A novel homozygous frameshift mutation (p.Lys365Glnfs*69) in a family with hereditary factor XII deficiency: a case report.

Factor XII (FXII) deficiency is a rare autosomal recessive disorder characterized by prolonged activated partial thromboplastin time (APTT) without bleeding diathesis. Genetic diagnosis is critical to avoid unnecessary interventions. An 8-year-old boy with incidentally prolonged APTT (> 170 s) was referred for preoperative evaluation. FXII activity was 7.7%. No personal/family history of bleeding or thrombosis was reported. Genetic testing revealed F12: c.1092dup homozygous mutations in F12, inherited from his parents. Familial segregation confirmed autosomal recessive transmission. The identification of these mutations expands our understanding of the genetic basis of factor XII deficiency and emphasizes the importance of genetic diagnosis in such cases.