[Hemoglobinopathies in Japan: characteristics and comparison with those of other ethnic groups]

Abnormalities of hemoglobin (Hb), or hemoglobinopathies, are classified into Hb abnormalities that arise from altered quality induced mainly by amino acid substitution. Furthermore, thalassemia is a quantitative abnormality of normal Hb. Most hemoglobinopathies are inherited disorders. The abnormal Hb known to date comprise more than 210 types in the Japanese population. The rate of thalassemia in Japan is less than that in endemic regions, but the frequencies of β- and α- thalassemias are 1/1,000 and 1/3,500 in the general population, respectively, so not particularly rare. The mutation spectrum is different from that of endemic regions, probably because Japanese have been historically isolated islanders. Japanese hemoglobinopathy generally has minor symptoms, which are different from those in endemic areas where thalassemia exhibits major clinical manifestations. This might be why useful knowledge is obtained in our laboratory which concentrates on detailed observation of clinical data in addition to genetic analysis. We have, in fact, discovered new clinical characteristics and the significance of hemoglobinopathy, especially of minor or intermediate thalassemia. This approach is quite different from that in other countries coping with only the major type. By focusing on this novel approach, we aim to contribute to improving diagnostic technology for patients.