niacindeficiency

Niacindeficiency, also known as niacin deficiency or pellagra, is a nutritional disorder resulting from insufficient intake of niacin (vitamin B3) or its precursor tryptophan, or from impaired absorption or metabolism of these nutrients. It can occur in contexts of extreme caloric restriction, poor diet, or conditions that disrupt nutrient absorption. In modern developed countries it remains relatively uncommon but can appear in malnourished individuals, certain social groups, or with specific medical problems.

The classic presentation is defined by the four Ds: dermatitis, diarrhea, dementia, and, if untreated, death. Dermatitis is often photosensitive, producing a pigmented, scaly rash in sun-exposed areas. Gastrointestinal symptoms include loss of appetite, abdominal pain, and diarrhea. Neurologic and mental status changes range from irritability and apathy to confusion, memory problems, and mood changes. Additional signs can include glossitis, stomatitis, weakness, and weight loss.

Causes include very low dietary intake of niacin and tryptophan (common in maize-based diets without processing that enhances niacin bioavailability), chronic alcohol use, malabsorption syndromes (such as Crohn's disease or celiac disease), Hartnup disease, carcinoid syndrome, and certain medications (for example, isoniazid). Risk is higher in the elderly, refugees, and people with chronic illnesses.

Diagnosis is primarily clinical, supported by history and response to therapy. Laboratory tests, when used, can measure niacin or its metabolites, but are not routinely required.

Treatment involves niacin supplementation (nicotinamide or nicotinic acid) and addressing underlying causes. Typical therapeutic regimens provide higher daily doses than dietary recommendations, along with dietary improvements. With prompt treatment, symptoms often improve within weeks; without intervention, the condition can be fatal. Prevention focuses on a balanced diet and, in at-risk populations, food fortification and public health measures.