Abstract
Cytomegalovirus (CMV) infection in patients with hematologic malignancies who have not undergone stem cell transplantation remains poorly understood. Reports of clinically significant CMV infections in patients receiving Bruton Tyrosine Kinase inhibitors (BTKi) are rare. We present a case of ganciclovir-resistant CMV encephalitis in a patient with mantle cell lymphoma (MCL) treated with pirtobrutinib (a third generation BTKi). This case highlights the importance of maintaining a high index of suspicion for CMV infection in patients with hematologic malignancies, including those receiving therapies traditionally considered to carry a lower risk of opportunistic infections.