Progressive multifocal leukoencephalopathy (PML) which is a severe demyelinating disease of the central nervous system (CNS), is caused by a human polyomavirus known as JC virus (JCV). PML is seen primarily in immunosuppressed (AIDS, organ transplant or malignancy) patients. In this report, a case of PML that developed in a 75-years-old female patient with no known immunosuppression was presented. The patient was admitted to the emergency department with complaints of headache and burning sensation in head. Cerebrospinal fluid (CSF) examination revealed increase in lymphocytic cells. Since lesions compatible with tuberculoma were detected in brain tissue by magnetic resonance imaging, antituberculous therapy initiated empirically. The disease exhibited a progressive course and all the serological, molecular, microbiological and biochemical tests performed in blood and CSF failed to identify the causative agent. Pathological and immunohistochemical examination of the brain biopsy specimens demonstrated demyelinating disease. Brain biopsy, CSF, serum and urine specimens were investigated by real-time polymerase chain reaction specific for JCV and JCV-DNA was detected in the urine samples. Follow-up visits of the patient indicated a progressive course. In conclusion, after ruling out the other primary causes, JCV should be investigated in patients with demyelinating CNS disease even in the absence of significant immunosuppressive condition. Elderly patients should be considered in the risk group for demyelinating disease of CNS due to JCV.