Review Question - QID 104219

This young man with progressively dry, scaly skin, a history of asthma and keratosis pilaris and a family history of a similar condition, likely has ichthyosis vulgaris.

Ichthyosis vulgaris is an autosomal dominant disorder that causes progressively dry, scaly skin with horny plates over the extensor surfaces of the limbs. This condition generally appears sometime between childhood and young adulthood. Other problems associated with the disorder include a failure to sweat, decreased sensation and joint motion, ectropion, and skin infections.

Koo and Lebwohl discuss the connection between psychological and dermatological conditions. They propose three categories of conditions: psychodermatologic disorders, primary psychiatric disorders and secondary psychiatric disorders. The first encompasses disorders that are made worse by psychological conditions, including stress. The second encompasses disorders that are primarily psychiatric, with self-induced skin manifestations. The last encompasses disorders that are primarily dermatological but cause psychological distress. Ichthyosis falls into this final category.

Thyssen et al. review ichthyosis vulgaris, which is caused by mutations in the filaggrin gene (FLG). The filaggrin protein binds to keratin in epithelial cells. This gene mutation also makes individuals more at risk for other dermatological conditions such as eczema and contact dermatitis. Epidemiologic studies suggest that the prevalence of this disorder is higher in lighter-skinned populations.

Figure A shows the classic appearance of ichthyosis vulgaris. Note the scaly, dry appearance of the skin.

Illustration A shows palms of an individual with ichthyosis vulgaris. Note the hyperlinearity, which can make the hands appear older than they actually are.

Incorrect answers:
Answer 1: Many individuals with ichthyosis vulgaris also suffer from atopic dermatitis, asthma, or allergies. However, atopic dermatitis is characterized by pruritic scaling, hyperpigmentation, and lichenification in flexural areas of the body.
Answer 2: Psoriasis, which also presents in young adulthood, has silvery scale and erythematous patches on extensor surfaces. Arthritis is sometimes also present.
Answer 3: Contact dermatitis presents with a pruritic rash that is in a characteristic distribution (areas where the offending agent came into contact with the skin). This type IV hypersensitivity reaction is acute, not chronic.
Answer 5: Lichen planus is a pruritic inflammatory dermatosis, sometimes associated with HCV, that presents with violceous, flat-topped, polygonal papules. Lesions are often also present on mucosal membranes.