Pellagra

Background

• 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

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

Conditions that decrease niacin GI absoprtion

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

Clinical Features

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

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
  • "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
  • "Pellagra encephalopathy," depression, anxiety, altered mental status, hallucinations, delusions, affective disorders, cognitive dysfunction.

• Niacin deficiency is often associated with chronic alcohol use secondary to nutritional deficiency and malabsorption.

Differential Diagnosis

Other Rash

• Acute generalized exanthematous pustulosis
• Allergic reaction
• Aphthous stomatitis
• Atopic dermatitis
• Coxsackie
• Dermatitis herpetiformis
• Exfoliative erythroderma
• Impetigo
• Pellagra
• Pityriasis rosea
• Serum Sickness
• Tinea capitus
• Tinea corporis
• Vitiligo

Management

Niacin supplementation.

References

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.