Longitudinally extensive transverse myelitis (LETM) is a condition shown to confer high risk of conversion into neuromyelitis optica (NMO). Increasing evidence from immunological and histopathological studies suggests that LETM is an autoimmune disorder caused by pathogenic antibodies to aquaporin-4 (AQP4-Ab), the most abundant water channel in the CNS, at least in a subset of patients. However, cases of infectious or parainfectious NMO/LETM (mostly associated with herpes zoster) have been repeatedly reported in the previous literature, raising the question of aetiological diversity in NMO/LETM. Here we present a case of acute LETM in a 63-year-old patient occurring two weeks after reactivation of varicella zoster virus (VZV). Serological testing revealed antibodies to AQP4. Plasma exchange was paralleled by disappearance of AQP4-Ab and sustained clinical improvement. Our observations provide further evidence for a pathogenic role of AQP4-Ab in LETM and suggest that AQP4-Ab associated auto-immunity should be considered also in apparently infectious/parainfectious settings.