[Urinary methylmalonic acid excretion and clinical features in megaloblastic anemia due to vitamin B12 deficiency].

Urinary methylmalonic acid (MMA) excretion in megaloblastic anemia due to vitamin B12 (B12) deficiency was studied using a colorimetric method. Average MMA excretion in 20 patients with untreated B12 deficiency was 164 mg/day, whereas it increased to 518 mg/day following oral administration of 10 g L-valine. Urinary MMA correlated significantly with platelet number, erythroblast percentage and deoxyuridine suppression test, while no correlation was found with hemoglobin, leukocyte number, reticulocyte, serum LDH, serum B12 and folate concentration. Patients with neurological disturbances excreted significantly larger amounts of MMA than those without neurological disorders. The results also indicated that MMA could be a useful adjunct for differentiation of megaloblastic anemia from myelodysplastic syndromes showing marked megaloblastic changes.