Photoclinic Diagnosis: Plaquelike cutaneous mucinosis

An 18-year-old girl was referred to our department for evaluation and treatment of a single asymptomatic erythematous plaque she had found on her upper back eight months before. She had been treated unsuccessfully with topical corticosteroids. Physical examination revealed an erythematous plaque composed of waxy confluent papules of 2– 3 mm on the upper back. A narrow erythematous ring around the lesion was observed. General physical examination did not reveal any systemic involvement. Medical history revealed treatment of acne vulgaris by isotretinoin (0.5 mg/kg/day) for two months. In her family history, there was no similar disease. Results of laboratory tests including blood count, urinalysis, liver and renal function, and thyroid function were within normal limits. Serum protein electrophoresis did not show any evidence for a monoclonal immunopathy. Screening for viral infections was negative. Dermatophytosis was ruled out by direct microscopic examination and fungal culture tests.