Derm Dx: A girl with cardboard-like skin

Epidermolytic hyperkeratosis (EHK) is an autosomal dominant disorder. It is a type of ichthyosis. The word ichthyosis is derived from the greek work ichthys which means "fish." The ichthyoses are a group of diseases characterized by genetic defects that lead...

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Epidermolytic hyperkeratosis (EHK) is an autosomal dominant disorder. It is a type of ichthyosis.

The word ichthyosis is derived from the greek work ichthys which means “fish.” The ichthyoses are a group of diseases characterized by genetic defects that lead to scaly skin. To the early observers, this scale must have resembled the scale of a fish. 

EHK is also commonly known as bullous congenital ichthyosiform erythroderma (not to be confused with nonbullous congenital ichthyosiform erythroderma). EHK presents shortly after birth with erythema, erosions and blisters. In later infancy and childhood, the blistering component of the disease becomes less prominent as the patient develops extensive hyperkeratosis. 

Hyperkeratosis associated with EHK is thick and may be ridged, horny or spine-like. The flexures show the most severe skin changes, which have been likened to having a corrugated cardboard-like or corduroy fabric-like appearance. EHK is caused by mutations in the genes encoding keratins 1 or 10. 

The pictures presented above are quite typical for EHK, and should not be confused with the other answer choices.

Ichthyosis vulgaris may be congenital or acquired. The congenital variant is autosomal dominantly inherited, and is the most common form of congenital ichthyosis. Onset is in early childhood, at which time fine, grayish scales appear over the entire body with relative sparing of the flexures, such as the antecubital and popliteal fossae. Accentuated skin markings on the palms and significant keratosis pilaris are commonly noted. Eczema is frequently associated with ichthyosis vulgaris. The skin changes improve as the patient ages. 

X-linked ichthyosis affects only males. It is an x-linked condition due to a defect in the gene encoding steroid sulfatase. Affected boys are commonly born via cesarean section since placental sulfatase is required for labor to progress normally. These patients develop scales on their skin that are large and dark. 

The scale frequently affects the neck creating the appearance of a dirty neck. Similar to ichthyosis vulgaris, the antecubital and popliteal fossae are spared. Associations with x-linked ichthyosis include corneal opacities and undescended testes. 

Nonbullous congenital ichthyosiform erythroderma is an autosomal recessive ichthyosis due to mutations in several genes including TGM1, ALOXE3, and ALOX12B.

Infants with nonbullous congenital ichthyosiform erythroderma are born encased in a collodion-membrane. This has a dramatic appearance as if the baby were wrapped tightly in clear plastic wrapping. Shortly after birth, the membrane begins to peel off. When the membrane has completely resolved, the patients are left with reddish skin covered in a very fine whitish scale. 

Diagnosis & Treatment

An EHK diagnosis is based on clinical appearance, family history and biopsy. Families may be referred for genetic counseling, since there is 50% chance that future offspring will inherit the defect. 

Newborns may require close monitoring due to significant blistering and denudation of the skin. As patients age topical emollients, topical keratolytics, and topical and oral retinoids may be tried, but treatment is frequently unsatisfactory.   

Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.