Characterization of congenital factor XII deficiency in Taiwanese patients: identification of one novel and one common mutation

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.