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.</p
