Gene abnormalities of thalassemia syndromes in Japan

Japanese individuals with thalassemia (thal) are mostly heterozygous and asymptomatic except for microcytosis. The frequency of β-thal in Japan is one in 700-1000, and that of α-thal appears to be one-fifth of β-thal. Mutations for β-thal is heterogenous, with 8 types of mutation comprising almost 80% of all Japanese β-thalassemiacs. About 40% of the mutations seem to have been contacted from abroad. Twenty homozygotes from more than 280 thalassemiacs have been found. Eighteen homozygotes have A-G mutation at the second base of TATA box (-31 A-G) bringing about relatively mild phenotype (β^+). The -31 A-G mutation is most frequent of all Japanese β-thal's. Six rare mutations, despite being heterozygote, showed hemolytic anemia which is also called, ”dominant-type thalassemia”, and some of them demonstrated Heinz bodies in the red blood cells. The microcytosis which is characteristic of all thal, is well compensated for by an increased number of red blood cells. However, dominant-type and homozygotes for β-thal have not been compensated, resulting in anemia. The initiation codon mutations, in particular, have revealed remarkable erythremia. More than half of the α^0-thal found in the Japanese have been of the Southeast Asian type (--SEA), followed by the Filipino type (--FIL). The precise breakpoints for nearly 40% of the α^0-thal mutations remain undetermined. However, rough estimation has suggested heterogenous deletions. The α^+ thal chromosomes which are the base for emerging HbH disease, have been found in 0.25-1.55% of general population.

溶血性貧血

αサラセミア

βサラセミア

ドミナント型サラセミア

不安定血色色素症

変異

本文データは山口大学医学会の許諾に基づきCiNiiから複製したものである