Tyrosine Kinase Inhibitor-induced Cerebrovascular Occlusion Presenting with Moyamoya Disease-like Stenosis of the Circle of Willis.

Vascular occlusive events are notable adverse effects of tyrosine kinase inhibitors (TKIs), which are promising treatments for chronic myeloid leukemia (CML). We herein report the case of a patient with CML who developed cerebrovascular occlusion of the circle of Willis during TKI treatment. Our patient did not meet the diagnostic criteria for moyamoya disease due to the insignificant development of moyamoya vessels. The lack of moyamoya vessel development may be explained by the suppression of tyrosine kinases that are responsible for angiogenesis. Cerebrovascular occlusion of the circle of Willis, without significant development of moyamoya vessels, may be an important phenotype of TKI-associated vasculopathy.