Niacin Deficiency (Pellagra)
A distinctive dark red rash may appear on the hands, feet, calves, neck, and face. The tongue and oral mucosa can also become dark red.
Niacin deficiency frequently coexists with deficiencies in protein, riboflavin (vitamin B2), and vitamin B6.
Pellagra develops when the diet is deficient in both niacin and tryptophan, an amino acid that the body can convert into niacin.
The condition primarily affects the skin, gastrointestinal tract, and central nervous system.
Pellagra may also develop in the context of:
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Hartnup disease, in which tryptophan absorption is impaired
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Carcinoid syndrome, where tryptophan is diverted toward serotonin synthesis rather than niacin production
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Chronic alcoholism and isoniazid therapy, both of which can interfere with niacin metabolism or availability
Diagnosis is typically based on dietary history and clinical features. Laboratory confirmation may include measuring niacin metabolites in the urine, although this test is not routinely available. A therapeutic trial of niacin that results in symptom resolution can also support the diagnosis.
Treatment:
The preferred treatment is nicotinamide, a form of niacin that does not cause the flushing, itching, burning, or tingling commonly associated with nicotinic acid.
