Traditionally caused by consuming a diet mainly composed of corn and maize.
Severe deficiency leads to pellagra, which is characterized by dermatitis, dementia, diarrhea, and eventually death.
Lean meat, poultry, fish, and peanuts are rich in vitamin B3 (niacin); milk and eggs are rich sources of tryptophan, the precursor of niacin.
Deficiency of vitamins B2 (riboflavin) and/or B6 (pyridoxine) reduces the synthesis of niacin from tryptophan and may lead to secondary vitamin B3 deficiency.
Rare in developed countries, although there are still outbreaks in Africa, India, and China, particularly in refugees and displaced people.
In developed countries, deficiency is most commonly associated with chronic alcohol abuse, GI malabsorption, and certain medications (e.g., isoniazid).
As the symptoms of mild vitamin B3 deficiency are similar to those of other B vitamin (e.g., B2 and B6) deficiencies that may coexist, the cause may be difficult to define.
Treatment with niacinamide will alleviate the cutaneous and many neurologic symptoms within 48 hours.
Typical dermatitis of pellagra on sun-exposed skin (extensor aspect of forearm and dorsum of hand) that is clearly demarcated from unexposed skin
From the collection of Demetre Labadarios
- insomnia, depression, or memory loss
- intermittent stupor
- hallucinations or delirium
- peripheral neuropathy
- oppositional hypertonus or myoclonus
- cogwheel rigidity
- primitive reflexes
- nausea, vomiting, or diarrhea
- glossitis, cheilitis, or stomatitis
- anxiety or paranoia
- anorexia, weight loss, or cachexia
- angular palpebritis
1st Tests To Order
- serum tryptophan
- urinary N-methylnicotinamide
- urinary N-methyl-2-pyridone-5-carboxamide
- urinary 2-pyridone/N-methylnicotinamide ratio
- skin biopsy
- photosensitivity testing
- serum albumin
- serum protein
Other Tests to Consider
- serum total iron
- iron-binding capacity
- transketolase activity
- thiamine pyrophosphate (TPP)
- riboflavin coefficient
- serum pyridoxal-5-phosphate
- serum cyanocobalamin
- serum folic acid
- red cell folic acid
- stool exam
- neutral aminoaciduria
- serum serotonin
- platelet serotonin
- urinary 5-hydroxyindoleacetic acid
- HIV antibodies
- mental state exam
asymptomatic (marginal deficiency)
- low-dose niacinamide
- niacinamide + other B vitamins