Summary

• Classically presents as megaloblastic anaemia, with absence of neurological signs.
• Common causes include dietary deficiency, malabsorption, drugs and toxins, and states of increased demand. Hereditary folate malabsorption and other inborn errors of folate metabolism are rare causes.
• In early disease, haemoglobin and MCV are normal. In severe disease, patients present with symptomatic anaemia and pancytopenia.
• Known association with fetal neural tube defects. Probable link to atherosclerosis and venous thrombosis, dementia, and colon cancer.
• Diagnosis is confirmed by the presence of low serum folate. Low RBC folate and elevated plasma homocysteine levels are helpful in situations of diagnostic difficulty.
• Cobalamin deficiency must be ruled out before initiating folic acid therapy, as the therapy may aggravate neurological manifestations of underlying vitamin B12 deficiency.
• Oral folic acid is usually considered sufficient therapy. Underlying cause should be identified and treated.
• Food fortification programmes have been instituted in some countries to decrease the incidence of folate deficiency and its disease associations.