Neonatal encephalitis and white matter injury: More than just inflammation?

Abstract

In this issue of the Annals, Verboon-Maciolek and coworkers show that human parechovirus (HPeV), specifically HPeV3, is an important cause of neonatal viral encephalitis.1 The six serotypes of HPeVs that are included in the genus Parechovirus are small single-stranded (ss) RNA viruses belonging to the family Picornaviridae.2, 3 These viruses bear many similarities with another and better-known Picornaviridae genus, Enterovirus (EV). Indeed, the genus Parechovirus began with the reclassification of echovirus 21 and 22 as HPeV1 and HPeV2 because of molecular and genetic differences from the remainder of EV. These differences are important because they explain, in part, why the usual polymerase chain reaction (PCR) testing for EV does not detect HPeV. Thus encephalitic infection by HPeV3 has been overlooked in the past, one important point of the current article. (Neonatal encephalitis by other HPeV subtypes is extremely rare and not discussed further.) The encephalitis caused by HPeV3 infection as well as by EV is associated with neonatal seizures and with apparent cerebral white matter injury.1, 4 The current report has important implications concerning the etiology of neonatal viral encephalitis, the differential diagnosis of neonatal seizures, and the pathology and pathophysiology of the white matter injury.