Darier-White disease, Keratosis follicularis
Darier disease (DD) is a keratinization disorder characterized by the development of keratotic papules in seborrheic areas and specific nail anomalies. The prevalence is estimated at around 1/50,000. Onset of the disease usually occurs around puberty. Patients present with greasy and colored (yellow-brown or brown) keratotic papules, which may be isolated or grouped forming plaques. The skin lesions often become infected and malodorous, and are responsible for major discomfort. They may be exacerbated by exposure to sunlight or artificial UVB radiation, heat, sweating, friction, and infections. The sites of predilection are the seborrheic areas of the trunk and face: upper chest, back, sides of the neck, forehead, ears, and scalp. The flexures are also frequently involved (the groins, axillae, and anogenital region). Hands and feet may also show discrete papules on the dorsal surfaces. Careful examination of the palms and soles frequently reveals small pits or punctuated keratoses that are highly suggestive, if not specific, of DD. They show the specific combination of red and white longitudinal stripes and present subungual hyperkeratosis. The hard palate, oral mucosa, esophagus, vulva and rectum may be the site of whitish small papules, often densely grouped (leukoplakia). Nail abnormalities are almost constant and highly suggestive. The nails are fragile and have a V-shaped defect. Patients have an increased susceptibility to herpes simplex and pyogenic infections. Severity of the disease is highly variable, even within the same family. DD is caused by mutations in the ATP2A2 gene (12q23-q24.1) encoding a Ca2+ pump of the endoplasmic reticulum. Transmission is autosomal dominant. The diagnosis is based on histological examination of skin lesion biopsies revealing hyperkeratosis, focal dyskeratosis and suprabasal acantholysis. Differential diagnoses include Hailey-Hailey disease, pemphigus and warty dyskeratoma (see these terms), as well as transient acantholytic dermatosis. Genetic counseling should be offered, although prenatal diagnosis is not appropriate in the majority of cases. Management is symptomatic. Patients should avoid sun and heat. Emollients containing urea or lactic acid are of benefit for more limited lesions. Topical application of tretinoin or isotretinoin is effective against hyperkeratosis, but the risk of irritation limits their use. Topical steroids may reduce irritation, but they are not effective when used alone. Retinoids such as tazarotene are better tolerated. In case of severe disease, acitretin (an oral retinoid) is the most effective treatment, but possible side-effects must be monitored. Depression and neuropsychological manifestations have been reported and specific psychological support may be necessary. DD runs a chronic and relapsing course. It may cause considerable social handicap.