Mariam Swidan: Vitamin B12 Deficiency and the Hidden Risk of Neurological Damage
Mariam Swidan, Biomedical Science Graduate, Clinical Laboratory Professional, shared a post on LinkedIn:
”Disease Overview 12 – Vitamin B12 Deficiency
Sometimes anemia isn’t the disease – it’s the warning sign.
Vitamin B12 is essential for DNA synthesis and cell division. When it is deficient, nuclear maturation is delayed while cytoplasmic development continues, resulting in megaloblastic changes.
This process affects more than red blood cells. All rapidly dividing cells, including white blood cells and platelets, are also impacted.
Key consequences:
- Ineffective erythropoiesis leading to anemia
- Macrocytosis (increased MCV)
- Hypersegmented neutrophils
- Possible pancytopenia in severe cases
- Vitamin B12 deficiency also has important neurological consequences because it is essential for myelin synthesis.
Myelin is the fatty insulating sheath that surrounds and protects nerve axons.
Neurological manifestations:
- Loss of proprioception, causing difficulty sensing limb position and movement
- Neuropsychiatric symptoms (‘B12 psychosis’), including hallucinations, paranoia, or mania in severe deficiency
- Subacute combined degeneration of the spinal cord, which may progress to irreversible neurological disability if untreated
Common causes:
- Poor dietary intake (e.g., strict vegan diet)
- Malabsorption due to intrinsic factor deficiency
- Gastrointestinal disorders affecting vitamin B12 absorption
Clinical pearl:
The complete blood count and peripheral blood smear often provide the first clues to vitamin B12 deficiency—sometimes even before serum vitamin B12 levels are measured.”

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