Development of acquired hemophilia A during treatment of multiple myeloma with lenalidomide.

We describe a 67-year-old female demonstrating symptomatic multiple myeloma (MM) with anemia and bone lesions initially diagnosed in 2009. Although a partial response was achieved after bortezomib and dexamethasone treatment, MM recurred in 2012. Therefore, treatment with lenalidomide, cyclophosphamide, and dexamethasone was commenced. Coagulation tests conducted prior to the chemotherapy were normal. Lenalidomide was discontinued after 10 days due to exacerbation of renal dysfunction. Simultaneously, activated partial thromboplastin time (APTT) was prolonged to 89.5 seconds. The mixing test showed an inhibitor pattern, with factor VIII at 2% and factor VIII inhibitor at 4.85 BU/ml. A diagnosis of acquired hemophilia A was made, and treatment with prednisolone was started, after which APTT improved to 36.4 seconds and factor VIII inhibitor decreased to 1.09 BU/ml. The factor VIII inhibitor level again increased concomitantly with restarting lenalidomide, which was, therefore, discontinued, while immunosuppressive therapy was administered with the addition of cyclophosphamide. Factor VIII inhibitor gradually disappeared from the patient's blood over the next four months. To the best of our knowledge, this is the first description of lenalidomide as a possible cause of acquired hemophilia A. Our experience indicates that we need to pay attention to acquired hemophilia A after initiating lenalidomide therapy in patients with hematologic malignancies.