Macromelanosomes in the early diagnosis of neurofibromatosis.

Skin biopsies of café-au-lait macules from 34 patients with a clinical diagnosis of classical neurofibromatosis were examined histologically and ultrastructurally to determine the presence or absence of macromelanosomes in the epidermal melanocytes and keratinocytes. Sixteen of the 34 patients had macromelanosomes. The presence of macromelanosomes varied with age and ethnic background; they were detected in nine of 12 Whites, six of 10 persons of mixed ancestry, and one of two Blacks. In these populations skin biopsy is useful in early diagnosis of neurofibromatosis. However, none of 10 persons of Indian stock had macromelanosomes. Their total absence in this group may be indicative of genetic heterogeneity.