(Redirected from Vitamin B3 deficiency)


  • Pellagra is the deficiency of Niacin (Vitamin B3).
  • Niacin is an important factor for the production of NADH and NADPH, which are important for redox reactions.
    • Deficiency therefore affects tissues with high turnover, including skin, GI tract and brain
  • Niacin is either consumed in the diet or converted from tryptophan by the hepatic kynurenine pathway in the liver.
  • Neurological symptoms can also be exacerbated by supplementation by other B vitiamins, particularly B1, B2, B6, and B12. Mechanism is unknown but may be secondary to the increased demand of NAD.

Drugs that inhibit niacin production

Conditions that decrease niacin GI absoprtion

Clinical Features

Dermatologic features of pellagra including peeling, redness, scaling, and thickening of sun-exposed areas.
Casal's Necklace in a case of isoniazid-induced pellagra.
Boy with classic pellagra rash.
Pellagra rash that could be confused for sunburn.

Niacin deficiency classically causes the 4 D's: Dermatitis, Diarrhea, Dementia and Death.

  • Skin photosensitivity and rash. Erythematous and scaly. May be mistaken for sunburn.
    • secondary to UV damage and decreased repair and hence the desquamation, keratosis and erythema is most common in sun-exposed skin
    • "Casal's Necklace." Reddish rash surrounding the neck, and on the hands and feet. This is a photosensitivity rash in the exposed areas of the neck. Originally described by Gaspar Casal in 1735.
  • GI symptoms
    • secondary to decreased cell turnover
  • Neurological symptoms
  • Niacin deficiency is often associated with chronic alcohol use secondary to nutritional deficiency and malabsorption.

Differential Diagnosis

Other Rash

Vitamin deficiencies




See Also

External Links


  1. Badaway, Abdulla. “Pellagra and Alcoholism: a biochemical perspective.” Alcohol and alcoholism 2014; vol 49, No 3, pages 238-250
  2. Lopez, Marta, et al. “Pellagra Encephalopathy in the context of alcoholism: review and case report.” Alcohol and alcoholism. Vol 49. No 1. pages 38-41. 2014.