[Family Study and Blood Transfusion of a Patient with Hereditary Coagulation Factor XI Deficiency]

To investigate a family with hereditary coagulation factor XI (FXI) deficiency, identify its possible genetic etiology, analyze the bleeding risk of the proband, and provide a blood transfusion regimen.

The blood samples from the family members were collected, and the coagulation parameters of the proband and her family members were detected. Whole-exome sequencing was performed on the blood samples of the proband to identify gene variants, and validate the variants in the family using Sanger sequencing. Bioinformatics softwares were used to analyze the conservation of amino acid variant sites and the impact of the variations on protein function. The pathogenicity of the variant sites was analyzed according to the genetic variation classification criteria and guidelines of the American College of Medical Genetics and Genomics (ACMG). Thromboelastography (TEG) was used to assess the coagulation function of the family members and evaluate the transfusion regimen and its efficacy in the proband.

The activated partial thromboplastin time (APTT) of the proband was significantly prolonged to 96.7 seconds, and FXI activity (FXI: C) and FXI antigen (FXI: Ag) decreased to 1.3% and 1%, respectively, both of which were extremely reduced. The FXI: C of the proband's father was also significantly lower than the normal value. The TEG results showed that the coagulation function of the proband was reduced, while the coagulation function of other family members was normal. The F11 gene of the proband exhibited compound heterozygous variants of c.738G>A (p.Trp246 *) and c.1288G>A (p.Ala430Thr). The proband's father carried a heterozygous missense variant of c.1288G>A (p.Ala430Thr), while her mother, her eldest daughter, and her youngest daughter carried a heterozygous nonsense variant of c.738G>A (p.Trp246 *). According to the ACMG genetic variation classification criteria and guidelines, c.738G>A (p.Trp246 *) is classified as a pathogenic variant (PVS1+PS3-Moderate+PP4), and c.1288G>A (p.Ala430Thr) is classified as a possible pathogenic variant (PS3-Moderate+PM1+PM3_Srong+PP4). p.Trp246 and p.Ala430 are highly conserved across different species. Swiss PdbViewer software analysis showed that p.Ala430Thr variant caused a change in the number of hydrogen bonds in FXI protein, affecting protein function. The following transfusion regimen was determined through TEG evaluation in vitro: 600 ml of fresh frozen plasma (FFP) was administered 24 hours before surgery to prevent bleeding. And there was no significant bleeding during or after the surgery.

The heterozygous nonsense variant ofc.738G>A (p.Trp246 *) and the heterozygous missense variant of c.1288G>A (p.Ala430Thr) in the F11 gene are the pathogenic factors of this hereditary FXI deficiency family.