Ichthyosis is scaling and flaking of skin ranging from mild but annoying dryness to severe disfiguring disease. Ichthyosis can also be a sign of systemic disease. Diagnosis is clinical. Treatment involves emollients and sometimes oral retinoids.

Ichthyosis differs from simple dry skin (xeroderma—see Cornification Disorders: Xeroderma) by its association with a systemic disorder or drug, inheritability, severity, or a combination. Ichthyosis can also be much more severe than xeroderma.

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 and are not part of a syndrome (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 disease (see Inherited Disorders of Metabolism: Classic Refsum's disease) and Sjögren-Larsson syndrome (hereditary intellectual disability 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 genetic counseling.

Table 1
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Clinical and Genetic Features of Some Inherited Ichthyoses Disorder Inheritance Pattern/ Prevalence Onset Type of Scale Distribution Associated Clinical Findings Ichthyosis vulgaris Autosomal dominant 1:300 Childhood Fine Usually back and extensor surfaces but not intertriginous surfaces Usually many markings on palms and soles Atopy Keratosis pilaris Asthma X-linked ichthyosis X-linked 1:6000 (males) Birth or infancy Large, dark (may be fine) Prominent on neck and trunk Normal palms and soles Corneal opacities Cryptorchidism Testicular cancer Autosomal recessive congenital ichthyosis Autosomal recessive 1:300,000 Birth Large, coarse, sometimes fine Most of body Thick palms and soles Ectropion Epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma) Autosomal dominant (mutations spontaneous in about 50% of cases) 1:300,000 Birth Thick, warty Most of body Especially warty in flexural creases Bullae Clinical and Genetic Features of Some Inherited Ichthyoses Disorder Inheritance Pattern/ Prevalence Onset Type of Scale Distribution Associated Clinical Findings Ichthyosis vulgaris Autosomal dominant 1:300 Childhood Fine Usually back and extensor surfaces but not intertriginous surfaces Usually many markings on palms and soles Atopy Keratosis pilaris Asthma X-linked ichthyosis X-linked 1:6000 (males) Birth or infancy Large, dark (may be fine) Prominent on neck and trunk Normal palms and soles Corneal opacities Cryptorchidism Testicular cancer Autosomal recessive congenital ichthyosis Autosomal recessive 1:300,000 Birth Large, coarse, sometimes fine Most of body Thick palms and soles Ectropion Epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma) Autosomal dominant (mutations spontaneous in about 50% of cases) 1:300,000 Birth Thick, warty Most of body Especially warty in flexural creases Bullae

Acquired ichthyosis: Ichthyosis may be an early manifestation of some systemic disorders (eg, leprosy, hypothyroidism, lymphoma, AIDS). Some drugs cause ichthyosis (eg, nicotinic acid, triparanol, butyrophenones). The dry scale 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 disorder; however, there are exceptions, most notably sarcoidosis, in which a thick scale may appear on the legs, and biopsy usually shows the typical granulomas.

Treatment

• Minimization of exacerbating factors
• Moisturization and keratolytics
• Sometimes infection prophylaxis

When ichthyosis is caused by a systemic disorder, the underlying disorder must be treated for the ichthyosis to abate. Other treatments include 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, hexachloropheneSome Trade Names
PHISOHEX
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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 twice daily, especially after bathing while the skin is still wet. Blotting with a towel removes excess applied material.

Ichthyosis typically responds well to the topical keratolytic 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 worn overnight) every night after hydrating the skin (eg, by bathing or showering); in children, the preparation should be applied twice daily without occlusion. After scale has decreased, less frequent application is required. Other useful topical agents include ceramide-based creams, 6% salicylic acidSome Trade Names
MEDIPLAST
PROPA PH
STRI-DEX
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gel, hydrophilic petrolatum and water (in equal parts), 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.

Retinoids are effective in treating inherited ichthyosis. Oral synthetic retinoids are effective for most ichthyoses. AcitretinSome Trade Names
SORIATANE
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(see Psoriasis and Scaling Diseases: Systemic treatments) is effective in treating most forms of inherited ichthyosis. In lamellar ichthyosis, 0.1% tretinoinSome Trade Names
RETIN-A
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cream or oral isotretinoinSome Trade Names
ACCUTANE
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may be effective. The lowest effective dose should be used. Long-term (1 yr) treatment with oral isotretinoinSome Trade Names
ACCUTANE
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has resulted in bony exostoses in some patients, and other long-term adverse effects may arise.

Pearls & Pitfalls Oral retinoids are contraindicated in pregnancy because of their teratogenicity, and acitretinSome Trade Names SORIATANE Click for Drug Monograph should be avoided in women of childbearing potential because of its teratogenicity and long duration of action.

Infection prophylaxis: Patients with epidermolytic hyperkeratosis may need long-term treatment with cloxacillinSome Trade Names
No US trade name
Click for Drug Monograph
250 mg po tid or qid or erythromycinSome Trade Names
ERY-TAB
ERYTHROCIN
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250 mg po tid or qid, as long as thick intertriginous scale 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.

Key Points

• Ichthyosis may be acquired or inherited as an isolated disorder or as part of a syndrome.
• Evaluate patients with gradual-onset ichthyosis for an underlying systemic disorder.
• Emollients that speed the shedding of skin (keratolytics) are effective in treating ichthyosis.

Last full review/revision March 2013 by James G. H. Dinulos, MD

Content last modified April 2013