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PA15.1-3 | Welcome to Vitamin B12 & Folate Metabolism — Deficiency Pathogenesis
Learning Objectives
- Trace the dietary sources and absorption pathway of Vitamin B12, including the role of intrinsic factor and the terminal ileum.
- Outline folate absorption and metabolism, and explain the biochemical relationship between B12 and folate.
- Describe the major causes of B12 deficiency (pernicious anaemia, dietary, malabsorption, drugs) and their mechanisms.
- Explain how impaired DNA synthesis leads to megaloblastosis and nuclear-cytoplasmic asynchrony.
- Justify why neurological involvement (subacute combined degeneration) occurs in B12 deficiency but NOT in isolated folate deficiency.
- Contrast the clinical and biochemical differences between B12 and folate deficiency anemias.
INSTRUCTIONS
Macrocytic anaemia is one of the most nuanced haematological diagnoses in MBBS — because the same blood film can arise from two metabolically distinct deficiencies. This module unpacks the biochemistry and pathology of B12 and folate metabolism so you understand why deficiency causes megaloblastosis and why only B12 deficiency harms the spinal cord. Before you reach the lab module (H4 SDL2) or the smear module (H4 SDL3), you need the molecular foundation built here.
References
- Robbins & Kumar Basic Pathology, 10th ed., Ch 14 — Red Cell Disorders (textbook)
- Harsh Mohan Textbook of Pathology, 7th ed., Ch 12 — Nutritional & Megaloblastic Anaemias (textbook)
- Devlin Biochemistry with Clinical Correlations, 8th ed., Ch 25 — B Vitamins (textbook)
Version 2.0 | NMC CBUC 2024