Pellagra: Clinical Features and Causes

Study Notes

Synthesis: Can be synthesized in humans from tryptophane, with the presence of vitamin B6
Food sources: Found in plants, meat, and fish; lost when bran is removed from cereals, but added to processed cereals and white bread
Importance: Essential in many oxidative processes in the body, particularly in NAD and NADP

Definition: A rare disease caused by niacin deficiency
Causes:
- Maize eating population due to maize's deficiency in nicotinic acid and tryptophan
- Hartnup's disease, a rare inborn error of metabolism
- Generalized malabsorption
- Very low protein diet in renal or liver disease
- Carcinoid syndrome and pheochromocytoma, which divert tryptophane metabolism away from nicotinamide formation
- INH therapy, which can lead to vitamin B6 deficiency
Clinical features:
- Dermatitis, often symmetrical, affecting sun-exposed areas, with redness, cracks, and occasional ulceration
- Diarrhea, with possible constipation, and gastrointestinal manifestations (painful red tongue, glossitis, angular stomatitis, achlorhydria)
- Dementia, with depression, apathy, and thinking disorders in mild cases, and tremors, encephalopathy, and acute psychosis in severe cases
Diagnosis: Based on clinical features, with laboratory tests for RBC NAD levels
Treatment:
- Nicotinamide 100 mg every 6 hours orally
- Protein-rich diet
- Treatment of underlying conditions

Sources: Widely distributed in plants and animal cells, with good sources including dairy products and leafy vegetables
Function: Cofactor for many oxidative reactions in cells
Deficiency:
- Angular stomatitis or cheilosis (fissuring of the corners of the tongue)
- Glossitis (red, inflamed tongue)
- Seborrhoeic dermatitis (particularly in the face)
- Conjunctivitis with vascularization of the cornea and lens opacities
Treatment: Riboflavin 5 mg TDS daily, usually given as part of vitamin B complex

Function: Important cofactor in CHO metabolism, oxidation of acetyl-CoA in the mitochondria, Kreb's cycle, and HMP shunt
Sources: Found in cereals, grains, beans, nuts, and duck
Deficiency:
- Beriberi
- Seen in starved patients, particularly those with cancer, and those with severe hyperemesis, especially when treated with fluids only
Types of Beriberi:
- Dry Beriberi: Polyneuropathy and encephalopathy
- Wet Beriberi: Oedema in the legs, extending to involve the whole body, with ascites and pleural effusion, due to accumulation of lactic and pyruvic acid
- Cardiomyopathy and subsequent heart failure, with a high-output state
Diagnosis:
- Suspected in endemic areas
- Treatment with thiamine and rapid disappearance of oedema is diagnostic
- Confirmed by measurement of transketolase activity in RBCs
- Elevated plasma pyruvate and lactic acids in acute forms of thiamin deficiency
Treatment: Thiamine 50 mg IM for 3 days, followed by 10 mg TDS daily by mouth