Natalizumab-related progressive multifocal leukoencephalopathy in Greece

Abstract Background & objectives Progressive multifocal leukoencephalopathy (PML) may complicate natalizumab treatment in multiple sclerosis patients. We sought to characterize the clinical and laboratory features of natalizumab-related PML (NR-PML) cases from Greece. Methods Pharmaceutical industry, national drug authorities and all neurology departments within the Greek territory were asked to provide data for cases of NR-PML until October 2012. Collected cases were classified according to their level of diagnostic certainty using the five-level system introduced by Mentzer et al. (2012). Results Thirteen NR-PML cases were identified by the neurology departments. Data were provided for only 9 cases. PML manifestations appeared after a median number of 40 (21–52) natalizumab infusions. All but two patients were treated with plasma exchange and some were treated adjunctively with mirtazapine while the others were treated with mefloquine. IRIS developed in 6 cases after a median time of 6 (2–10) weeks from PML presentation and were treated with different regimens of corticosteroids. PML was fatal in 3 cases. The median EDSS after a median follow-up time of 12 (8–23) months in the surviving cases was 4.75 (2–8.5). Conclusions Outcomes for collected NR-PML cases varied from death to returning to baseline. Close surveillance is essential for early diagnosis and treatment of NR-PML patients.