OBJECTIVETo raise awareness of the pathogenesis and diagnosis of thalassemia by reporting one case of α thalassemia patient with a large deletion fragment and analyzing the pedigree.

METHODSFirstly, blood cells and hemoglobin electrophoresis analysis were used for screening of thalassemia, and then three common kinds of deletional α thalassemia in Chinese was detected by Gap-PCR, three common kinds of non- deletional α thalassemia and seventeen common mutations of β thalassemia in Chinese were analyzed by using PCR- RDB. The unknown mutation of samples was identified with Multiplex Ligation-dependent Probe Amplification (MLPA) and DNA sequencing.

RESULTSThe proband female presented with microcytic hypochromic anemia(hemoglobin 71 g/L, mean corpuscular volume 52.4 fl, mean corpuscular hemoglobin 16.1 pg), and hemoglobin A2 1.4%. The identified large deletion fragment length was 21 925 bp, so far which had not been reported in the world and was named -α²¹·⁹. It was registered in USA DNA database and GenBank accession number as KF360979. The genotype of her mother and father and brother were αα/-α²¹·⁹, --(SEA)/-α³·⁷, αα/-α³·⁷ respectively, and the genotype of her and her sister were the same of --(SEA)/-α²¹·⁹. Her husband gene of thalassemia had no mutation, so prenatal diagnosis of thalassemia was not carried out in the pregnant woman.

CONCLUSIONThe discovery of -α(21.9) deletion mutation was enriched the DNA mutation gene database of thalassemia, and had important significance for genetic counseling and thalassemia prenatal diagnosis.