RESUMO
<p><b>OBJECTIVES</b>To identify the FXI gene mutations in two Chinese pedigrees of congenital factor XI deficiency.</p><p><b>METHODS</b>The peripheral blood samples were collected from the probands and their family members and the plasma FXI:C and FXI:Ag were determined. All the exons and exon-intron boundries of FXI gene were amplified with PCR and sequenced thereafter.</p><p><b>RESULTS</b>A nonsense mutation Trp228stop and two missense mutations Glu323Lys and Leu172Pro were disclosed in the two pedigrees. All mutations existed in a heterozygous state.</p><p><b>CONCLUSION</b>The FXI gene mutations Trp228stop, Glu323Lys and Leu172Pro attribute to the pathogenesis of the congenital factor XI deficiency in Chinese. The Leu172Pro is identified for the first time.</p>