in aids , as previously found in pernicious anemia ( pa ) , the earliest serum marker of subnormal vitamin b12 ( cobalamin ) absorption , and therefore of negative b12 balance , is low serum holotranscobalamin ii ( holo-tc ii ; b12-tc ii ) despite normal total serum b12 level , normal serum homocysteine , and normal classic ( oral free radio-b12 ) schilling test .
C0002892
pernicious anemia
C0042845
cobalamin