Vitamin B12 Deficiency Anemia

Signs and Symptoms

• Anemia
  • Fatigue, palpitations, skin pallor
• Glossitis
• Neuropsych
  • Symmetric peripheral neuropathy/paresthesias
  • Ataxia/gait abnormalities
  • Memory loss
  • Personality changes
  • Dementia

Causes

• Drugs (metformin, PPI, H2 blocker)
• Malnutrition
  • Alcohol use disorder
  • Dietary restrictions (low in meat and dairy products)
  • Elderly
• Malabsorption
  • Gastric surgery
  • Crohns
  • Celiac
  • Fish tapeworm
• Autoimmune gastritis (Pernicious anemia) most common cause
  • Dx: Anti-intrinsic factor Ab or historically Schilling test

Investigations

• CBC + peripheral smear (hypersegmented neutrophils)
• Serum B12 Level +/- Folate
  • If normal/low-normal but still suspect (eg. macrocytic anemia), consider serum methylmalonic acid (MMA)
    • If serum MMA increased, suspect B12 deficiency

Management

• If cause not apparent, consider investigations
  • Consider testing for autoantibodies to intrinsic factor
  • r/o Crohns, celiac, etc...)
• Vitamin B12 1mg (1000mcg) PO daily
  • Lifelong in pernicious anemia
• Consider IM if concerning symptoms, poor compliance, or suspect pernicious anemia
  • 1mg weekly x 1 month then monthly IM or deep SC
• Repeat B12 levels in 1-2d if concerning symptoms, or 2-4w if asymptomatic