Too much of a good thing?

Abstract

In this issue of Neurology ®, Tan et al.1 divide the patients with immune reconstitution inflammatory syndrome (IRIS) occurring with natalizumab-associated progressive multifocal leukoencephalopathy (PML) into 2 groups: those with early PML-IRIS, in whom IRIS developed before the institution of plasma exchange/immunoadsorption (PLEX/IA); and those with late PML-IRIS, in whom IRIS developed only after PLEX/IA. IRIS was defined as clinical and radiographic worsening after a period of improvement or stability. They argue that the neurologic outcome as determined using the Expanded Disability Scale Score (EDSS) was worse in the former group, namely, those with features of IRIS developing before the use of PLEX/IA, but this observation did not reach statistical significance. Survival between the 2 groups was comparable. The present study follows on the heels of the analysis of the first 28 cases of natalizumab-associated PML reported last year.2 As in the earlier study, most, if not all, patients with natalizumab-associated PML developed IRIS. The observation that the earlier a robust immune response to the PML-causing JC virus appears, the worst the prognosis, is counterintuitive. The ability to restore normal immune function …