Dyschromatosis universalis hereditaria: an electron microscopic examination.

We report electron microscopic findings from both hyperchromic and achromic macules of dyschromatosis universalis hereditaria (DUH). The keratinocytes of the hyperchromic macules contained numerous, fully melanized melanosomes; almost all of them were aggregated to form the melanosome complex. In contrast, the melanosomes were absent from both keratinocytes and melanocytes of achromic macules, even though intact melanocytes were found. Our results suggest that DUH may be a disorder of melanosome production and distribution in epidermal melanin units rather than a a disorder of melanocyte number.