A 34-year-old previously well woman presented with a 4-week history of diffuse erythema and crusting of skin affecting all four limbs. Examination revealed erythematous skin plaques associated with ulceration and fissuring affecting sun-exposed areas of all four limbs primarily on the dorsal surfaces, and a body mass index of 17 kg/m 2. She was admitted under the infectious diseases unit, and an autoimmune and infective screen was performed which returned unremarkable. Dietetic consultation led to the diagnosis of severe protein-energy malnutrition, consequent to a severely restricted, primarily vegan, diet. Analysis of the patient’s reported diet with nutritional software revealed grossly suboptimal caloric intake with risk of inadequacy for most micronutrients, vitamins and minerals, including niacin. Oral thiamine, multivitamin, iron supplementation and vitamin B complex were started, and a single intramuscular vitamin B 12 dose was administered. Marked improvement was seen after 6 weeks, with near-complete resolution of skin changes. These findings supported a diagnosis of pellagra.