Detection of Hb H disease caused by a novel mutation and -- SEA deletion using capillary electrophoresis.

Background Hb H disease is a serious type of alpha-thalassemia which cause moderate anemia while misdiagnosis by routine genetic analysis in a rare or novel Hb H disease. Methods The study was done on three patients and one fetus in a suspected Hb H disease family. Hb analysis was carried out using capillary electrophoresis (CE), and hematological analysis was conducted with an automated cell counter. Common alpha- and beta-thalassemia mutations were detected by routine genetic analysis (gap-PCR and RDB-PCR). Novel mutation diagnostic methods were based on DNA sequencing. Results Capillary electrophoresis revealed clinical feature of classic Hb H disease in the proband, and hematology analysis showed moderate anemia (Hb 87 g/L). But routine genetic analysis was found that it was only a heterozygote for the --(SEA) deletion. DNA sequencing of alpha-globin genes (alpha 1 and alpha 2) identified the breakpoints between nts 34162 and 34171 at alpha 2 gene, named CD 90-93 (-AGCTTCGG) mutation. The genotype of proband and fetus was the same --(SEA)/-alpha(CD90-93). His father was homozygous for the novel mutation (-alpha(CD90-93)/-alpha(CD90-93)), and his mother was heterozygote for the --(SEA) deletion. Conclusions Our study for the first time described the novel mutation CD 90-93 (-AGCTTCGG). CE is a way to avoid misdiagnosis of rare or novel Hb H disease.