B12 Deficiency

Your Path

  • B12 deficiency


  • Affects peripheral nerves
  • Also affects dorsal and lateral columns of spinal cord--> myleopathy
  • Also affects cognitive function, bone marrow


  • Pernicious anemia: an auto-immune process w/anti-bodies directed against the parietal cells--> decreased intrinsic factor--> impaired ability to absorb B12
  • S/p gastrectomy, w/loss of parietal cells
  • Malabsorption: crohn's dz, gastric by-pass, ileal resection (site of b12 absorption in small intestine)
  • Diet related (ie dont consume or have access to B12) or from meds that interfere w/absorption (e.g. PPI, H2 blockers); chronic metformin use; Nitrous oxide abuse ("whippets"), which inactivates B12


  • Gait problems
  • Fatigue
  • Sob w/anemia
  • Progressive numbness
  • Paresthesia which can be painful
  • Affects legs more common then arms
  • Symmetric weakness
  • Confusion/cognitive impairment

Physical Exam Findings

  • Ataxia
  • + rhomberg
  • Tachycardia if sig anemia
  • Tongue can be smooth and swollen if severe
  • Diminished peripheral sensation
  • Impaired proprioception
  • Impaired vibration sense
  • Hyperreflexia (if myelopathy predominates) or hyporeflexia (if PN predominates)
  • Symmetric weakness