Characterization of hereditary factor XI deficiency in Taiwanese patients: identification of three novel and two common mutations

Hereditary coagulation factor XI (FXI) deficiency is a rare bleeding disorder, but information on FXI deficiency in Taiwanese patients remains scarce. We evaluated clinical and genetic features of severe FXI deficiency patients in Taiwan. We collected clinical information and performed coagulation laboratory tests and genetic studies in ten unrelated Taiwanese families with severe FXI deficiency. FXI coagulation activity was assayed using a one-stage method. FXI antigen was determined using enzyme-linked immunosorbent assay. Underlying genetic mutations were evaluated using direct sequencing methods. Ten unrelated Taiwanese patients with hereditary FXI deficiency and variable bleeding tendencies were analyzed. Half of the patients were male. The most common bleeding manifestations were easy bruising (40%), bleeding after dental procedures (40%), and postoperative bleeding (33%). Two patients (20%) were asymptomatic. No correlation was found between bleeding manifestations and baseline FXI levels. Three novel mutations were identified: c.1322delT p.Lys442Cysfs*8, c.599G > C p.Cys200Ser, and IVS4 c.325 + 2del124. Two common mutations, c.1107C > T p.Tyr369* (40%) and c.841C > T p.Gln281* (30%), were also found. No correlation existed between bleeding and FXI activity, highlighting the difficulty in predicting FXI deficiency-related bleeding. Three novel FXI genetic mutations and two common mutations were identified, contributing to the known spectrum of FXI deficiency-related mutations. ? 2020, Japanese Society of Hematology.