Progressive multifocal leukoencephalopathy complicating untreated chronic lymphatic leukemia: Case report and review of the literature

Highlights • PML in a therapy naïve patient with CLL is a rare disease complication. • Altered immune response and prior treatment history are crucial for the pathogenesis. • In this case, only CLL associated alterations of the immune status are responsible. • In CLL an important differential diagnosis is direct CNS-involvement. • Treatment of PML in patients with hematological malignancies is challenging.