[Analysis of two consanguineous Chinese pedigrees affected with Hereditary prokallikrein deficiency and High molecular weight kininogen deficiency].

Objective: To analyze the laboratory phenotype and genetic variants of two consanguineous Chinese pedigrees affected with Hereditary prokallikrein (PK) and High molecular weight kininogen (HMWK) deficiency and explore their molecular pathogenesis.

Methods: A PK deficiency pedigree (10 individuals from 4 generations) and a HMWK deficiency pedigree (6 individuals from 3 generations) which were admitted to the First Affiliated Hospital of Wenzhou Medical University on December 3, 2021 and June 16, 2022, respectively were selected as the study subjects. Clinical data of the two pedigrees were collected, and the related coagulation indexes of the probands and their family members were determined. Genomic DNA of the two pedigrees was extracted from peripheral blood samples. All of the exons and flanking sequences of the KLKB1 and KNG1 genes of the probands were analyzed by direct sequencing. And the corresponding sites were sequenced among other family members. Bioinformatic software was used to analyze the conservation of variation sites and the effect of variant on the protein function.

Results: The plasma PK activity of proband 1, a 29-year-old female, and her brother were extremely low (< 1.0%). Proband 2 was a 66-year-old male with extremely low plasma HMWK activity (< 1.0%). Genetic sequencing revealed that the proband 1 and her brother had both harbored a homozygous c.417_418insCATTCTTA (p.Arg140Hisfs*3) insertional variant in exon 5 of the KLKB1 gene. Proband 2 had harbored a homozygous c.460C>A (p.Pro154Thr) missense variant in exon 4 of the KNG1 gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variants were respectively rated as pathogenic (PVS1+PM2_Supporting+PM4) and likely pathogenic (PS4+PM2_Supporting+PP3+PP4).

Conclusion: The c.417_418insCATTCTTA (p.Arg140Hisfs*3) variant of the KLKB1 gene and the c.460C>A (p.Pro154Thr) variant of the KNG1 gene probably underlay the decreased PK and HMWK activities in the two pedigrees, respectively.