Autoantibody detection by a live cell-based assay in conventionally antibody-tested triple seronegative Myasthenia gravis

•The prevalence of “clustered” AChR- as well as MuSK- and LRP4- autoantibodies in “triple seronegative” myasthenia gravis assessed by a live cell-based assay (L-CBA) was low.•“Clustered” AChR-autoantibodies were identified in only 4.5% of patients, while none of the patients were positive for MuSK- or LRP4 autoantibodies in l-CBA.•Two out of the three sera that were reactive to the adult AchR showed also binding to the fetal AchR.•The cohort of conventionally tested triple seronegative patients studied is representative when compared to clinical data from the German myasthenia gravis registry.