Familial linear and whorled nevoid hypermelanosis.

Two patients with familial linear and whorled nevoid hypermelanosis, a 33-year-old woman and her 3-month-old daughter, are described. These are the first cases of linear and whorled nevoid hypermelanosis of familial occurrence reported in the literature. Asymptomatic hyperpigmented macules in streaky configurations had appeared on the trunk and extremities of both patients several weeks after birth and then gradually spread. No previous inflammation or eruption was observed. Histologic examination revealed a slight increase in the number of melanocytes in the epidermis and an irregular basal melanosis. No pigmentary incontinence or melanophages were observed in the dermis. Ultrastructurally the only finding was an increase in the number of normal-appearing mature melanosomes in keratinocytes in the lesion. Chromosomal analysis of cultured peripheral blood lymphocytes and dermal fibroblasts from normal and pigmented skin revealed no evidence of mixoploidy or chimerism. An undescribed genetic abnormality is suggested as the cause.