Original Research
AB040. Subclinical myasthenia gravis after thymectomy: a 20-year retrospective cohort study
Florit Marcuse1, Janneke Hoeijmakers2, Myrurgia Abdul Hamid3, Jamie Romeo4, Jos Maessen4, Stephanie Peeters5, Jan Damoiseaux6, Pilar Martinez7, Monique Hochstenbag1, Marc De Baets7
1Department of Pulmonology, Maastricht University Medical Comprehensive Cancer Center, Maastricht, the Netherlands;
2Department of Neurology, Maastricht University Medical Center+, Maastricht, the Netherlands;
3Department of Pathology, Maastricht University Medical Center+, Maastricht, the Netherlands;
4Department of Cardiothoracic Surgery, Maastricht University Medical Center+, Maastricht, the Netherlands;
5Department of Radiation Oncology (Maastro Clinic), Maastricht University Medical Center+, Maastricht, the Netherlands;
6Central Diagnostic Laboratory, Maastricht University Medical Center+, Maastricht, the Netherlands;
7School for Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands.
Correspondence to: Florit Marcuse, MD, PhD. Department of Pulmonology, Maastricht University Medical Center+, P. Debyelaan 25, 6229 HX, Maastricht, Maastricht, the Netherlands. Email: florit.marcuse@mumc.nl.
Background: Subclinical myasthenia gravis (subMG) is characterized by circulating anti-acetylcholine receptor antibodies (anti-AChR-ab) without clinical symptoms of myasthenia gravis (MG). Previously, we reported a 10.8% incidence of sMG in 102 patients with resected thymoma. The current study aims to assess the incidence and clinical course of sMG in a larger thymoma cohort following thymectomy.
Methods: We retrospectively analyzed 248 consecutive patients who underwent robotic-assisted thoracoscopic surgery for thymoma at the Maastricht University Medical Center+ between 2004 and 2024. Anti-AChR-ab was found positive in cases of >0.25 nmol/L measured by radioimmunoassay. Inclusion criteria were total thymectomy for thymoma, age ≥18 years, and a minimum follow-up of 6 months. MG symptoms were classified using the Myasthenia Gravis Foundation of America (MGFA) system. A neurologist specialized in neuromuscular disorders was consulted pre-thymectomy in patients with MG or subMG. Pearson’s chi-squared and Fisher’s exact test were statistically significant in the case P<0.05.
Results: Anti-AChR-ab were analyzed in 228 thymoma patients (91.9%) pre-thymectomy and 6 patients post-thymectomy (Figure 1). Symptomatic MG was observed in 129 patients (52.0%). The development to symptomatic MG was observed in 14 patients (53.8%), although the median follow-up was also significantly longer in patients who developed symptomatic MG compared to subMG patients who did not develop symptoms (58.0 vs. 26.0 months, P=0.02). The most frequent time of development of symptomatic MG was directly after thymectomy (3 patients) and between 12 and 24 months of follow-up (6 patients). Ten subMG patients required cholinesterase inhibitors or immunosuppressive therapy. Five patients died during follow-up, including two from myasthenic crisis.
Conclusions: The incidence of subMG among patients with thymoma was 10.5%. A substantial proportion (54%) progressed to symptomatic MG over time, with peak incidences directly after thymectomy and between 12–24 months of follow-up post-thymectomy, underscoring the need for prolonged attention for developing MG symptoms and thorough pre-operative assessment. Further research is necessary to investigate the mechanisms of subMG and the development of symptomatic MG post-thymectomy. Specific guideline recommendations could help clinicians with the surgical, oncological, and neurological workup of patients with subMG.
Keywords: Subclinical myasthenia gravis (subMG); thymoma; thymectomies; anti-acetylcholine receptor antibodies (anti-AChR-ab)
Acknowledgments
None.
Funding: None.
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-25-ab040/coif). J.H. received grants from Prinses Beatrix Spierfonds (W.OK17-09, W.TR22-01 en W.OR24-04). She also is medical advisor of the Dutch patient organization for neuromuscular disorders (Spierziekten Nederland and ‘Small fiber neuropathy’), board member of the Dutch Center for Neuromuscular Diseases, and management member of the Euro-NMD Peripheral Nerve Diseases working group. S.P. received Hanarth grant, financing for the INTHYM project, on artificial intelligence for histopathological classification and recurrence prediction of thymic epithelial tumor. But this project is not related to the current abstract. The other authors have no conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the ethics board of Maastricht University Medical Center+, Maastricht, the Netherlands (No. 2018-0491, 2018-0491-A-11), and individual consent for this retrospective analysis was waived.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
doi: 10.21037/med-25-ab040
Cite this abstract as: Marcuse F, Hoeijmakers J, Abdul Hamid M, Romeo J, Maessen J, Peeters S, Damoiseaux J, Martinez P, Hochstenbag M, De Baets M. AB040. Subclinical myasthenia gravis after thymectomy: a 20-year retrospective cohort study. Mediastinum 2025;9:AB040.
