Subclinical myasthenia gravis in thymomas

• Published in: Lung cancer (Amsterdam, Netherlands) Vol. 152; pp. 143 - 148
• Main Authors: Marcuse, Florit, Hochstenbag, Monique, Hoeijmakers, Janneke G.J., Hamid, Myrurgia Abdul, Damoiseaux, Jan, Maessen, Jos, De Baets, Marc
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01-02-2021
• Subjects: Anti-acetylcholinereceptor-antibodies; Myasthenia gravis; Thymectomy; Thymomas; Thymomas; Thymectomy; Myasthenia gravis; Anti-acetylcholinereceptor-antibodies
• ISSN: 0169-5002; 1872-8332
• DOI: 10.1016/j.lungcan.2020.12.010

•Subclinical myasthenia gravis is not uncommon in thymomas.•Transition of subclinical myasthenia to clinical myasthenia gravis is a matter of time.•Positive anti-AChR-antibodies are highly significant for the presence or development of myasthenia gravis in thymomas.•Positive anti-AChR-antibodies should trigger considerations of anesthetic-, oncological- and neurological treatment in thymomas.•Testing anti-AChR-antibodies in suspected thymomas is part of the pre-surgical screening by the pulmonary oncologist. Therefore it is malpractice if the antibody status is unknown in suspected thymomas at the time of a thymectomy.
A proportion of thymoma-patients without a history of myasthenia gravis (MG) before thymectomy, appears to have positive anti-AChR-antibodies in the serum. These subclinical MG-patients could be underdiagnosed because analyzation of anti-AChR-antibodies in thymomas is not always performed in patients who did not experience neurological symptoms. The prevalence and long-term outcomes of subclinical MG are never described in literature yet.
We retrospectively analyzed 398 consecutive patients who underwent a robotic-assisted thoracoscopic surgery at the Maastricht University Medical Center+ (MUMC+) between April 2004 and December 2018. In the MUMC+, a robotic approach is the standard surgical approach in patients with thymic diseases. Inclusion criteria were thymomas, thymectomy performed in the MUMC + with a follow-up of at least one year and age above 18 years old. Exclusion criteria were patients with thymic carcinomas, refused participation, or those who were lost to follow-up.
Of the 102 included thymoma-patients, 87 patients (85 %) were tested for anti-AChR-antibodies before thymectomy, of which 57 patients were diagnosed with clinical MG and seven subclinical MG-patients were found. Of the 15 patients who were not tested for anti-AChR-antibodies, four more subclinical MG-patients were discovered in the years after thymectomy. The median follow-up time was 62 months. In total, 11 subclinical MG-patients were found, with a mean age of 54 years and predominantly females (64 %). Ten subclinical MG-patients (91 %) developed clinical-MG, within six years after thymectomy. Immunosuppressive drugs were prescribed in five patients. Four patients were diagnosed with a recurrence of the thymoma. No surgical mortality was reported. Two patients died due to a myasthenic crisis.
The prevalence of subclinical MG in thymomas was found to be 10.8 %. One in four patients who experienced no neurological symptoms before thymectomy, appeared to have anti-AChR-antibodies and 91 % of these patients developed clinical MG within six years after the thymectomy. Analyzing anti-AChR-antibodies in the serum is recommended in all suspected thymomas before a thymectomy is performed.