Rituximab for managing acquired hemophilia A in a case of chronic neutrophilic leukemia with the JAK2 kinase V617F mutation

BACKGROUND: Acquired hemophilia A is rarely found in association with myeloproliferative neoplasms, such as the JAK2 kinase V617F mutation-positive chronic neutrophilic leukemia (CNL). CASE REPORT: An 80-year-old Japanese male was diagnosed with acquired hemophilia A. He had compartment-like symptoms due to soft tissue hemorrhage in his left forearm and right lower extremity. A blood examination showed neutrophilia with a white blood cell count of 31,900/μL (91.9% neutrophils), an activated partial thromboplastin time of 69.0 seconds, coagulation factor VIII (FVIII) < 1.0%, and anti-FVIII inhibitor, 190 BU/mL. The bleeding episodes were controlled with intravenous activated prothrombin complex concentrate (FEIBA(®)) followed by recombinant factor VIIa (NovoSeven(®)). In addition, oral prednisolone (maximum dose, 30 mg/day) plus four doses of rituximab effectively suppressed anti-FVIII inhibitor levels while simultaneously reducing the neutrophil count. CNL with the JAK2 kinase V617F mutation was identified as the underlying disease. CONCLUSION: This report describes the effectiveness of a combination of prednisolone and rituximab in managing acquired hemophilia A in an elderly man with a rare case of JAK2 kinase V617F mutation-positive CNL.