PELLAGRA
Pellagra usually results from a deficiency of nicotinic acid (niacin, vitamin B3) or its precursor amino acid, tryptophan.
Causes:
1. Dietary deficiency: inadequate dietary niacin and/or tryptophan is seen mainly in developing countries or poverty stricken areas. Pellagra is associated classically with a diet almost entirely composed of corn, sorghum, or millet.
2. Chronic alcoholism: the most common cause in the developed countries.
3. Hartnup disease (impaired absorption of tryptophan).
4. Carcinoid tumors, which divert tryptophan to serotonin.
5. GI disorders: Crohn’s disease, ulcerative colitis and GI surgery.
6. Prolonged intravenous supplementation.
7. Psychiatric disorders including anorexia nervosa.
8. Medications: most often isoniazid, azathioprine (and its metabolite 6-mercaptopurine), 5-fluorouracil, ethionamide, and pyrazinamide. Rarely, the anticonvulsants (hydantoins, phenobarbital, and carbamazepine) may produce pellagra.

Clinical features
* Pellagra is a chronic disease affecting the GI tract, nervous system, and skin; thus the mnemonic of the “3 Ds”— diarrhea, dementia, and dermatitis. If left untreated, death is the usual outcome.
* At the onset, the patient has weakness, loss of appetite, abdominal pain, diarrhea (occurs in 50% of cases), mental depression, and photosensitivity.
* Skin lesions may be the earliest sign, with phototoxicity the presenting symptom in some cases.
* Neurologic and GI symptoms can occur without skin changes.
* In the later stages, the neurologic symptoms may predominate. Apathy, depression, muscle weakness, paresthesias, headaches, and attacks of dizziness or falling are typical findings. Hallucinations, psychosis, seizures, dementia, neurologic degeneration, and coma may develop.

* Phototoxic sun burn-like rash occurs on the face, neck, and upper chest (Casal’s necklace), extensor arms and backs of the hands. The rash is usually symmetrical with a clear edge between affected and unaffected skin. There may be itching or a burning sensation.
In severe cases, the eruption may be vesicular or bullous (wet pellagra). After several phototoxic events, thickening, scaling, and hyperpigmentation of the affected skin occur to have a copper or mahogany hue.

* The bridge of the nose is characteristically dull red with fine, yellow, powdery scales over the follicular orifices (sulfur flakes).

Management:
* If the characteristic skin findings are present, the diagnosis of pellagra is not difficult clinically.
* Pellagra can be effectively cured with intravenous or oral niacin or nicotinamide. Nicotinamide, 100 mg three times daily for several weeks, should be given. Within 24-48 h of niacin therapy initiation, the skin lesions begin to resolve, confirming the diagnosis.
* Dietary treatment to correct the malnutrition is essential. A high protein diet supplemented with B-group vitamins is needed for complete recovery.
* Fluid and electrolyte loss from diarrhea should be replaced, and in patients with GI symptoms possibly interfering with absorption, initial IV supplementation should be considered.
* Alcoholism and other factors that may have led to pellagra (secondary pellagra) must be corrected.