About

Pernicious anaemia is an autoimmune disorder affecting the gastric mucosa that results in vitamin B12 deficiency. It is helpful to remember that pernicious means 'causing harm, especially in a gradual or subtle way' - the symptoms of signs are often subtle and diagnosis is often delayed.

Whilst pernicious anaemia is the most common cause of vitamin B12 deficiency, it's not the only cause. Other causes include atrophic gastritis (e.g. secondary to H. pylori infection), gastrectomy, malnutrition (e.g. alcoholism).

Pathophysiology

• antibodies to intrinsic factor +/- gastric parietal cells

  • intrinsic factor antibodies → bind to intrinsic factor blocking the vitamin B12 binding site
  • gastric parietal cell antibodies → reduced acid production and atrophic gastritis. Reduced intrinsic factor production → reduced vitamin B12 absorption

• vitamin B12 is important in both the production of blood cells and the myelination of nerves → megaloblastic anaemia and neuropathy

  vitamin b12 is used in the body to regenerate foic acid - which eventually produces haem

Risk factors

• more common in females (F:M = 1.6:1) and typically develops in middle to old age
• associated with other autoimmune disorders: thyroid disease (50% of patients with PA have thyroid antibodies), type 1 diabetes mellitus, Addison's, rheumatoid and vitiligo
• more common if blood group A

PC/Features:

• anaemia features
  • lethargy
  • pallor
  • dyspnoea
• neurological features
  • peripheral neuropathy: 'pins and needles', numbness. Typically symmetrical and affects the legs more than the arms
  • subacute combined degeneration of the spinal cord: progressive weakness, ataxia and paresthesias that may progress to spasticity and paraplegia
  • neuropsychiatric features: memory loss, poor concentration, confusion, depression, irritabiltiy
• other features
  • mild jaundice: combined with pallor results in a 'lemon tinge'
  • glossitis → sore tongue

Investigation