A 40-year-old man with a 10-year history of plaque psoriasis received oral cyclosporine A treatment for a severe flare of his disease. After approximately 10 days of therapy, he suddenly developed numerous melanocytic nevi in a generalized distribution across both plaque psoriasis–affected and unaffected areas. The nevi had not been present in the previous clinical controls. No psoralen plus UV-A therapy (PUVA) or other light treatments had been used.
Physical examination revealed multiple, light-brown to black pigmented, smooth-surfaced macules measuring from 2 to 4 mm in diameter with a regular outline on the neck, trunk (Figure 1), anterior thighs, palms, and soles. Dermoscopy showed a reticular pattern consisting of a homogeneous brown pigmented network with no dermoscopic background skin pattern. Several of the pigmented macules were examined histologically, and they showed a proliferation of melanocytes at the basal layer of the epidermis with dermal melanophages and nests of normal melanocytes at the dermoepidermal junction. No atypia was observed (Figure 2). A diagnosis of eruptive melanocytic nevi secondary to cyclosporine A was made.