New Compound Heterozygous Mutations of GPIIb in Patient with Glanzmann Thrombasthenia.

Glanzmann thrombasthenia (GT) is a homozygous or compound heterozygous autosomal recessive bleeding disorder caused by the qualitative or quantitative deficiency of integrin GPIIb-IIIa, which acts as the receptor of platelet fibrinogen. Here we report a case of GT with a compound heterozygous mutation in GPIIb according to the results of flow cytometry and genetic investigation.The flow cytometry was used to measure the average amounts of integrin GPIIb-IIIa on the patient’s platelets, and all 30 exons of GPIIb were amplified and sequenced with the corresponding primers.The average fluorescence intensity of integrin GPIIb-IIIa were 3.07 and 12.5, respectively, compared with 23.7 and 254, respectively, in the normal healthy individuals. And sequencing analysis of all exons of GPIIb demonstrated that there existed following compound heterozygous mutations in GPIIb gene: one heterozygote mutation (68 C→A) in the 1^st exon, which resulted in Pro 23 His substitution in signal peptide domain; one nonsense heterozygous mutation (1750 C→T) in the 17^th exon, which result in premature termination; one heterozygote mutation (2159 T→C) in the 21^stexon, which resulted in Leu 720 Pro substitution. According to Glanzmann thrombasthenia database of ISTH (http://sinaicentral.mssm.edu/intranet/research/glanzmann/listmutations?mut=GPIIb), 68 C→A mutation and 2159 T→C mutation are novel mutations in the GPIIb heavy chain. These compound heterozygous mutations in GPIIb gene might be a novel pathogenetic mechanism of GT, which impaired the protein translation and co-expression with GPIIIa on the membrane of platelet.