Abstract
We present two Japanese students with thalassemia identified during screening for anemia in their junior high school. Blood test results revealed marked hypochromic and microcytic erythrocytosis in one patient and microcytic anemia in the other. Both cases showed a mean corpuscular volume/red blood cell (MCV/RBC) ratio less than 13. Their β/α synthesis ratio was elevated. Deletion of ψα2, ψα1, α2, α1 and &thetas;1 genes in the α-globin gene clusters were noted in the first case. This pattern of gene deletion was consistent with heterozygous α-thalassemia 1 of the Southeast Asian type. On the other hand, an increased hemoglobin A2 level and reduced β/α synthesis ratio were found in the second case. Direct cloning and DNA sequencing identified a point mutation (guanine to adenine) at position 1 of intervening sequence II in the β-globin gene (IVS II-1 G→A). These results suggest that this patient had heterozygous β0-thalassemia. Diagnosis of thalassemia should be confirmed by molecular analysis in cases with microcytic anemia or hypochromic microcytosis with a MCV/RBC ratio of 13 or less.
