RESUMEN
RATIONALE: Factor X (FX) deficiency is a rare autosomal recessive bleeding disorder. The majority of patients carry a missense mutation in F10, and patients with bleeding disorders are either homozygous or compound heterozygous for F10. Nonsense mutations are exceptionally rare, and a heterozygous nonsense mutation is not considered to cause bleeding disorders. PATIENT CONCERNS: A 35-year-old Japanese female with an incidental hemorrhage after gynecologic polypectomy was referred to our hospital. DIAGNOSES: Following differential diagnostic workup, including cross-mixing test, congenital FX deficiency was strongly suspected. INTERVENTION: Coagulation tests and mutation analyses were conducted for the patient and her parents. OUTCOMES: Mutation analysis revealed that she carried a heterozygous nonsense mutation in F10. Pedigree analysis revealed that the mutation was inherited from her mother although there was no familial history of bleeding or hemostatic disturbance. LESSONS: Hemostatic disturbance may occur even in a patient with heterozygous F10. Because heterozygous nonsense mutation in F10 is expected to be hidden in an apparently healthy population, as observed in our patient, unexpected hemostatic disturbance may occur, particularly during the use of direct oral anticoagulant (DOAC)-targeting factor Xa for thrombotic diseases. FX activity should be evaluated before prescribing DOACs to patients.