Pernicious anaemia

This is a vitamin B12 deficiency disease.

 

Physiology

• Intrinsic factor (IF or GIF) is secreted by gastric parietal cells in fundus of the stomach. 
• GIF binds to vitamin B12 and forms a GIF-B12 complex. 
• The GIF-B12 complex bind to receptors on enterocytes along the ileum of the small intestine. 
• The complex is absorbed into the enterocytes and dissociates into GIF and vitamin B12.

 

Pathophysiology

In most cases of pernicious anaemia:

• There is autoimmune mediated destruction of gastric parietal cells. 
• With a lack of gastric parietal cells, there is deficient synthesis and secretion of GIF.
• With deficient GIF , there is deficient Vitamin B12 absorption in the small intestine.

Some cases of pernicious anaemia involve genetic disorders, e.g. defective enterocyte receptors.

 

Symptoms

• Fatigue
• Weakness
• Dyspnoea
• Palpitations

 

Signs

• Pallor 
• Tachycardia

 

Consequences

• Vitamin B12 deficiency anaemia
• Subacute Combined Degeneration

 

Investigations

• Full blood count : macrocytic, megaloblastic anaemia
• Intrinsic Factor antibody : positive

 

Management

Dietary supplementation of Vitamin B12 cannot correct the nutritional deficiency because the B12 will not be absorbed sufficiently in the small intestine.

• Parenteral Vitamin B12 supplementation (injections)