Megaloblastic anemia in Japan.

Since 1903, 744 cases of megaloblastic anemia have been reported in Japan: 490 cases of pernicious anemia; 95 cases associated with pregnancy; 66 cases after gastrectomy; 22 cases of megaloblastic anemia of infants; 21 cases of folic acid deficiency other than pregnancy and 19 cases of vitamin B12 malabsorption after ileal resection. It is generally agreed among hematologists in Japan that pernicious anemia is relatively rare, as in other Asian countries. The diagnosis of pernicious anemia in Japan is usually made by stained marrow films, radioisotopic assay of serum vitamin B12, Schilling test and good response to vitamin B12 therapy. Serum folate level, intrinsic factor or its antibody, methylmalonic acid excretion, formiminoglutamic acid excretion and deoxyuridine suppression test are performed only at a small number of laboratories. The drugs of choice are hydroxocobalamin, deoxyadenosylcobalamin and methylcobalamin. Cyanocobalamin has nearly disappeared from commercial sources in Japan. Vitamin B12 administration is common in patients with neurological disorders. Megaloblastic anemia due to folic acid deficiency is extremely rare in Japan. Low serum folate levels are frequently observed among patients receiving anticonvulsants or in pregnant women, but in such samples megaloblastic anemia is almost never detected. The folic acid content of hospital diets indicates that satisfactory amounts of folate are taken in Japan. The intake of folic acid from rice is well over the minimum daily requirement of folate. Other factors in folic acid deficiency, such as food taboos, severe alcoholism and malabsorption syndrome are not frequently found in Japanese. The inadequate intake of folate was the critical factor in most reported cases.