Monozygotic twins with congenital guttate leukoderma.

We report here two cases of congenital guttate hypomelanotic macules observed in monozygotic twins. They both have had discrete leukoderma regions in the axillae, inguinal region and lower abdomen since birth. The size and the shape did not change until at least the age of nine. Development of both patients was otherwise normal. The split-DOPA reaction revealed no DOPA-positive melanocytes in the hypomelanotic skin, but electron microscopy revealed melanocytes that were regular but decreased in number. Cytogenetic analysis of the peripheral leukocytes revealed normal female karyotype in both cases. Considering the unique pattern of the leukoderma lesions which occurred in both monozygotic twins, this might be a new clinical entity.