Ichthyosis nigricans: ultrastructural study of the melanin pigmentary disturbances.

Hyperpigmented skin from a 10-year-old white boy with ichthyosis nigricans has been studied. Histological and ultrastructural studies reveal that the hyperpigmentation is related to both epidermal and dermal hypermelanosis. Melanocytes are hyperactive. The different stages of melanosome synthesis and melanisation appear to be normal. Increased dermal pigmentation probably results from a dischargement of the melanin granules into the dermis secondary to melanocyte alterations. Ichthyosis nigricans is a typical example of melanin pigmentary disturbances of the skin, resulting from disturbances in the normal interactions between melanocytes and keratinocytes.