Acquired Hemophilia A Presenting as Intramuscular Hematoma

Acquired hemophilia A as a disease of the elderly: A comprehensive review of epidemiology, pathogenesis, and novel therapy

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder characterized by the development of neutralizing autoantibodies (inhibitors) against coagulation factor VIII (FVIII). This review provides an in-depth exploration of AHA, covering its epidemiology, pathogenesis, clinical presentation, diagnosis, complications, and treatment strategies, focusing on recent advancements. AHA can manifest in both men and women with no prior bleeding history. The annual incidence is estimated to be approximately 1 case per million individuals in the general population. The incidence increases significantly with age: the incidence among individuals aged 60 years or older is approximately 3 to 4 cases per million individuals per year. Typically, patients present with an acquired bleeding disorder that is characterized by an isolated, prolonged activated partial thromboplastin time stemming from FVIII deficiency. Diagnosis relies on the detection of neutralizing antibodies using the Nijmegen-modified Bethesda assay. Hemostatic control strategies involve bypassing agents like recombinant activated factor VII, activated prothrombin complex concentrate, and recombinant porcine FVIII for bleeding patients. Emicizumab, a novel bypassing agent, exhibits several potential advantages. In the realm of immunosuppressive treatment for inhibitor eradication, the CyDRi regimen emerged as a remarkable advancement, significantly enhancing the outlook for the management of AHA even in the elderly frail population.

Review of Potential Barriers to Effective Hemostatic Management of Acquired Hemophilia A by Non-Hemophilia Experts in the United States

Acquired hemophilia A (AHA) is an ultra-rare autoimmune disorder caused by autoantibodies against factor VIII. It often presents with life-threatening bleeding to non-hemophilia experts, who have limited awareness of this condition. This review evaluated hemostatic management and identified barriers to optimal management of AHA by non-hemophilia experts in the United States through a literature review. AHA case reports published by non-hemophilia experts from January 2016 through November 2021 in non-hematology journals were critically reviewed for a chronology of clinical course and management, consultation with a hemophilia expert, referencing of available AHA recommendations, discussion of all hemostatic options, and bleed control outcomes; 24 case reports representing 24 patients were identified. Twelve patients had an apparent delay in diagnosis, 17 cases did not seek expert consultation, and 15 did not reference the 2009 International AHA Recommendations, including six in whom hemostatic treatment was not consistent with the recommendations. Of the 17 articles published after the 2017 AHA Guidance, eight did not reference them. Of the five articles published after the 2020 International Recommendations for AHA, three did not reference them. Overall, 14 articles did not discuss all available hemostatic treatment options. Four patients died. Our findings reveal variability in hemostatic management of AHA by non-hemophilia experts in the United States. Lack of AHA awareness remains a primary barrier for optimal management of AHA among non-hemophilia experts. Increasing education about existing AHA guidelines, including available therapies and access to expert care at hemophilia treatment centers, may help improve the outcomes of patients with AHA.

Cross-reacting inhibitors against recombinant porcine factor VIII in acquired hemophilia A: Data from the GTH-AH 01/2010 Study

BACKGROUND

Recombinant porcine factor VIII (rpFVIII, OBI-1, susoctocog alfa) is used for the treatment of acute bleeds in patients with acquired hemophilia A (AHA). Inhibitors in AHA can sometimes cross-react with rpFVIII.

OBJECTIVES

To assess the frequency, strength, and determinants of cross-reactivity.

PATIENTS/METHODS

Baseline samples from 70 patients of the prospective, observational cohort study GTH-AH 01/2010 were assessed for anti-human FVIII and anti-rpFVIII inhibitors using modified Nijmegen-Bethesda assays, as well as anti-human FVIII domain reactivity using enzyme-linked immunoassay (ELISA).

RESULTS

Anti-human FVIII inhibitors were present in all samples ranging between 0.7 and 3891 Bethesda Units (BU)/mL. Inhibitors from 31 of 70 patients (44%) partially inhibited rpFVIII with anti-rpFVIII titers ranging between 0.5 and 471 BU/mL. Anti-rpFVIII titers were ≤5 BU in most patients. Patients with cross-reacting inhibitors, as compared to patients without, had significantly higher anti-human FVIII titers (27.8 versus 5.4 BU/mL) and lower baseline FVIII activity (<1 versus 2.6 IU/dL). The ratio between anti-rpFVIII to anti-human titers was highest for inhibitors involving the C1 domain. Cross-reactivity was very rare, if inhibitors reacted only with the C2 domain of FVIII (6%). An anti-human FVIII titer of >100 BU/mL predicted cross-reactivity with 97% likelihood, whereas an anti-human FVIII titer of <3.8 BU/mL predicted absent cross-reactivity with 90% likelihood.

CONCLUSION

Cross-reacting inhibitors should be considered when choosing a treatment for bleeding patients with AHA. Cross-reactivity is frequent in patients with anti-human FVIII titers of >100 BU/mL.