Factor XII deficiency: a clinical and molecular genetic study

Rare Inherited Coagulation Deficiencies: A Single-Center Study

BACKGROUND

Rare factor deficiency (RFD) is characterized by a deficiency of factor (F)I, FII, FV, FVII, FX, FXI, FXII, FXIII, or a combined deficiency of FV+FVIII or vitamin K-dependent factors. The prevalence of RFD ranges from 1/1,000,000 to 3,000,000. Combined deficiencies of vitamin K-related factors have been described in 30 families worldwide, and these patients can present with a wide range of clinical symptoms, from mucocutaneous bleeding to life-threatening symptoms such as central nervous system and gastrointestinal bleeding.

OBJECTIVE

This study aimed to contribute to the literature on RFD.

MATERIAL AND METHODS

This retrospective study analyzed data from 43 children with RFD.

RESULTS

The most common factor deficiencies were FVII (n=13); whereas the other deficiencies were FI (n=1), FV (n=2), FV+FVIII (n=2), FX (n=6), FXI (n=5), FXII (n=9), FXIII (n=3), and vitamin K-dependent combined factor deficiency (n=2). Acute and severe bleeding was controlled by treatment in 6 patients, and 12 patients with recurrent bleeding symptoms received prophylaxis. RFDs were more common in regions with high rates of consanguineous marriage, and in our study, 16 (16/43) of the cases were found to have consanguineous marriages between parents.

CONCLUSIONS

It is important to improve genetic counseling and access to testing for family members with RFD due to autosomal recessive inheritance. Delays in diagnosis and treatment and lack of adequate prevention are important risk factors for life-threatening bleeding.

Clinical and genetic spectrum of factor XII deficiency in the Han population of East China

BACKGROUND

Factor XII (FXII or F12) deficiency is a rare inherited disorder, typically lacking haemorrhagic symptoms. There is limited literature exists on FXII deficiency and mutations within the Chinese population. This study aimed to characterize the spectrum of F12 gene mutations in a Chinese cohort and to investigate the relationship between FXII mutations and clinical phenotypes.

METHODS

Genetic and clinical data from 51 unrelated probands with FXII deficiency, along with their families, were meticulously collected and analysed.

RESULTS

Genetic analysis revealed that 94.1% of probands carried genetic defects, with 29 mutations pinpointed in the F12 gene. Of these, 18 mutations were previously reported for the first time by our research group, including c.303_304delCA, c.1078G > A, c.1285 C > T, among others. Of the mutations, 17 are missense, constituting 58.6% of the total. Additionally, 11 are deletions or insertions, of which 8 result in frameshifts, while the remaining one is a nonsense mutation. These mutations were predominantly concentrated in two crucial regions: the catalytic domain and the kringle domain. The most frequently observed mutations were c.1681G > A, closely followed by c.1561G > A and c.1078G > A, indicating a dominance among these mutations. Additionally, a prevalent polymorphism at position 46 was observed in the majority of probands, with 47.1% having the 46T/T genotype and 13.7% having the 46 C/T genotype, which may potentially impact FXII activity. The broad spectrum of asymptomatic FXII deficiency observed within the Han population of East China.

CONCLUSIONS

We speculate on the potential impact of recurrent mutations on the efficacy of new drugs being developed to target FXII for thrombosis prevention and treatment. Furthermore, it is important to explore their influence on FXII-related pathways beyond the activation of the contact pathway in the coagulation cascade.

Homozygous missense variant F12 (Gly506Asp) associated with severe factor XII deficiency: a case report

BACKGROUND

Factor XII deficiency can be related to either homozygous or compound heterozygous pathogenic variants in the F12 gene. The disease is commonly known as Hageman trait and is inherited in both autosomal recessive or dominant patterns. Clinically, factor XII deficiency is not associated with bleeding but conversely has been linked to thrombotic events, recurrent pregnancy loss, and hereditary angioedema. Molecular data of F12 deficiency are scarce and have revealed varying results between cases. However, most of the reported variants are missense mutations, gross deletions, or small insertion. Factor XII deficiency has been reported in the Saudi population in several studies, either as isolated case reports or included within the studies of rare bleeding factors deficiency. However, molecular data are lacking as no case report of genetic studies related to factor XII deficiency has been published in our local population, to the best of our knowledge.

CASE REPORT

Herein we describe a homozygous missense variant involving exon 12 within F12 gene (5:176,830,269 G>A; p.Gly506Asp) in a 36-year-old Saudi multiparous female referred from the surgical clinic with significantly high activated partial thromboplastin time during preoperative assessment for sleeve gastrectomy. The patient had no history of bleeding episodes during the previous deliveries nor any tooth extractions. She had single event of spontaneous abortion during the 15th week of gestation without any bleeding complication. There was no history of thrombosis or skin manifestations, and she was not taking any medicines. There was no family history of bleeding or thrombosis. Family history revealed consanguinity as the parents are first-degree cousins. Physical examination was unremarkable. Upon investigation, the prolonged activated partial thromboplastin time was fully corrected by a 1:1 mixing study with normal pool plasma while lupus anticoagulant tests were negative. Factor assays and von Willebrand factor tests are all within normal ranges except for factor XII, which was severely deficient. A homozygous missense variant involving exon 12 within F12 gene (5:176,830,269 G>A; p.Gly506Asp) was identified.

CONCLUSION

F12 (5:176,830,269 G>A; p.Gly506Asp) variant is likely to be a pathogenic variant among homozygous factor XII-deficient patients. Genetic counseling and management of the patients and families should be based on clinical evaluation.

Whole-exome sequencing reveals a novel frameshift mutation in a consanguineous family with a hereditary coagulation factor XII deficiency

BACKGROUND AND AIMS

We aimed to elucidate a hereditary mutation of coagulation factor XII (FXII) in a consanguineous Chinese family.

METHODS

Mutations were investigated using Sanger and whole-exome sequencing. FXII (FXII:C) activity and FXII antigen (FXII:Ag) were assessed using clotting assays and ELISA, respectively. Gene variants were annotated and the likelihood that amino acid mutations would affect protein function was predicted using bioinformatics.

RESULTS

Activated partial thromboplastin time was prolonged to >170 s (reference range, 22.3-32.5 s), and FXII:C and FXII:Ag were decreased to 0.3% and 1%, respectively, (normal range for both, 72%-150%) in the proband. Sequencing revealed a homozygous frameshift mutation c.150delC (p.Phe51Serfs*44) site in the F12 gene exon 3. This mutation results in premature termination of the encoded protein translation and the protein is truncated. Bioinformatic findings indicated a novel pathogenic frameshift mutation.

CONCLUSION

The c.150delC frameshift mutation p.Phe51Serfs*44 in the F12 gene likely explains the low FXII level and the molecular pathogenesis of an inherited FXII deficiency in a consanguineous family.