GRID2 and cerebellar ataxia: A potential pathogenic role of anti-GluRδ2 in ACA is conceivable given that GluRδ2 is predominantly expressed in PCs, GluRδ2 is present on the cell surface, anti-GluRδ2 was detected in the CSF in some cases, GluRδ2 mutations are associated with ataxia (see below), and PEX had a therapeutic effect in individual patients.