Niacin (nicotinic acid) deficiency (pellagra) is rare today but can occur in patients with one or more risk factors.
Conditions associated with niacin deficiency:
(1) decreased intake of tryptophan or niacine (nutritional)
(2) decreased conversion of precursors to nicotinic acid or nicotinamide (pathway inhibition)
Conditions associated with a decreased intake of niacin or tryptophan:
(1) diet low in niacin (limited to cultures whose diet consists mostly of millet or maize)
(2) alcohol abuse
(3) Crohn's disease (defective absorption of tryptophan)
Conditions associated with an inhibition in the metabolic pathway:
(1) therapy with isoniazid (INH) and certain other drugs
(2) deficiency of pyridoxine (vitamin B6)
(3) riboflavin deficiency (vitamin B2)
(4) copper deficiency
(5) Hartnup disease
(6) alcohol abuse
