Progressive macular hypomelanosis.

Progressive macular hypomelanosis (PMH) is a condition of unknown etiology characterized by asymptomatic, hypopigmented macules located predominantly on the trunk. We recorded 12 adolescents with PMH over a 6-month period. Ten were female, and the mean age was 16.6 years. The average time from the patients first noticing pigment change to diagnosis was 15 months. PMH is probably an underdiagnosed condition.