A Rare Case Report of Acquired Coagulation Factor XI Deficiency.

Background: Acquired coagulation factor deficiency is an autoimmune hemorrhagic disease caused by the production of antibodies to coagulation factor. The incidence of acquired coagulation factor XI deficiency is low and rarely reported.

Case presentation: We report a case of a patient with acquired coagulation factor XI deficiency. The patient was a 24-year-old female who presented with mild yellowing of the skin, general malaise, palpitation, and no obvious bleeding symptoms prior to admission, such as skin and mucous membrane petechiae. She was initially diagnosed with anemia because her hemoglobin was 62 g/L. Laboratory results showed activated partial thromboplastin time (APTT) prolonged with a test value of 83.40 seconds and could not be corrected by corrective experiments; Factor XI activity was less than 0.1%, positive for factor XI antibody, and a plasma coagulation factor XI inhibitor was 35.20 BU/mL. She was eventually diagnosed with acquired coagulation factor XI deficiency, Plasmapheresis were performed to clear antibodies, and patient's condition improved.

Conclusions: Plasmapheresis played a positive role in the treatment of acquired factor XI deficiency. Clear early diagnosis and proper treatment can help to improve the cure rate of patients.