Wednesday, April 8, 2015


Ichthyosiform dermatoses: 

The ichthyosiform dermatoses are a heterogeneous group of disorders presenting with excessive scaling of the skin. The intherited forms of the icthyoses are most common , although the condition can occur secondary to other disease.   

The term ichthyosis is derived from the Greek root ichthy, meaning fish, indicative of the scales on the skin of affected  individuals.

How common are the congenital ichthyoses? How are they inherited?

• Ichthyosis vulgaris: Incidence of 1:250; autosomal dominant
• X-linked ichthyosis: Incidence of 1:6000; X-linked recessive
• Epidermolytic hyperkeratosis: Incidence of 1:300,000; autosomal dominant
• Congenital ichthyosiform erythroderma (CIE): Incidence of 1:100,000; autosomal recessive
• Lamellar ichthyosis: Incidence of 1:300,000; autosomal recessive
• Harlequin fetus: Rare; autosomal recessive
figure:A, Grandfather and granddaughter
with ichthyosis vulgaris. 

B, Palmar hyperkeratosis, a finding often associated with ichthyosis vulgaris. 

C, X-linked ichthyosis, showing characteristic coarse, brown scales. 

D, Young child with congenital ichthyosiform erythroderma demonstrating diffuse erythema and scale.

Ichthyosis vulgaris (Fig. A,B) usually develops around school age, and is characterized by generalized xerosis
and scale, with characteristic sparing of the flexural skin. Additional findings include follicular accentuation (keratosis pilaris), hyperlinearity of palms and soles, and a personal or family history of atopy. Rare patients may have an associated palmar-plantar keratoderma. Skin biopsy demonstrates a decreased granular cell layer associated with moderate hyperkeratosis.

X-linked ichthyosis, in contrast, is usually present by one year of age, affects the posterior neck with “dirty”- appearing scales, and spares the palms and soles (Fig.C). The skin changes—gradually worsening with age— with the neck, face, and trunk ultimately developing thick, brown scales. The disease is caused by a defect in steroid sulfatase, an enzyme important in cholesterol synthesis and vital for normal development and function of the stratum corneum. Accumulation of cholesterol sulfate and a lack of tissue cholesterol ensue, leading to a disturbance in steroid hormone metabolism. Skin biopsy of X-linked ichthyosis is rarely diagnostic, and demonstrates a normal granular layer
with hyperkeratosis.

A collodion baby is a newborn infant whose skin looks like a “baked apple,” with a shiny, tough, membrane-like covering. This term describes a phenotype that occurs in several types of ichthyosis. Although congenital ichthyosiform erythroderma is the most common underlying condition (Fig. 1D), lamellar ichthyosis, Netherton’s syndrome, Conradi’s syndrome and others may also present as a collodion baby. Collodion babies may also go on to have normal skin. These infants are at increased risk for infections and fluid and electrolyte imbalances due to cutaneous fissures and impaired barrier function of the skin. Treatment in a high-humidity environment with frequent application of
petrolatum allows gradual sloughing of the collodion membrane. Manual debridement and keratolytics are not recommended.



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