Acquired Hemophilia A After Neoadjuvant Immunotherapy for Renal Cell Carcinoma.

While many eligible cancer patients now receive immune checkpoint inhibitor (ICI) therapy, a significant number will develop immune-related adverse events (irAEs). Hematologic irAEs are rarely reported, in part due to their infrequent occurrence, but possibly also due to their under recognition. We report a case of acquired hemophilia A (AHA) associated with the use of combined therapy ipilimumab and nivolumab for a patient with renal cell carcinoma and discuss the clinical course and events leading to the diagnosis. AHA is an exceedingly rare yet potentially fatal hematologic irAE and presents most commonly with subcutaneous and mucosal bleeding. The mainstay of treatment for irAE-related AHA includes the use of immunosuppressive therapy to decrease the inhibitor level and risk of recurrent bleeding. This case highlights the importance of early and thorough diagnostic work-up for bleeding disorders in cancer patients with bleeding symptoms and a history of ICI treatment. IrAEs can be difficult to diagnose, and when they are not considered by the clinician, can result in prolonged work-ups without a diagnosis. Ultimately, our patient had a therapeutic response to emicizumab despite a delayed diagnosis. This case underscores the critical need for early recognition and tailored management of rare irAEs to improve patient outcomes.