New and Old Concepts and Strategies for Progressive Multifocal Leukoencephalopathy

Abstract

There has been recent progress in the area of John-Cunningham virus (JCV) infection and progressive multifocal leukoencephalopathy (PML). New drugs and better reporting identify new risk cohorts and importantly development of new risk assessment strategies. The clinical presentation has not changed, but presentation of rarer forms of JCV infection are now apparent. Brain magnetic resonance imaging (MRI) continues to be a pillar of PML diagnosis. The imaging correlation with pathology and the new understanding of the biology and improved methods to detect JCV significantly help with recent diagnostic criteria. Unfortunately a small number of trials for specific treatment of PML have not proven beneficial, and the possibility remains to improve the JCV- specific immune response. Sometimes this response creates an exacerbation of neurological features – immune reconstitution inflammatory syndrome – that helps resolve the infection but can cause damage in itself. Overall, the prognosis of PML has improved with much lower mortality but still severe neurological deficits.