Pellagra

Overview

Pellagra is a disease caused by a lack of niacin (vitamin B3) or its building block tryptophan. Niacin is essential for many processes in the body, including energy production and the health of the skin, digestive system, and nervous system.

Pellagra is classically described by the "three Ds": dermatitis, diarrhea, and dementia, and if untreated and severe, it can lead to death. Once common in regions where diets relied heavily on corn (maize) without proper processing, pellagra is now uncommon in places with varied diets. It still occurs, however, in people with poor nutrition, certain medical conditions, or problems absorbing or using niacin. Pellagra responds well to treatment when recognized.

The body can make some niacin from the amino acid tryptophan in protein-rich foods, so pellagra reflects a shortage of both niacin and tryptophan or a problem using them. Because its symptoms develop gradually and can resemble other illnesses, pellagra may be overlooked, particularly in people with alcohol use disorder, malnutrition, or digestive conditions. Recognizing the characteristic combination of skin, digestive, and mental symptoms is important, since treatment is straightforward and effective.

Symptoms

The classic features of pellagra affect the skin, digestive tract, and nervous system:

• Dermatitis: A symmetrical, sometimes scaly or darkened rash, typically on sun-exposed areas such as the hands, arms, face, and neck.
• Diarrhea: Along with other digestive symptoms such as nausea, vomiting, and a sore, red tongue and mouth.
• Dementia or other mental changes: Including confusion, memory problems, irritability, depression, and in severe cases disorientation.

Other symptoms include fatigue, weakness, and loss of appetite. Symptoms often develop gradually and can be mistaken for other conditions.

Causes

Pellagra results from not having enough usable niacin. This can happen for several reasons:

• Dietary deficiency: Diets low in niacin and tryptophan, historically linked to heavy reliance on untreated corn.
• Malabsorption: Digestive conditions that impair nutrient absorption.
• Alcohol use disorder: Which can lead to poor nutrition and reduced niacin intake or use.
• Certain medications and medical conditions: Some drugs and disorders interfere with the body's ability to make or use niacin.

In some cases, an inherited disorder affecting tryptophan handling can also cause pellagra-like symptoms.

Risk Factors

• Diets very low in niacin-rich foods
• Alcohol use disorder
• Conditions that impair nutrient absorption
• Severe eating disorders or food insecurity
• Certain medications that affect niacin metabolism
• Some chronic illnesses

Diagnosis

Pellagra is often diagnosed based on the characteristic symptoms, dietary history, and response to treatment. Evaluation may include:

• Clinical assessment: Recognizing the pattern of skin, digestive, and mental symptoms.
• Dietary and medical history: Looking for poor nutrition, alcohol use, or absorption problems.
• Laboratory tests: To assess nutrition and rule out other causes; a clear improvement with niacin supports the diagnosis.

Treatment

Pellagra is very treatable, and symptoms often improve quickly once niacin is replaced. Treatment includes:

• Niacin replacement: Supplemental niacin (or nicotinamide) given by mouth, or sometimes by injection in severe cases, under medical supervision.
• Improving the diet: A balanced diet with niacin-rich foods and other B vitamins, since deficiencies often occur together.
• Treating the underlying cause: Addressing alcohol use, absorption problems, or medications contributing to the deficiency.
• Skin and supportive care: Protecting affected skin and managing symptoms during recovery.

With treatment, the skin, digestive, and mental symptoms usually improve, though severe or long-standing cases may take longer to recover. Because deficiencies of several B vitamins often occur together, especially with poor nutrition or alcohol use, clinicians frequently address the overall nutritional state rather than niacin alone. Ongoing attention to diet and any underlying cause helps prevent the deficiency from returning.

Prevention

• Eat a varied, balanced diet that includes niacin-rich foods
• Limit or avoid excessive alcohol
• Manage conditions that affect nutrient absorption
• Seek medical advice if you have ongoing poor appetite or weight loss
• Follow guidance on supplementation if you are at higher risk

When to See a Doctor

See a doctor if you notice a symmetrical rash on sun-exposed skin together with persistent diarrhea and mental changes such as confusion or memory problems, particularly with poor nutrition or heavy alcohol use. Seek urgent care if there is:

• Severe confusion, disorientation, or marked behavior change
• Severe or persistent diarrhea with signs of dehydration
• Rapid decline in alertness or overall condition

Related Topics

Frequently Asked Questions

References

1. MedlinePlus, U.S. National Library of Medicine. Niacin deficiency (pellagra).
2. National Institutes of Health (NIH), Office of Dietary Supplements. Niacin.
3. World Health Organization (WHO). Pellagra and its prevention and control.