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Incidence and causes of overdiagnosis of myasthenia gravis
Nirmal Andrapalliyal1, Benjamin Claytor1, Yuebing Li1
1Department of Neurology, Neurological Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA.
Introduction/Aims:
We have encountered non-myasthenic patients being given a diagnosis of myasthenia gravis (MG). This study aims to investigate the frequency of, and factors contributing to, overdiagnosis of MG.
Methods:
This is a retrospective analysis of patients referred to our tertiary neuromuscular center for evaluation due to a previously suspected/confirmed MG diagnosis during a 6-year span.
Results:
A total of 531 patients sought a second opinion regarding their MG diagnosis, and 77 (14.5%) were found to have non-myasthenic conditions. A total of 11 patients tested positive for acetylcholine receptor (AChR) antibodies. Repeated AChR antibodies became negative in five patients while in four patients, AChR binding antibody titers were persistently low. In seven patients, striational antibody was the only positive antibody identified. In 25 patients, a prior electrodiagnostic (EDX) study was deemed positive, including 14 patients with abnormal repetitive nerve stimulation (RNS) and 12 with abnormal single fiber electromyography (SFEMG). Technical issues were noted on prior RNS studies in 8 patients, and repeat RNS was negative in 10 patients. In eight patients with previously abnormal SFEMG, results showed minimal or equivocal abnormalities. In two patients, a repeat SFEMG was normal. Further analysis revealed atypical clinical presentation, deceptively positive ice pack test, clinically insignificant antibody result and misleading EDX finding as main contributors to MG overdiagnosis.
Discussion:
Overdiagnosis of MG is not uncommon, and occurs more frequently in seronegative patients. To make an accurate diagnosis of MG, there is a need to recognize atypical presentations, and avoid overreliance on minor or non-specific serological and electrodiagnostic findings.
Insights
Overdiagnosis of myasthenia gravis (MG) is common, with 14.5% of patients misdiagnosed. Factors include atypical symptoms and misleading tests, especially in seronegative cases. Accurate diagnosis requires careful evaluation.
Area of Science:
- Neurology
- Clinical Diagnostics
Background:
- Myasthenia gravis (MG) is an autoimmune disorder affecting neuromuscular junctions.
- Accurate diagnosis is crucial for effective treatment and patient outcomes.
- Overdiagnosis of MG can lead to inappropriate management and delayed diagnosis of correct conditions.
Purpose of the Study:
- To investigate the frequency of myasthenia gravis overdiagnosis.
- To identify factors contributing to the misdiagnosis of MG.
Main Methods:
- Retrospective analysis of 531 patients referred for a second opinion on their MG diagnosis.
- Review of clinical presentation, serological tests (acetylcholine receptor antibodies, striational antibodies), and electrodiagnostic studies (repetitive nerve stimulation, single-fiber electromyography).
Main Results:
- 77 out of 531 patients (14.5%) with a suspected or confirmed MG diagnosis were found to have non-myasthenic conditions.
- Contributing factors included atypical clinical presentations, misleading antibody results (low titers, seronegative status), and electrodiagnostic abnormalities.
- Technical issues and equivocal findings were noted in prior electrodiagnostic studies.
Conclusions:
- Overdiagnosis of myasthenia gravis is a significant issue, particularly in seronegative patients.
- Accurate diagnosis necessitates careful consideration of atypical presentations and avoidance of over-reliance on non-specific serological and electrodiagnostic findings.
- Re-evaluation of suspected MG cases is important to ensure correct diagnosis and management.
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