Clinical Information

Ichthyosis vulgaris is a common disease with an incidence rate of approximately 1 in 250. It is characterized by palmar hyperlinearity, keratosis pilaris, xerosis, and prominent fine scaling of the extensor surfaces of the extremities, the scalp, central part of the face, and the trunk. The clinical onset typically occurs within the first few years of life. Approximately 37% to 50% of people with ichthyosis vulgaris have atopic diseases and about 8% of patients with atopic diseases have classic features of ichthyosis vulgaris. A large number of epidemiological studies support an increased risk and severity of asthma that occurs in association with atopic disease. Clinical presentation associated with ichthyosis vulgaris can be confirmed by genetic testing.

Ichthyosis vulgaris is caused by loss-of-function alterations in the filaggrin (FLG) gene on chromosome 1q21. Filaggrin is a filament aggregating protein that promotes terminal differentiation of the epidermis and skin barrier formation. This prevents epidermal water loss and inhibits entry of allergens, toxic chemicals, and infectious organisms. Loss of filaggrin expression causes cytoskeletal disorganization leading to clinical phenotype associated with ichthyosis vulgaris. FLG mutations are found in about 7.7% of Europeans and 3% of Asians. However, these mutations appear to be less common in dark-skinned ethnicities. The R501X and 2282del4 are complete loss-of-function mutations accounting for approximately 80% of mutations in the Northern European population. However, they are rarer in the Southern European population. These 2 alterations have been shown to be very strong predisposing factors for atopic diseases. FLG mutations in other ethnicities are different than those found in European-origin populations.

This disease is inherited in a semidominant manner (ie, heterozygotes have either no symptoms or milder ichthyosis vulgaris and homozygotes/compound heterozygotes show marked ichthyosis vulgaris).