Challenges in myasthenia gravis diagnosis: an analysis of the diagnostic process of myasthenia gravis in a specialized clinic.

Diagnosis of MG can be complicated and consequent delays in diagnosis can lead to potentially life-threatening situations. We designed a retrospective, observational study to review the diagnostic process of patients with suspicion of MG in real-world practice, identifying pitfalls and the most common mimic entities. Of the 561 patients referred with suspected MG, it was ruled out in 167 (29 %). An alternative diagnosis was reached in 53.9 %, showing high heterogeneity among these entities. During the diagnostic process, the cornerstone was the clinical picture, and in 30 % of the mimic group no further studies were needed. Regarding antibodies, 7.9 % of patients in MG mimic group had a previous, positive anti-AChR determination, later confirmed as a false positive result. Up to 19 % of patients in the mimic group showed abnormalities in the single fiber electromyography. This study highlights the diagnostic challenge in patients with suspected MG, especially in seronegative cases. In these patients, it took a mean of >2 years to rule out MG, and up to 23 % of these patients received immunosuppressants during this process.