Vitamin B12 and folate deficiency

Question 1

Define

Answer 1

DEFINITION: having insufficient vitamin B12 to meet demands.

Question 2

Causes

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)

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

Other causes of B12 deficiency:

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

Question 3

Epidemiology

Answer 3

Peak age = 60 yrs

Vegans have a higher risk of dietary vitamin B12 deficiency

Question 4

Symptoms

Answer 4

Typical anaemia symptoms

Fatigue

Lethargy

Dyspnoea

Faintness

Palpitations

Headache

Neurological Symptoms

• Paraesthesia
• Numbness
• Cognitive changes
• Visual disturbances

Question 5

Signs

Answer 5

Pallor

Heart failure (can occur with severe anaemia)

Glossitis

Angular stomatitis

Neuropsychiatric: irritability, dementia, depression

Neurological

• Subacute combined degeneration of the spinal cord
• 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

• Hypersegmented neutrophils
• Oval macrocytes
• Circulating megaloblasts

Pernicious Anaemia Tests

• Anti-intrinsic factor antibodies
• Anti-parietal cell antibodies
• Schilling test