A 27-Year-Old Man With Hyperpigmented Patches at Upper Back and Limbs

Abstract

27-year-old Asian man presented with a flat patch of darkened skin on his upper back between his shoulder blades. He had a history of intense pruritus for the last 8 years, and the patch developed within the preceding 5 years. The patient also had a history of scratching all over his body, especially over his back using his fingernails. His past medical history was insignificant, except for history of psoriasis involving his thumbs for the past 2 years. On examination, a 20-cm, wing-shaped, flat, dusky brown patch was evident on his upper back between his shoulder blades (Figure 1). The rash first appeared at the nape of his neck and subsequently spread to his shoulders. Clusters of densely packed, 0.5- to 1-mm, flattened, hyperpigmented macules imparted a rippled appearance. These skin changes were present bilaterally on the patient’s shoulders, upper chest, dorsal aspect of arm and forearm, and ventral aspects of thighs and shins. The patient’s palms, soles, and oral mucosa were spared. The rest of the systemic examination was unremarkable. Complete blood count was essentially unremarkable. Blood chemistry profile and coagulation panels were normal. Serum protein electrophoresis did not show a monoclonal spike. A skin biopsy of the hyperpigmented patch at the shoulder was taken. Histologically, patchy basal melanosis and clumps of acellular hyaline amorphous material were evident within the papillary dermis. Special stains were performed, which showed positivity for Sirius red (Figure 2). A panel of monoclonal antibodies was applied using envision technique; the panel showed positivity for cytokeratin MNF (Figure 3). What is your diagnosis?