[Beta(+)-thalassemia (-31CapA-->G) homozygosity discovered on the mass medical examination: diagnosis for beta-thalassemia and DNA analysis].

A 44-year-old Japanese male showed a high value of HbF (14.3%) in an assay of glycated Hb (HbA1c) by use of HLC-723GHb II system. The proband was asymptomatic although he was found to be anemic ten years ago. The hematological examination revealed microcytosis, hypochromia and slight reticulocytosis (3.7%). Serum iron level was high (245 g/dl). Blood smear revealed aniso-poikilocytosis with scattered target cells. Hb analysis showed a remarkable increase of HbA2 (8.6%) as well as the high HbF cited above, but no abnormal Hb was detected. The beta/alpha ratio of globin biosynthesis in reticulocytes was decreased to 0.25. DNA sequencing of the beta-globin gene disclosed that the proband was homozygous for beta (+)-thalassemia mutation-31CapA-->G. This mutation was linked to A gamma T gene and haplotype -(-)+2(-)+2-. His parents and two daughters were heterozygous for the mutation. They were anemic and had increased HbA2 levels of 4.36-5.43%. The beta/alpha ratios of globin biosynthesis were 0.61-0.81.