Megaloblastic anaemia

Megaloblastic anaemia is characterized by macrocytic red cells and hypersegmented neutrophils in the peripheral blood, and by a typical appearance of the erythroblasts in the bone marrow. It is almost always caused by deficiency of cobalamin (vitamin B12), which may also cause a neuropathy, or by deficiency of folate. Pernicious anaemia, an autoimmune gastritis in which antibodies to intrinsic factor and/or parietal cells are usually present in serum and serum gastrin levels are raised, is the most frequent cause of severe cobalamin deficiency in Western countries. Other gastric or small intestinal diseases or surgical resections may also cause malabsorption of cobalamin. Vegans and strict vegetarians may become cobalamin deficient. Folate deficiency may be due to malabsorption as in coeliac disease but poor diet and excess utilization e.g. in pregnancy or haemolytic anaemias are also causes. The deficiencies are usually diagnosed by serum cobalamin and folate assays. Treatment of cobalamin deficiency is either with injections of hydroxocobalamin or daily oral cyanocobalamin. Folic acid is given orally for folate deficiency and is also used to fortify the diet in over 80 countries to reduce the incidence of newborns with neural tube defects.