Pernicious anaemia (PA) is a disease of the stomach that is characterised by megaloblastic anaemia due to vitamin B12 deficiency, itself, secondary to intrinsic factor deficiency and gastric atrophy. It usually has an autoimmune basis.
PA primarily affects the elderly - most patients are over 60 years of age; less than 10% of cases are under 40 years of age; it is rare in children. Women are affected more often than men, in a ratio of 3:2.
It occurs more commonly than by chance in first degree relatives, in those with blood group A and in those with fair or prematurely grey hair and blue eyes. It may be associated with autoimmune diseases, such as Addison's disease, and also with an increased risk of gastric carcinoma.
Treatment is aimed at correcting the vitamin B12 deficiency.