[The inherited coagulation factor XI deficiency caused by intronic mutation IVS J-4delgttg].

To identify gene defect in a Chinese pedigree of hereditary coagulation factor XI (FXI) deficiency.The peripheral blood samples were collected from the proband and her family members. The plasma PT, APTT, FXI:C and FXI:Ag were assayed. The FXI gene exons and exon-intron boundaries of the proband were amplified by PCR and then sequenced directly. The mRNA of FXI in the peripheral blood was analyzed with RT-PCR.The proband and some of her family members had prolonged APTT. The plasma FXI:C and FXI:Ag of the proband, her brother and her parents were lower than 10% and 50% of the normal values, respectively. Nucleotide sequence analysis revealed that the proband and her brother had a homozygous mutation of IVS J-4delgttg in FXI gene. The mutation was inherited from her parents who were heterozygotes. The mutation was not found in 60 normal subjects. No FXI mRNA was detected in peripheral blood sample of the proband.The IVS J-4delgttg is a novel mutation causing FXI deficiency, which may interfere with mRNA splicing.