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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), the mildest form of ichthyosis, is neither inherited nor associated with systemic abnormalities. It usually occurs on the lower legs of middle-aged or older patients, most often during cold weather and in those who bathe too frequently. There may be mild to moderate itching and an associated dermatitis caused by detergents or other irritants.
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). 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 flexors; 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
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
In any ichthyosis, minimizing bathing or showering is helpful. Soaps should be used only in intertriginous areas. 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 caused by an underlying systemic disease may slightly improve with lubrication using propylene glycol. However, improvement is greatest if the primary disease can be corrected.
To remove the scale in inherited ichthyoses, patients can apply a preparation containing 50% propylene glycol in water under occlusion (eg, thin plastic film or bags) every night after hydration of the skin. In children, the propylene glycol preparation should be applied bid without an occlusive dressing overnight. After scaling has decreased, less frequent application is required. Other useful agents include 6% salicylic acid gel, hydrophilic petrolatum and water (in equal parts), and cold cream and the α-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.
Patients with epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma) 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. Regular use of soaps containing chlorhexidine may also reduce the bacteria but tend to dry the skin.
Oral synthetic retinoids are effective for most ichthyoses. Acitretin (see Psoriasis and Scaling Diseases: Systemic treatments) is effective in X-linked ichthyosis and epidermolytic hyperkeratosis. 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.)
Last full review/revision November 2005
Content last modified November 2005
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