MEGALOBLASTIC ANAEMIA

B12 deficiency (40%)

inadequate dietary intake (strict vegans)

malabsorption:

gastric:

pernicious anaemia [commonest cause]

congenital deficiency of intrinsic factor

intestinal:

disease of terminal ileum, eg. Crohn's disease, ileal resection, tropical sprue, tuberculosis

loss of B12:

parasites, eg. fish tapeworm

blind loop syndrome [bacterial overgrowth], eg. jejunal diverticulum, ileocolic fistula

metformin

congenital specific malabsorption with proteinuria (Imerslund-Gräsbeck syndrome)

congenital defects of B12 metabolism (rare)

prolonged N2O anaesthesia (interferes with B12 metabolism)

folate deficiency (60%)

inadequate diet [fresh vegetables and meat]

methotrexate

rarely trimethoprim, pyrimethamine

coeliac disease

congenital defect

increased body demands (rapid cell turnover; normal dietary intake not enough):

leukaemias (especially during treatment)

chronic inflammation, eg. rheumatoid arthritis, Crohn's disease, extensive psoriasis

treatment of any malignancy with radiotherapy or chemotherapy

dialysis

congestive heart failure

congenital defects of folate metabolism (rare)

liver disease

barbiturates, eg. primidone