Myasthenia gravis misdiagnosis in the era of innovative therapies: Uncovering pitfalls and patterns.

Increased disease awareness and advanced serological tests have improved myasthenia gravis (MG) diagnosis. However, the risk of misdiagnosis remains. The aim of this study was to evaluate the rate and causes of MG misdiagnosis in a tertiary MG clinic. We analyzed medical records from patients diagnosed with MG who were referred to our tertiary clinic for a second opinion between 2019 and 2024. Of the 144 patients originally included in the analysis, 15 were excluded due to insufficient data. MG diagnosis was not confirmed in 26/129 patients (20.2%). None of these 26 patients had clinical symptoms consistent with MG; 13 patients (50%) were seronegative; 12 had AChR antibodies (Abs) (detected by radioimmunoassay -RIA in 6 and by ELISA in the other 6 patients); a single patient had MuSK-Abs. Fixed and live cell-based assays were negative in all these 26 cases. Predictors of MG misdiagnosis included absence of MG-typical clinical features, younger age at onset, female sex, non-response to or intolerance of pyridostigmine, Ab testing by ELISA. MG misdiagnosis is not uncommon and often leads to unnecessary treatment. Our findings confirm the relevance of typical clinical pattern, proper antibody assays, and expertise in neurophysiological testing to establish MG diagnosis.