Ultrastructure of Early Pigmentary Changes in Dowling‐Degos' Disease*

Abstract

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 yr old girl an EM 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.