Severe pellagra masked by concurrent plaque psoriasis: a case report of a hidden diagnosis

Despite characteristic features, psoriasis can mimicother dermatologic conditions, such as seborrheicdermatitis, lichen simplex chronicus, and certainnutritional deficiencies such as pellagra. We present apatient with a longstanding history of severe plaquepsoriasis who presented with disfiguring scaly plaquesinvolving greater than 80% body surface area. Thepatient’s disease was minimally responsive to multipletherapies. Repeat punch biopsies demonstratedparakeratosis, psoriasiform hyperplasia, and dilatedblood vessels consistent with psoriasis. Given atypicalclinical features and overall poor treatment responseadditional work up was obtained. A serum nutritionalpanel was consistent with niacin deficiency andthe patient later revealed extensive alcohol intake.A diagnosis of concurrent pellagra was made andthe patient was started on niacin supplementationand instructed to reduce alcohol intake, whilecontinuing adalimumab and high potency topicalsteroids. Within two weeks, his disease had markedlyimproved. Pellagra presents characteristically with aphotosensitivity dermatitis that may appear clinicallyand histologically similar to psoriasis. It is importantto maintain an index suspicion for a secondarypathology in treatment-resistant psoriasis.