psoriasis and Scaling Diseases: Systemic treatments) is effective in treating most forms of inherited ichthyosis. In lamellar ichthyosis, 0.1% tretinoin cream or oral isotretinoin may be effective. The lowest effective dose should be used. Long-term (1 yr) treatment with oral isotretinoin has resulted in bony exostoses in some patients, and other long-term adverse effects may arise. (Caution: Oral
retinoids are contraindicated in pregnancy because of their teratogenicity,
and acitretin should be avoided in women of childbearing potential because
of its teratogenicity and long half-life.)
Infection prophylaxis:
Patients with epidermolytic hyperkeratosis may need long-term treatment with cloxacillin 250 mg po tid or qid or erythromycin 250 mg po tid or qid, as long as thick intertriginous scaling is present, to prevent bacterial superinfection from causing painful, foul-smelling pustules. Regularly using soaps containing chlorhexidine may also reduce the bacteria, but these soaps tend to dry the skin.
Last full review/revision July 2009 by James G. H. Dinulos, MD
Content last modified July 2009
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