B‐Lymphoblastic Leukemia With Isolated Central Nervous System Relapse Mimicking a Vestibular Schwannoma

ABSTRACT The central nervous system (CNS) is the most common site of extramedullary relapse in acute lymphoblastic leukemia (ALL). However, the diagnosis may be challenging due to its protean manifestations. A 64‐year‐old male reported right‐sided hearing loss with intermittent bilateral occipitotemporal headaches during a clinic follow‐up for Ph + B‐ALL. His yearling and neurological symptoms persisted, with two unremarkable MRI brains. However, a repeat MRI showed findings suspicious for a vestibular schwannoma. Isolated CNS relapse of B‐ALL was subsequently confirmed on lumbar puncture. He received intrathecal and dasatinib therapy, which was complicated by cytomegalovirus (CMV) colitis and Granulicatella adiacens native aortic valve infective endocarditis. Subsequently, he received craniospinal irradiation followed by haploidentical allogeneic stem cell transplant (alloSCT) and has remained in molecular remission. This case of isolated CNS relapse of B‐ALL with BCR::ABL1 fusion illustrates some diagnostic and treatment challenges, including presenting symptoms and imaging findings that mimicked a vestibular schwannoma. The case also contributes to the limited literature reporting systemic CMV infections associated with dasatinib. In addition, it extends the spectrum of reported dasatinib‐associated infections to include Granulicatella adiacens .