Dowling-Degos disease involving the vulva and back: case report and review of the literature.

Dowling-Degos disease is a rarely encountered pigmentary disorder in which small brown-to-black macules appear in a clustered or reticulated pattern primarily at flexural sites. It usually occurs as an autosomal dominant trait but sporadic cases have also been reported. Dowling-Degos disease is sometimes associated with other cutaneous abnormalities, many of which appear to occur as a result of abnormal follicular development. The histology is distinctive with marked, heavily pigmented, slender, and often branched, elongation of the rete ridges. Dowling-Degos disease is caused by one of several loss-of-function mutations in the keratin 5 gene. Similar mutations are found in patients with Galli-Galli disease and that disorder is now considered to be a subset of Dowling-Degos disease. Medical therapy is ineffective but two patients have responded well to ablative laser therapy. We report a patient with the sporadic form of the disease who developed pigmented macules in the rarely involved sites of the lower back and vulva. Her vulvar lesions were treated with Er:YAG laser ablation.