Vitamin B12 Deficiency

Question 1

Definition

Answer 1

Having insufficient vitamin B12 to meet demands.

Question 2

Aetiology

Answer 2

• B12 is found in meat and animal protein foods
• Absorption occurs in the terminal ileum and requires intrinsic factor (produced by
gastric parietal cells)

Question 3

Epidemiology

Answer 3

• Peak age = 60 yrs

* Vegans have a higher risk of dietary vitamin B12 deficiency

Question 4

Presenting symptoms

Answer 4

• Typical anaemia symptoms
• Fatigue
• Lethargy
• Dyspnoea
• Faintness
• Palpitations
• Headache

• Neurological Symptoms
o Paraesthesia
o Numbness
o Cognitive changes
o Visual disturbances

Question 5

Signs on physical examination

Answer 5

• Pallor
• Heart failure (can occur with severe anaemia)
• Glossitis
• Angular stomatitis
• Neuropsychiatric: irritability, dementia, depression

• Neurological
o Subacute combined degeneration of the spinal cord
o Peripheral neuropathy

Question 6

Investigations

Answer 6

• There is NO gold standard for diagnosing vitamin B12 deficiency
• Measurement of serum B12 is not very accurate or reliable
• Other new tests: plasma total homocysteine, plasma methylmalonic acid,
holotranscobalamin

• FBC and blood film
o Hypersegmented neutrophils
o Oval macrocytes
o Circulating megaloblasts

• Pernicious Anaemia Tests
o Anti-intrinsic factor antibodies
o Anti-parietal cell antibodies
o Schilling test

Question 7

Aetiology (pernicious anaemia)

Answer 7

• Pernicious anaemia is an autoimmune condition involving gastritis, atrophy of all layers of the body and fundus of the stomach and loss of normal gastric glands, parietal and chief cells
• Pernicious anaemia leads to a lack of intrinsic factor
• Pernicious anaemia accounts for 80% of megaloblastic anaemia due to impaired vitamin B12 absorption

Question 8

Aetiology (other causes)

Answer 8

• Other causes of B12 deficiency:
o Gastric - gastrectomy, atrophic gastritis
o Inadequate intake (e.g. vegan)
o Intestinal - malabsorption, ileal resection, Crohn’s affecting the terminal ileum,
tropical sprue
o Drugs - colchicine, metformin