HLA-DR9HLA-DR09 is a HLA-DR serotype that recognizes the DRB1*0901 gene product.SerologyThe serological reaction of DR9 is relatively good. The serology of DRB1*0902 to *0906 serotypes is unknown.Disease associationsDRB1*0901: Early childhood myasthenia gravisExtended linkageDRB1*0901:DQA1*0301:DQB1*0303 haplotype: Early childhood myastenia gravisGenetic linkageHLA-DR9 is genetically linked to HLA-DR53, and HLA-DQ3 and DQ9 serotypes.