Recognizing pellagra with Casal's necklace: a fatal case of anorexia nervosa.

Pellagra is a nutritional deficiency caused by the inadequate intake or metabolism of niacin (vitamin B3) and its precursor tryptophan. While pellagra is now rare in developed countries, individuals with eating disorders such as anorexia nervosa or chronic alcoholism remain at risk of developing this condition. We report a fatal case of pellagra in a woman with anorexia nervosa. Autopsy revealed severe emaciation, Casal's necklace, and additional cutaneous findings, including Russell's sign. Histopathological examination of the neck lesion revealed characteristic psoriasiform changes. Postmortem serum analysis revealed a markedly reduced tryptophan concentration (16.1 nmol/mL; reference range: 40.9-68 nmol/mL), consistent with the diagnosis of pellagra. This case highlights the diagnostic importance of integrated histopathology, cutaneous findings, and postmortem serum amino acid profiling in identifying fatal nutritional deficiencies. Furthermore, it emphasizes the need to consider pellagra in at-risk populations, even in modern forensic settings.