Ultrastructure of early pigmentary changes in Dowling-Degos' disease.

Dowling-Degos' anomaly is characterized by a reticular and spotted pigmentation of the skin folds; this pigmentary disturbance, occurring most often in women, is a dominant inherited genodermatosis which worsens progressively and may exhibit in the early phase rapid changes in severity after emotional stress. In a 9-year-old girl, an electonmicroscopic study of pigmented lesions showed a strong melanocytic activity with quantitative increase of the melanosomes; the average size of the melanosomes was not different when compared to normal Caucasoid skin, but in the keratinocytes they were distributed according to a dispersed pattern as in black skin. The pigmentary state of Dowling-Degos' disease is another example of melanocyte-keratinocyte interaction where the epidermal melanin pattern and the size of pigment granules are not in striking correlation. An accelerated rate of melanogenesis and pigmentation may be another factor determining a non-aggregated distribution of the melanosomes within the keratinocytes. The nature of the stimulus of pigmentation in these skin areas which are not sun-exposed is still unclear.