Progressive multifocal leukoencephalopathy: A review

Progressive multifocal leukoencephalopathy (PML) is a CNS demyelinating disease caused by papovavirus (JC virus or JCV) infection of oligodendrocytes. It was initially described in the late 1950s and its causative virus, known as the JCV, was isolated in the 1970s. PML is clearly associated with immunosuppression. Currently, AIDS is the most common cause of immunosuppression in patients with PML, although before the AIDS epidemic, cancer and its treatment, autoimmune disease, and granulomatous processes were PML's most common settings. The JCV virus is acquired eddy in life and remains latent in B lymphocytes; with immunosuppression, it replicates and spreads. Entrance into the CNS results in the characteristic pathological features of demyelination, abnormal oligodendroglial nuclei, and giant, often bizarre, astrocytes. Inflammation is usually sparse and confined to macrophages. The multifocal nature of the demyelination produces the varied clinical findings in affected patients. Focal neurological signs and symptoms herald the disease, and cognitive impairment, motor weakness, and visual deficits are the most common presenting features. The diagnosis is supported by history and clinical examination as well as by neuroimaging. Biopsy is the only premortem procedure that confirms the diagnosis. The prognosis is almost universally fatal. Ongoing studies may provide effective treatment options in the near future, but current therapies are ineffective.