The thought that our case could as well represent the uncommon but well-studied nicotinamide deficiency state is provocative and indicates the difficulty in proving any one clinical diagnosis to the exclusion of others—in this case, the diagnosis of pellagra to the exclusion of zinc deficiency, and vice versa.When the pellagra rash appears with the classic long-standing dirtybrown, rough, scaly appearance with associated diarrhea and dementia, a clinical diagnosis can frequently be made. With decreased renal excretion of N-methyl nicotinamide and 6-pyridone derivative, the measurement of which was considered but not done in this case, the diagnosis is confirmed. With resolution of symptoms after a trial of nicotinic acid supplement, which produced no change in this patient, the proof is complete.Due to the lack of diarrhea, a rash that was not suggestive of pellagra, and absent response to multivitamins on admission, the zinc therapy was attempted. This
Ecker RI, Schroeter AL. Zinc Deficiency, Pellagra, or Both?-Reply. Arch Dermatol. 1979;115(4):507–508. doi:10.1001/archderm.1979.04010040079029
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