HLA-DRB1 and tauopathy: The category of “possible anti-IgLON5-related tauopathy” should be reserved for those cases where clinical data are not available (e.g. due to the retrospective identification of archival cases or other reasons) and ancillary tests (anti-IgLON5 antibodies and/or HLA-DRB1*1001 and HLA-DQB1*0501 alleles) could not be performed.