Progressive multifocal leukoencephalopathy and granule cell neuronopathy with novel mutation flanking VP1 C-terminus in natalizumab-extended interval dosing.

Reactivation of a dormant infection with the John Cunningham virus (JCV) can lead to the rare neurologic disorders progressive multifocal leukoencephalopathy (PML) and granule cell neuronopathy (GCN), a cerebellar syndrome with progressing cerebellar atrophy.(1)Here, we present a case of infratentorial PML with concomitant GCN in extended interval dosing (EID) of natalizumab associated with a novel mutation at 7th position after the C-terminus of viral capsid protein VP1 in addition to the common noncoding regulatory region (NCRR) mutation.