Megaloblastic anaemia is a major type of anaemia (a reduced level of the oxygen-carrying pigment haemoglobin in the blood). Megaloblastic anaemia is caused by deficiency of vitamin B12 or another vitamin, folic acid. Either of these deficiencies seriously interferes with the production of red blood cells in the bone marrow. An excess of cells known as megaloblasts (abnormal immature red cells) appears in the marrow. Megaloblasts give rise to enlarged and deformed red blood cells known as macrocytes.

MEGALOBLASTIC ANAEMIA CAUSES

Vitamin B12 deficiency

Vitamin B12 is found only in foods of animal origin, such as meat and dairy products. It is absorbed from the small intestine by first combining with intrinsic factor, a chemical produced by the stomach lining. The most common cause of vitamin B12 deficiency is pernicious anaemia in which the stomach lining fails to produce intrinsic factor, usually as a result of an autoimmune disorder (in which the immune system attacks the body’s own tissues). Total gastrectony (removal of the stomach) also prevents the production of intrinsic factor, and removal of part of the small intestine prevents B12 absorption, as does the intestinal disorder Crohn’s disease. In a minority of cases, vitamin B12 deficiency is due to a vegan diet (which excludes all foods of animal origin).

Folic acid deficiency

Folic acid is found mainly in green vegetables and liver. The usual cause of folic acid deficiency is a poor diet. It can also be caused by anything that interferes with absorption of folic acid from the small intestine (Crohn’s dosease or coeliac disease, for example). Folic acid is required by rapidly dividing cells, as in the fetus. Women are advised to take the recommended dose of folic acid supplements before conception and in early pregnancy, although this is to reduce the risk of the fetus having a neural tube defect rather than to prevent anaemia.

MEGALOBLASTIC ANAEMIA SYMPTOMS

Many people with mild megaloblastic anaemia have no symptoms. Others may experience tiredness, a sore mouth and tongue, weight loss, and mild jaundice. If B12 deficiency continues for a long time, additional symptoms as a result of nerve damage, including numbness and tingling in the feet, may develop.

MEGALOBLASTIC ANAEMIA DIAGNOSIS AND TREATMENT

Megaloblastic anaemia is diagnosed by blood tests and confirmed if a bone marrow biopsy (removal of a sample of marrow for microscopic analysis) reveals the presence of numerous megaloblasts. Megaloblastic anaemia caused by poor diet can be remedied by a short of vitamin B12 injections or folic acid tablets and the introduction of a normal diet. A lifelong course of vitamin b12 injections or folic acid tablets is required if the underlying cause of malabsorption is incurable.

Source: A-Z family medical encyclopedia by BMA

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