Aspergillus fumigatus brain abscess in an immunocompromised patient receiving a second-generation Bruton Tyrosine Kinase inhibitor (BTKi).

Chronic lymphocytic leukemia (CLL) is a frequent type of adult leukemia. Bruton Tyrosine Kinase inhibitors (BTKi) are first-line treatments for CLL. Despite being efficient, BTKi have also been associated with significant side effects, including arrhythmias, hemorrhagic complications, and opportunistic infections. Zanubrutinib is a second-generation BTKi that recently received FDA approval for CLL and is associated with improved outcomes and a better safety profile compared to first-generation BTKi. In the present study, we report a case of a patient with CLL, with an in-range absolute neutrophil count and an isolated Aspergillus fumigatus brain abscess mimicking a brain tumor. The lesion was excised "en bloc", and lesion cultures revealed Aspergillus fumigatus sensitive to amphotericin and voriconazole. The patient received postoperative treatment with voriconazole. While invasive fungal infections with brain involvement have been previously reported, to our knowledge, this is the first documented case of an isolated Aspergillus fumigatus brain abscess in a patient receiving zanubrutinib.