| Summary: | Shinsaku Imashuku,1 Naoko Kudo,1 Kagekatsu Kubo,1 Katsuyasu Saigo,1 Nanako Okuno,2 Kaoru Tohyama21Division of Hematology, Takasago-seibu Hospital, Takasago, Japan; 2Department of Laboratory Medicine, Kawasaki Medical School, Kurashiki, JapanBackground: 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.Keywords: acquired hemophilia A, chronic neutrophilic leukemia, JAK2 kinase, V617 mutation, rituximab
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