Makindo Medical Notes

Related Subjects: |Dementias |Abbreviated Mental Test Score (AMTS)

🧠 Neurological signs of Vitamin B12 deficiency can occur even without anaemia.
💉 Parenteral B12 may reverse peripheral neuropathy, but established spinal cord and brain damage is often irreversible. 📍 Vitamin B12 is actively absorbed in the terminal ileum with the aid of intrinsic factor.

ℹ️ About

• Vitamin B12 deficiency is common and has a wide spectrum of presentations, ranging from anaemia to irreversible neurological damage.
• Deficiency is usually due to malabsorption (e.g., pernicious anaemia, Crohn’s disease, post-gastrectomy) but can also result from strict vegan diets 🌱.
• The liver stores large amounts of B12, so deficiency often develops slowly over several years ⏳.

🥩 Sources of Vitamin B12

• Animal foods: red meat, poultry, fish 🐟, eggs 🥚, and dairy 🧀.
• Fortified foods: cereals, breads, plant-based alternatives 🌾.
• Brewer’s yeast (fortified preparations).

⚠️ Causes

• Pernicious Anaemia: Autoimmune destruction of intrinsic factor ❌.
• Terminal Ileal Disease: Crohn’s disease, ileal resection, ileitis.
• Post-Gastrectomy: Reduced intrinsic factor production.
• Parasites: Diphyllobothrium latum 🪱.
• Bacterial Overgrowth: Competes for B12.
• Strict Vegan Diet: No animal products 🌱.
• Rare: Transcobalamin II deficiency (genetic).

🩺 Clinical Features

• General: Fatigue 😴, lemon-yellow skin, glossitis 👅.
• Oral: Angular cheilitis, beefy sore tongue.
• Neurological:
  • Brain: Dementia 🧠, cerebellar ataxia.
  • Spinal Cord: Subacute combined degeneration →
    • Loss of vibration sense 🎵 and proprioception.
    • Positive Babinski sign 👣.
  • Peripheral Nerves: Tingling/numbness in hands & feet ✋🦶.
  • Ocular: Optic atrophy 👁️.
• Note: Neurological damage may occur without anaemia and can be irreversible ⚡.

🔬 Investigations

• FBC: Macrocytic anaemia (MCV >110 fL), hypersegmented neutrophils 🔍.
• Blood Film: Anisopoikilocytosis.
• Biochemistry: ↑ LDH, ↑ unconjugated bilirubin.
• Specific Tests:
  • Intrinsic factor / parietal cell antibodies (pernicious anaemia) 🧪.
  • Raised methylmalonic acid & homocysteine.
  • Coeliac screen if suspected (anti-TTG).
• MRI: T2 hyperintensity in dorsal columns of cervical cord 📷.

🧾 Differential Diagnosis

• Copper deficiency 🪙: Mimics B12 neuropathy.
• Nitrous oxide abuse 🎈: Inactivates B12.

💊 Management

• Avoid Transfusion: Only in severe cases; risk of cardiac failure ❤️.
• Hydroxocobalamin (IM):
  • 1 mg IM twice weekly × 3 weeks → then every 3 months lifelong (if irreversible cause).
• Folate: Add 5 mg daily if folate deficiency present 🌿.
• Monitor Potassium: Risk of hypokalaemia after replacement 🧂.
• Check Reticulocytes: Rise within 2–3 days ✅.