Pellagra Disease is rare and is found in people who eat virtually only maize, for example in parts of Africa. Maize contains niacin in the form of niacytin, which is biologically unavailable, and has a low content of tryptophan. In central America, pellagra has always been rare because maize (for the cooking of tortillas) is soaked overnight in calcium hydroxide which releases niacin. Many of the features of pellagra can be explained purely by niacin deficiency; but some are probably due to multiple deficiencies, including deficiencies of proteins and of other vitamins.
Pellagra may also occur in the following circumstances:
Isoniazid therapy can lead to a deficiency of vitamin B 6 , which is needed for the synthesis of nicotinamide from tryptophan. Vitamin B 6 is now given concomitantly with isoniazid.
In Hartnup's disease, a rare inborn error, in which basic amino acids including tryptophan are not absorbed by the gut. There is also loss of this amino acid in the urine.
In generalized malabsorption (rare).
Alcohol-dependent patients who do not eat.
Very low protein diets given for renal disease or taken as a food fad.
In the carcinoid syndrome and phaeochromocytomas, tryptophan metabolism is diverted away from the formation of nicotinamide to form amines.
Diagnosis of Pellagra
In endemic areas this is based on the clinical features, remembering that other vitamin deficiencies can produce similar changes (e.g. angular stomatitis). Nicotinamide (approximately 300 mg daily by mouth) with a maintenance dose of 50 mg daily is given with dramatic improvement in the skin and diarrhoea. Mostly, however, vitamin B complex is given, as other deficiencies are often present.
An increase in the protein content of the diet and treatment of malnutrition and other vitamin deficiencies is essential.
Vitamin B3 and Pellagra