Acquired Factor XI Inhibitor Presenting as Spontaneous Bilateral Subdural Hematoma in an Elderly Patient

Diagnosis and management of factor XI alloinhibitors in patients with congenital factor XI deficiency-A large single-centre experience

INTRODUCTION

Factor (F) XI deficiency is an inherited bleeding disorder with increased prevalence in Ashkenazi Jews where it is mainly caused by two variants, p.Glu135* (type II, leading to a null allele) and p.Phe301Leu (type III, missense variant). Inhibitor development is rare, and only seen in severe FXI deficiency (<20 IU/dL) upon exposure to plasma-based products. We report our experience of a large cohort of patients with severe FXI deficiency, including seven patients who developed FXI alloinhibitors, their presentation, natural history and subsequent perioperative management.

METHODS

A single-centre retrospective database review of patients with FXI deficiency, including those who have subsequently developed inhibitors, and extraction of clinical, laboratory and genotype data, including operative management records.

RESULTS

A total of 682 patients were identified with FXI deficiency, of whom 113 had FXI < 20 IU/dL and 42 had FXI ≤ 1 IU/dL. Factor XI inhibitors were seen in seven patients, six of whom were homozygous for the type II variant (prevalence of inhibitor with this genotype of 30%, risk of inhibitor upon plasma exposure 50%). FXI inhibitors were not seen, despite similar exposures, in patients with other genotypes. No alteration in bleeding phenotype occurred after inhibitor development and subsequent surgery was managed on 13 occasions with recombinant factor VIIa (rFVIIa), including low doses (15-30 µg/kg), with good haemostasis. The inhibitor spontaneously disappeared in four of seven patients over 1-22 years.

CONCLUSION

FXI inhibitors were only observed in severe FXI deficient patients homozygous for p.Glu135* (null allele) upon plasma or FXI concentrate exposure, with a 30% prevalence. The bleeding phenotype was not altered and inhibitors may disappear with time. Adequate haemostasis in the perioperative setting is achievable with low doses of rFVIIa.

[Congenital factor Ⅺ deficiency: a retrospective analysis of 80 cases]

目的

分析遗传性凝血因子Ⅺ（FⅪ）缺乏症的临床表现、实验室检查、治疗及转归。

方法

对2006年9月至2020年10月就诊于中国医学科学院血液病医院的80例遗传性FⅪ缺乏症患者进行回顾性分析。结果 80例患者中，男33例（41.3％），女47例（58.8％），中位年龄32（2～66）岁。28例（35.0％）存在出血事件，其中自发性出血11例（13.8％），皮肤磕碰后瘀斑或出血9例（11.3％），手术后出血9例（11.3％），女性患者月经过多11例（23.4％），阴道分娩后出血1例（2.1％）。实验室检查表现为活化部分凝血活酶时间（APTT）延长、凝血酶原时间（PT）正常、FⅪ活性（FⅪ∶C）减低。9例（11.3％）患者接受F11基因检测，共检测到11种突变。27例（33.8％）患者接受新鲜冰冻血浆（FFP）治疗，15例（18.8％）手术前预防性输注患者均未发生术中、术后出血。

结论

多数遗传性FⅪ缺乏症患者无出血症状或症状轻微，FⅪ∶C与出血严重程度之间缺乏相关性，FⅪ∶C与F11基因纯合或杂合突变类型具有较好的一致性。预防性输注FFP可有效降低手术出血风险。