[Analysis of a consanguineous pedigree affected with hereditary coagulation factor XII deficiency caused by homozygous Gly341Arg mutation].

OBJECTIVE To analyze the laboratory phenotype and FXII gene mutation in a consanguineous Chinese pedigree affected with factor XII (FXII) deficiency. METHODS Activated partial thromboplastin time (APTT), FXII activity (FXII:C) and FXII antigen (FXII:Ag) of the proband and her family members (10 individuals from 3 generations) were determined. Sanger sequencing was used to detect potential mutation within the 14 exons, their flanking regions and 5',3'-untranslated regions of the FXII gene. Suspected mutations were verified by backward sequencing. Conservation of the amino acids were analyzed with ClustalX-2.1-win. Four online bioinformatics software (PolyPhen-2, PROVEAN, SIFT and MutationTaster) were used to assess the impact of the mutations on the protein function. RESULTS The APTT of the proband and her elder brother have prolonged to 61.6 s and 68.6 s,and their FXII:C and FXII:Ag have decreased to 12%, 10% and 11%, 10%, respectively. The APTT of the paternal grandmother, maternal grandmother, father, mother, elder paternal aunt and elder maternal aunt were all normal, but their FXII:C and FXII:Ag have reduced to half of the normal value. Gene sequencing found that the proband and her elder brother have both carried a homozygous missense c.1078G>A (p.Gly341Arg) mutation in exon 10 of the FXII gene, for which the paternal grandmother, maternal grandmother, father, mother, elder paternal aunt and elder maternal aunt were heterozygous. Bioinformatic analysis suggested that the Gly341 is highly conserved, while p.Gly341Arg is a harmful mutation which may cause disease by affecting the function of FXII protein. CONCLUSION Homozygous p.Gly341Arg mutation, caused by consanguineous marriage, probably underlies the congenital FXII deficiency in this pedigree.