Retroperitoneal and lower extremities muscle bleeding in acquired haemophilia A (AHA): Risk factors and implications in disability and survival.

Aim: To assess risk factors of retroperitoneal and lower extremity musculoskeletal bleed in acquired haemophilia (AHA) and perform an objective assessment of disability and influence on survival.

Methods: We included 49 patients with AHA from November 2017 to May 2023. The occurrence of any retroperitoneal or/and lower extremities bleeding manifestation was investigated. On clinical follow-up, we search for compressive femoral neuropathy and quadriceps amyotrophy. The lower extremity functional scale (LEFS) was carried out one year after the last bleeding event in all AHA patients.

Results: A 61.2% of patients in our AHA cohort presented with any retroperitoneal and/or lower extremities musculoskeletal manifestation. Those patients had higher percentage of major bleeding EACH2/ISTH criteria (90% vs. 57%, p = .01), needs of blood transfusions (86% vs. 57% of patients, p = .03), and haemostatic by-pass products (90% vs. 63%, p = .02). Hypertension (HR 2.6, 95% CI 1.1-5.9, p = .02), presence of autoimmune disease (HR 13, 95% CI 1.7-99, p = .01), and inhibitor level > 20 BU (HR 2.6 95% CI 1.0-6.8, p = .04) significantly predicted retroperitoneal/lower extremities clinical manifestations. Most frequent sequelae were quad atrophy (30.6%) and femoral nerve palsy (20.4%). Quad atrophy and LEFS scores under 50 were associated with increased mortality (HR 3, 95% CI 1.1-8.6 and HR 12, 95% CI 3.3-45, respectively).

Conclusion: AHA with retroperitoneal/lower extremities bleeding involvement is of greater severity and shows high disability and worst survival outcomes. Quadriceps atrophy and LEFS scale scoring under 50 predicted mortality in our AHA patients.