Crusted (Norwegian) scabies.

Crusted (Norwegian) scabies, a rare variant of ordinary scabies, is a highly contagious infection in which the skin is infested with thousands to millions of mites. The infection is frequently overlooked because of its atypical presentations. Patients with cognitive deficiency or an immunodeficiency disorder (including immunosuppressive therapy) are predisposed to developing crusted scabies. The infection often presents as generalized dermatitis with crusted hyperkeratosis on the palms and soles. Diagnosis is made by examining skin scrapings from the crusted lesions. Lindane is the scabicide most widely used in the treatment of crusted scabies. Eradication frequently requires repeated applications, and care must be taken to avoid lindane toxicity. Permethrin cream is as efficacious as lindane in the treatment of ordinary scabies. Because of its wider margin of safety, permethrin may become the preferred treatment for crusted scabies.