Acne in Becker's nevus

An 18-year-old man presented with a progressively enlarging, asymptomatic, well-demarcated, irregular, hyperpigmented patch, 13 cm x 11 cm, on the anterior aspect of the chest below the left clavicular region, with a few small macules at the periphery, of 2 years duration. After 18 months, multiple, discrete, erythematous papules and comedones developed over the patch (Fig. 1). A few melanocytic nevi were present in and around the patch. A clinical diagnosis of Becker's nevus with acne vulgaris was made. A skin biopsy from the patch showed acanthosis, elongated rete ridges, increased pigmentation in the basal layer, and a mild perivascular lymphocytic infiltrate in the upper and lower dermis with few melanophages in the dermis. Histopathology of the comedone revealed slight acanthosis, irregular elongation of the rete ridges, and hyperpigmentation of the basal layer of the epidermis. Multiple melanophages were seen in the upper dermis. In the mid-dermis, a ruptured closed comedone was seen. The follicular lumen contained a plug of loosely arranged keratinized cells, sebaceous material, and bacterial colonies. Aggregates of neutrophils were found at the site of rupture of the follicular wall. There was a mild perivascular lymphocytic infiltrate in the upper and lower dermis (Fig. 2). These features confirmed the diagnosis of Becker's nevus with acne vulgaris. The acne was treated with 0.05% tretinoin and 2% erythromycin creams. After 2 months of treatment, all the acne lesions subsided. On further follow-up, the patient had relapse of the acne lesions over the patch with the discontinuation of treatment. A few new lesions also appeared on the face. The treatment was restarted, but the patient was lost to follow-up.