Subclinical myasthenia gravis in thymomas

Abstract

A proportion of thymoma-patients without a history of myasthenia gravis (MG) before thymectomy, appears to have positive anti-AChR-antibodies in the serum. 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. 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.