Merck Manual

Please confirm that you are a health care professional

honeypot link

Niacin Deficiency

(Pellagra)

By

Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last review/revision Nov 2022
View Patient Education
Topic Resources

Dietary niacin deficiency (causing pellagra) is uncommon in countries with low rates of food insecurity. Clinical manifestations include the three Ds: localized pigmented rash (dermatitis); gastroenteritis (diarrhea); and widespread neurologic deficits, including cognitive decline (dementia). Diagnosis is usually clinical, and dietary supplementation (oral or, if needed, intramuscular ) is usually successful.

Niacin (nicotinic acid, nicotinamide) derivatives include nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are coenzymes in oxidation-reduction reactions. They are vital in cell metabolism.

Dietary sources of niacin include liver, red meat, fish, poultry, legumes, and whole-grain or enriched cereals and breads. Because dietary tryptophan can be metabolized to niacin, foods rich in tryptophan (eg, dairy products) can compensate for inadequate dietary niacin.

Etiology of Deficiency

Primary niacin deficiency results from extremely inadequate intake of both niacin and tryptophan, which usually occurs in areas where maize (Indian corn) constitutes a substantial part of the diet. Bound niacin, found in maize, is not assimilated in the gastrointestinal tract unless it has been previously treated with alkali, as when tortillas are prepared. Corn protein is also deficient in tryptophan. The high incidence of pellagra in India among people who eat millet with a high leucine content has led to the hypothesis that amino acid imbalance may contribute to deficiency. Deficiencies of protein and many B vitamins commonly accompany primary niacin deficiency.

Symptoms and Signs of Deficiency

Pellagra is characterized by skin, mucous membrane, central nervous system, and gastrointestinal symptoms. Advanced pellagra can cause a symmetric photosensitive rash, stomatitis, glossitis, diarrhea, and mental aberrations. Symptoms may appear alone or in combination.

Skin symptoms include several types of lesions, which are usually bilaterally symmetric. The distribution of lesions—at pressure points or sun-exposed skin—is more pathognomonic than the form of the lesions. Lesions can develop in a glovelike distribution on the hands (pellagrous glove) or in a boot-shaped distribution on the feet and legs (pellagrous boot). Sunlight causes Casal necklace and butterfly-shaped lesions on the face.

Skin Manifestations of Pellagra

Mucous membrane symptoms affect primarily the mouth but may also affect the vagina and urethra. Glossitis and stomatitis characterize acute deficiency. As the deficiency progresses, the tongue and oral mucous membranes become reddened, followed by pain in the mouth, increased salivation, and edema of the tongue. Ulcerations may appear, especially under the tongue, on the mucosa of the lower lip, and opposite the molar teeth.

Gastrointestinal symptoms early in the deficiency include burning in the pharynx and esophagus and abdominal discomfort and distention. Constipation is common. Later, nausea, vomiting, and diarrhea may occur. Diarrhea is often bloody because of bowel hyperemia and ulceration.

Central nervous system symptoms include psychosis, encephalopathy (characterized by impaired consciousness), and cognitive decline (dementia). Psychosis is characterized by memory impairment, disorientation, confusion, and confabulation; the predominant symptom may be excitement, depression, mania, delirium, or paranoia.

Any relationship between niacin status and hypertension is uncertain.

Diagnosis of Deficiency

  • Clinical evaluation

Diagnosis of niacin deficiency is clinical and may be straightforward when skin and mouth lesions, diarrhea, delirium, and dementia occur simultaneously. More often, the presentation is not so specific. Differentiating the central nervous system changes from those in thiamin deficiency Thiamin Deficiency Thiamin deficiency (causing beriberi) is most common among people subsisting on white rice or highly refined carbohydrates in countries with high rates of food insecurity and among people with... read more is difficult. A history of a diet lacking niacin and tryptophan may help establish the diagnosis. A favorable response to treatment with niacin can usually confirm it.

If available, laboratory testing can help confirm the diagnosis, particularly when the diagnosis is otherwise unclear. Urinary excretion of N1-methylnicotinamide (NMN) is decreased; < 0.8 mg/day (< 5.8 mcmol/day) suggests a niacin deficiency.

Treatment of Deficiency

  • Nicotinamide and other nutrients

Because multiple deficiencies are common, a balanced diet, including other B vitamins (particularly riboflavin and pyridoxine), is needed.

Nicotinamide is usually used to treat niacin deficiency, because nicotinamide, unlike nicotinic acid (the most common form of niacin), does not cause flushing, itching, burning, or tingling sensations. Nicotinamide is given in doses of 250 to 500 mg orally daily.

Key Points

  • Niacin deficiency can cause pellagra, mainly in countries with high rates of food insecurity.

  • Pellagra causes a photosensitivity rash, mucositis, gastrointestinal disturbances, and neuropsychiatric dysfunction.

  • Diagnose clinically if possible.

  • Use nicotinamide to treat the deficiency; a favorable response can confirm the diagnosis.

View Patient Education
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz! 
iOS ANDROID
iOS ANDROID
iOS ANDROID
TOP