Histologic examination revealed reticulated acanthosis, with a superficial lymphocytic infiltrate containing melanophages. The acanthosis was characterized by an irregular digitated elongation of thin, branching rete ridges. There was increased melanin concentrated at the tips of the rete ridges. There was also dermal melanosis with melanin-laden melanophages. A variable perivascular lymphohistiocytic infiltrate was evident in the papillary dermis.
Dowling-Degos disease is a rare condition characterized by reticulate hyperpigmented macules affecting flexural areas. It usually presents in adults, most frequently during the fourth decade of life, although cases of childhood onset have been reported as well.1 It is inherited in an autosomal dominant fashion, although sporadic cases have also been reported.2 The lesions are typically numerous small, reticulate, pigmented macules that resemble freckles. The axillae and groin are the most common sites, but other areas may be involved, including the intergluteal and inframammary folds, neck, scalp, trunk, and arms. The lesions are usually symmetrically distributed, progressive, and asymptomatic. Other cutaneous manifestations include perioral pitted scars and comedolike lesions on the neck and back. Occasional cases have been reported with associated hydradenitis suppurativa, trichilemmal cysts, keratoacanthoma, and squamous cell carcinoma.3 The pathogenesis is still unknown, but it has been postulated that DDD may be caused by a single underlying defect in pilosebaceous epithelial proliferation.4