As it is still unclear whether the presence of a 4R tau predominant tauopathy is a separate subtype or an earlier/later stage of the disease, we recommend that the diagnosis should be only established in the presence of anti-IgLON5 antibodies in the CSF and the presence of brainstem symptoms including a sleep disorder and/or a supportive HLA genetic background. This evidence concerns the gene IGLON5 and tauopathy.