Pellagra-like Photosensitive Dermatitis due to Niacin Deficit

This post is an answer to the Case – Vitamin Deficiency

An 88-year-old man with long-standing obstructive lung disease was admitted to the intensive care unit with pneumonia and acute respiratory failure requiring mechanical ventilation.

He was noted to have a symmetric, scaly, sunburn-like, hyperpigmented rash extending from his hands to a clearly demarcated border midway up the arm, suggesting a photosensitive distribution in a patient accustomed to wearing short sleeves. He had no history of diarrhea or dementia before his admission. Dietary habits were reported to be poor.

Serum niacin levels were low (<0.5 ng per milliliter; normal range, 0.5 to 15 ng per milliliter), and a cutaneous biopsy showed parakeratosis, epidermal necrosis, and lymphocytic infiltrates. These findings suggested a diagnosis of pellagra-like dermatitis.

Classic pellagra manifestations include dermatitis, dementia, and diarrhea. If not treated, the condition may have a fatal outcome. In this case, there was substantial improvement in the cutaneous lesions over several days of niacin supplementation.