A case of dowling-degos disease on the vulva.

Dowling-Degos disease (DDD) is an autosomal dominant genodermatosis and this disease is a genetically determined disturbance of epidermal proliferation. It is characterized by acquired, slowly progressive pigmented lesions that primarily involve the great skin folds and flexural areas such as the axilla, neck, limb flexures, the inframammary area and the inguinal folds. The vulva is an unusual location for DDD. A 41-year-old woman presented with a 10-year history of multiple, small, reticulated and brownish macules distributed symmetrically on the bilateral external genital regions. We found no other similarly pigmented skin lesions on her body, including the flexural areas. There was no known family history of similar eruptions or pigmentary changes. The histologic examination showed irregular rete ridge elongation with a filiform or antler-like pattern and basilar hyperpigmentation on the tips. Fontana-Masson staining showed increased pigmentation of the rete ridges and the S100 protein staining did not reveal an increased number of melanocytes in the epidermis. From these findings, we diagnosed this lesion as DDD.