Combined Coagulation Factor XI and Factor XII Deficiencies in an Asymptomatic Black Female

Background: While there are multiple studies describing combined coagulation factor deficiencies, their genetic defects and clinical significance remain largely unknown. We present the case of an asymptomatic Black female with deficiencies of both coagulation factor XI and factor XII. To our knowledge, the combination of coagulation factor XI and XII deficiencies has not previously been reported in a Black individual.

Case Report: In April 2024, a healthy 29 year old Black female from Honduras without personal or family history of bleeding or bruising, presented with a prolonged activated partial thromboplastin time (aPTT) that was incidentally found during a routine pre-operative evaluation for elective cosmetic surgery. Her prothrombin time (PT) was normal. Her aPTT was prolonged to 43.4 seconds (reference interval 25.4 - 34.9 seconds) and normalized with 1:1 mixing studies of patient and normal plasma. She was therefore evaluated for deficiencies in factors VIII, IX, and XI, as well as for the presence of a lupus anticoagulant. Her factor VIII and IX levels were normal. No lupus anticoagulant was detected. Her factor XI levels were decreased: 47% in April 2024, 56% in June 2024, and 58% in July 2024 (reference range 60 - 150%). Her factor XII levels were also decreased at 39% in April 2024 and borderline normal at 51% in July 2024 (reference range 50 - 150%). She has no past medical history and has never had excessive bleeding. She has been pregnant once and delivered a healthy baby via an uncomplicated spontaneous vaginal delivery at full term.

Conclusion: Although detection and identification of combinations of coagulation factor deficiencies is readily available, their underlying genetic defects and clinical significance requires ongoing investigation.

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