Deficiency of folate causes a megaloblastic anaemia due to abnormal DNA synthesis.
Folic acid is the precursor to the folates, which are involved in the synthesis of DNA (see Fig. 12.4). Causes of folic acid deficiency:
· Low intake is most common in elderly, people living in poor social conditions and chronic alcoholics. Folic acid is found in fresh vegetables and meat, but may be destoyed by overcooking.
· Malapsorption occurs due to small bowel disease (especially if affecting the jejunum) such as coeliac disease.
· Increased requirements occur in haemolytic conditions, myeloproliferative disorders, other rapidly growing tumours and severe inflammatory disease. In pregnancy there are increased requirements and deficiency is associated with neural tube defects in the fetus.
· Antifolate drugs include methotrexate, trimethoprim, anticonvulsants and alcohol.
Symptoms and signs of anaemia. Patients may also complain of a sore mouth and tongue (glossitis).
Red cell folate level are low. In many cases the cause is not obvious and further investigations may have to be undertaken including barium follow through or upper gastrointestinal endoscopy and biopsy.
The underlying cause should be identified and treated where possible. Prior to treatment with oral folic acid supplements, concurrent vitamin B12 deficiency must be identified and treated to avoid the neurological complications of B12 deficiency. Prophylaxis is advised in pregnancy, haemolytic anaemias, premature babies, dialysis patients and those taking methotrexate.