Background: pellagra is caused by niacin deficiency with niacin being the generic term for both nicotinic acid and nicotinamide. Tryptophan is the amino acid precursor of niacin from which the metabolically active pyridine nucleotides NAD and NADP are formed. Thus, niacin in its metabolically active forms, has a pervasive role in catabolic reactions, particularly in energy-related pathways and biosynthetic processes.

Only small amounts of free niacin occur in nature with most of niacin present in food found as NAD or NADP. Good sources of niacin include meats, fish, legumes and some nuts. In many foods, such as cereals, niacin is of low bioavailability. Thus, pellagra was rampant in maize-eating populations throughout the world (including early 1900’s southeastern US) until its cause was discovered in the 1930’s.

Epidemiology: pellagra has almost disappeared from industrialized countries except for the notable exception of malnourished alcoholics. However, it remains endemic in India as well as parts of China and Africa where corn is a staple, so called cereal pellagra. Other causes of pellagra include prolonged tx. with INH, Hartnups disease and the carcinoid syndrome- all secondary to interference with tryptophan metabolism.

Clinical presentation: remember the three D’s: diarrhea, dementia and dermatitis. The most characteristic sign is a pigmented rash occurring in sun-exposed areas. Color is generally similar to a sunburn, although in chronic cases it make take on a darker color.

Changes in the GI tract are associated with vomiting or diarrhea and the tongue takes on a bright red color.

Neurologic manifestations include anxiety, insomnia, and in more severe cases, disorientation and delusions.

Death occurs within 4 to 5 years if untreated.

Diagnosis and Treatment: the diagnosis is confirmed by demonstration of decreased 24 hour urinary excretion- < 3 mg.

Treatment is with po niacin or nicotinamide 50 mg 10 times per day. In severe cases it can be given IV- 100 mg/d.