How to treat Vitamin B12 (VIT B12) deficiency causing thrombocytopenia?

Treatment of Vitamin B12 Deficiency Causing Thrombocytopenia

Vitamin B12 deficiency causing thrombocytopenia should be treated with intramuscular vitamin B12 injections at a dose of 1000 mcg daily for 6-7 days, followed by alternate day dosing for 7 doses, then every 3-4 days for 2-3 weeks, and finally monthly maintenance of 1000 mcg for life. 1

Diagnosis Confirmation

Before initiating treatment, confirm the diagnosis with:

• Serum vitamin B12 levels:

  • <180 ng/L: Confirmed deficiency
  • 180-350 ng/L: Indeterminate (requires further testing)

  • 350 ng/L: Unlikely deficiency 2

• For indeterminate results, measure:

  • Methylmalonic acid (MMA)
  • Homocysteine levels
  • Complete blood count
  • Folate levels 2

• Look for clinical manifestations:

  • Thrombocytopenia (may present as isolated finding) 3
  • Microangiopathic hemolytic anemia (pseudo-TMA) 4, 5
  • Pancytopenia 6
  • Schistocytes on peripheral smear 4

Treatment Protocol

Initial Treatment Phase

1. Intramuscular B12 administration:

   • 1000 mcg daily for 6-7 days
   • Then 1000 mcg on alternate days for 7 doses
   • Then 1000 mcg every 3-4 days for 2-3 weeks 1

2. Monitoring response:

   • Assess clinical improvement
   • Monitor platelet count recovery
   • Evaluate reticulocyte response 1

Maintenance Phase

• Continue with 1000 mcg monthly intramuscular injections indefinitely 1
• For patients with ileal resection >20 cm, lifelong B12 supplementation is mandatory 7

Special Considerations

Pseudo-Thrombotic Microangiopathy

• B12 deficiency can mimic thrombotic thrombocytopenic purpura (TTP) in approximately 2.5% of cases 4
• Misdiagnosis occurs in up to 40% of cases, leading to unnecessary plasmapheresis 4
• Key distinguishing features:
  • Presence of megaloblastic changes in bone marrow
  • Low serum B12 levels
  • Response to B12 supplementation 6, 5

Route of Administration

• Avoid intravenous administration as most of the vitamin will be lost in urine 1
• Intramuscular route is preferred for initial treatment 1
• Oral supplementation may be considered for maintenance in patients with normal intestinal absorption, but is not reliable for those with pernicious anemia or malabsorption 1

Underlying Causes

Investigate and address underlying causes of B12 deficiency:

• Pernicious anemia
• Ileal disease or resection (>20 cm of distal ileum) 7
• Inflammatory bowel disease, especially Crohn's disease with ileal involvement 7
• Metformin use
• Vegan/vegetarian diet 2

Monitoring and Follow-up

• Monitor platelet count until normalization
• Assess B12 levels periodically during maintenance therapy
• Screen for other potential complications of B12 deficiency:
  • Neurological manifestations
  • Hyperhomocysteinemia 2

Pitfalls to Avoid

1. Misdiagnosing as TTP: This can lead to unnecessary plasmapheresis when B12 supplementation is the appropriate treatment 4, 8

2. Delayed treatment: B12 deficiency left untreated for more than 3 months may cause permanent neurological damage 2

3. Inadequate maintenance: Lifelong supplementation is required for patients with pernicious anemia or significant ileal resection 7, 1

4. Missing concomitant deficiencies: Consider testing and treating folate deficiency, especially in patients on sulfasalazine or methotrexate 7