Pellagra

Background

Pellagra is the deficiency of Niacin (Vitamin B3). Niacin deficiency classically causes the "3 D's": Dermatitis, Diarrhea and Dementia." 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, thereby causing the "3 D's" mentioned above.

Niacin is either consumed in the diet or converted from tryptophan by the hepatic kynurenine pathway in the liver. Drugs that inhibit the production of niacin via this pathway can also result in pellagra. Such drugs include the following:

• • Azathioprine
  • Chloramphenicol
  • Ethionamide
  • 5-Fluorouracil
  • Isoniazid
  • 6mercaptopurine
  • Pyrazinamide

Conditions that decrease niacin absoprtion from the GI tract can also lead to pellagra and include the following:

• • Colitis
  • Celiac disease
  • Crohn's disease
  • Ulcerative colitis
  • Cirrhosis
  • Gastrectomy patients

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.

Clinical Features

• Skin photosensitivity and rash.
  • secondary to UV damage and decreased repair
  • "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.

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  Casal's Necklace in a case of isoniazid-induced pellagra.

• Example.jpg

  Caption2

• GI symptoms
  • secondary to decreased cell turnover
• Neurological symptoms
  • depression, anxiety, etc.