Natalizumab-related progressive multifocal leukoencephalopathy in Greece

•Early diagnosis and treatment improve PML outcomes.•The proportion of fatal cases of NR-PML may have been underestimated worldwide, as up to now only short follow-up information was available.•An industry-independent NR-PML data registry is needed.

Background & objectivesProgressive 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.MethodsPharmaceutical 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).ResultsThirteen 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).ConclusionsOutcomes 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.