A case of multiple keratoacanthoma centrifugum marginatum: response to oral etretinate.

The patient was a 48-year-old man who had a history of colonic polyps. About 18 months before, a dark reddish nodule had appeared on his right forearm. By peripheral growth, this lesion had formed a crateriform prominence with central healing. Similar symptoms multiplied and expanded, the largest being about the size of a child's head. Given both the clinical and histologic evidence, a diagnosis of keratoacanthoma centrifugum marginatum (KCM) was made. Oral etretinate was administered, and an involution of verrucous plaque began after 4 weeks. After 8 weeks, the lesions faded, leaving pigmentation in some areas. This is a rare disorder, only 30 such cases having been reported worldwide, and the present case was the third in which oral etretinate was found to be effective.