A case of a cerebellar form of progressive multifocal leukoencephalopathy in a patient undergoing peritoneal dialysis.

Progressive multifocal leukoencephalopathy (PML), a severe demyelinating disease of the central nervous system, is caused by the reactivation of the polyomavirus JC virus (JCV). It favors the cerebrum and typically occurs in patients with immunodeficiencies, with a progressive course and fatal outcome in the majority of cases. However, the cerebellar form of PML, characterized by isolated posterior fossa lesions, such as those in the cerebellum or brainstem at disease onset, is rare, and reports of its occurrence in peritoneal dialysis (PD) patients are lacking. In this paper, we describe a rare case of a cerebellar form of PML in a PD patient. A 64-year-old man undergoing PD was referred to our hospital for anorexia, nausea, and vomiting in the past month. He had finger-to-nose test abnormalities, gaze-directed nystagmus, and scanning speech. He was diagnosed with the cerebellar form of PML based on his progressive cerebellar symptoms, the typical magnetic resonance imaging findings, and the presence of JCV-DNA in the cerebrospinal fluid polymerase chain reaction test. He developed nocturnal delirium, aggravated disquiet, and died of pneumonia on the 69th day. Clinicians should consider the cerebellar form of PML as a differential diagnosis if PD patients develop progressive cerebellar symptoms.