II. Causes

  1. Primary Pellagra
    1. Inadequate Niacin and Tryptophan intake (from meat, dairy, eggs and certain plants)
  2. Secondary Pellagra (conditions interfering with absorption or metabolism or Tryptophan or Niacin)
    1. Anorexia Nervosa
    2. Chronic Diarrhea
    3. Chronic Alcoholism
      1. Most common cause of Pellagra in the United States
    4. Chronic colitis or ileitis (e.g. Inflammatory Bowel Disease) resulting in malabsorption
    5. Cirrhosis
    6. Hartnup Disease
    7. HIV Infection
    8. Malignant Carcinoid Tumor
    9. Medications
      1. Isoniazid (Niacin analog)
      2. Pyrazinamide
      3. Phenobarbitone
      4. 6-Mercaptopurine
      5. Fluorouracil
      6. Phenytoin
      7. Azathioprine

III. Pathophysiology

  1. Results in decreased NAD production
  2. Dermatitis results from poor healing in response to UV light exposure
  3. May be exacerbated by other B Vitamin Deficiencies

IV. Symptoms

  1. Abdominal Pain
  2. Anorexia
  3. Fatigue
  4. Nausea or Vomiting
  5. Watery Diarrhea (Steatorrhea)
  6. Constipation
  7. Mucous membrane inflammation may also be present

V. Signs: Classic Triad ("4Ds")

  1. Diarrhea
  2. Dermatitis
  3. Dementia
  4. Death

VI. Signs: Dermatitis

  1. May be absent despite neurologic changes (esp. chronic Alcoholism)
  2. Early (wet Pellagra)
    1. Sunburn-like skin dermatitis
    2. Erythema in sun exposed areas progresses to overlying vessicles or bullae
  3. Later
    1. Scaly, symmetric red-brown Skin Discoloration involving face, neck (casal necklace), extensor hands/Forearms
    2. Dull red discoloration of nose with yellow Scaling
  4. Other skin and mucosal findings
    1. Alopecia
    2. Beefy red, smooth Glossitis
    3. Edema

VII. Signs: Neurologic changes

VIII. Labs

  1. Avoid lab testing (treat empirically based on symptoms, signs)
  2. Serum Levels (e.g. Niacin, Tryptophan) are typically unreliable
  3. Urine metabolites (e.g. N-methylnicotinamide, 2-pyridone) are unreliable

IX. Management

  1. Precautions
    1. Replacement of other B Vitamins without B3 replacement may exacerbate pellegra encepholopathy
  2. Vitamin B3 replacement
    1. Observe for rapid improvement in symptoms after starting replacement
    2. Initial
      1. Niacinamide 50 mg orally every 6 hours until major signs and symptoms resolve
    3. Next
      1. Niacinamide 50 mg orally every 8-12 hours until skin lesions resolve

X. Complications

XI. References

  1. Jhun et al. in Herbert (2016) EM:Rap 16(9): 8-10
  2. Rendon et al. (2017) Crit Dec Emerg Med 31(6): 15-21
  3. Ghosh (2013) Am Fam Physician 88(7):457-458 [PubMed]

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