A Case Report of Coagulation Factor XII Deficiency

BACKGROUND: Coagulation factor XII (FXII) deficiency is a rare coagulation disorder, often incidentally detected during routine physical examinations, invasive procedures, or preoperative screenings, with no specific clinical manifestations. Here, we report a case of FXII deficiency. METHODS: A 46-year-old female patient was found to have unexplained prolonged activated partial thromboplastin time (APTT) during routine preoperative testing, without clinical bleeding symptoms. We performed an APTT mixing study, anti-cardiolipin antibody (ACA) testing, anti-β2-glycoprotein 1 (anti-β2-GP1) antibody testing, lupus anticoagulant (LA) screening, and coagulation factor assays to determine the cause of APTT prolongation. RESULTS: The APTT mixing study showed correction result. Coagulation factor assays revealed significantly reduced FXII activity (0.1%), while factors XI, X, II, VIII, IX, V, and VII levels were elevated. ACA (IgA/IgG/IgM) and anti-β2-GP1 antibodies (IgA/IgG/IgM) were negative. LA testing by dilute Russell's viper venom time (dRVVT) was negative, and the silica clotting time (SCT) suggested factor deficiency rather than an inhibitor. These findings confirmed that the patient's prolonged APTT was due to FXII deficiency. CONCLUSIONS: When prolonged APTT is observed in a patient without bleeding symptoms, laboratory personnel should consider the possibility of FXII deficiency.