Relationship between anti-acetylcholine receptor antibodies and the development of post-thymectomy myasthenia gravis in patients with thymoma: a single-center experience

Yusuke Nabe; Teppei Hashimoto; Kanji Tanaka; Yasuhiro Fujita; Katsuma Yoshimatsu; Yukiko Nemoto; Rintaro Oyama; Hiroki Matsumiya; Masataka Mori; Masatoshi Kanayama; Akihiro Taira; Shinji Shinohara; Taiji Kuwata; Masaru Takenaka; Yuko Tashima; Koji Kuroda; Fumihiro Tanaka

doi:10.21037/gs-21-287

Relationship between anti-acetylcholine receptor antibodies and the development of post-thymectomy myasthenia gravis in patients with thymoma: a single-center experience

Gland Surg. 2021 Aug;10(8):2408-2413. doi: 10.21037/gs-21-287.

Authors

Yusuke Nabe¹, Teppei Hashimoto¹, Kanji Tanaka¹, Yasuhiro Fujita¹, Katsuma Yoshimatsu¹, Yukiko Nemoto¹, Rintaro Oyama¹, Hiroki Matsumiya¹, Masataka Mori¹, Masatoshi Kanayama¹, Akihiro Taira¹, Shinji Shinohara¹, Taiji Kuwata¹, Masaru Takenaka¹, Yuko Tashima¹, Koji Kuroda¹, Fumihiro Tanaka¹

Affiliation

¹ Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.

Abstract

Background: Approximately 15-29.6% of patients with thymoma have myasthenia gravis (MG). Some of these patients develop MG after thymectomy despite having no history of MG or related symptoms. Few previous studies have examined the risk factors for the development of post-thymectomy MG in patients with thymoma. Herein, we retrospectively reviewed our institutional experience with patients with thymoma who developed MG after thymectomy.

Methods: Twenty-six patients with thymoma but without MG, who were tested preoperatively for anti-acetylcholine receptor antibody (anti-AChR-Ab) levels, underwent surgical resection at our hospital between 2013 and 2020. Patients with thymic carcinoma were excluded from the study. We evaluated the association of outcomes with preoperative anti-AChR-Ab levels and post-thymectomy MG. We performed a χ² test for bivariate analysis of categorical data. Differences were considered significant at P<0.05.

Results: The characteristics of the 26 patients (median age: 62 years; 8 men, 18 women) were as follows: World Health Organization (WHO) classifications AB (n=8), B1 (n=9), B2 (n=6), B3 (n=1), and others (n=2) and Masaoka stage I (n=12), II (n=9), III (n=3), and IVa (n=2). Among the 26 patients, only five had high (>0.3 nmol/L) preoperative anti-AChR-Ab levels. Post-thymectomy MG occurred in two of the five patients (40%) with high preoperative anti-AChR-Ab levels. A high preoperative serum anti-AChR-Ab titer was significantly associated with post-thymectomy MG (P=0.0267). The anti-AChR-Ab titer was also measured postoperatively in four of the five (80%) patients with high preoperative levels. The anti-AChR-Ab titer decreased in two of these four patients, and neither developed postoperative MG.

Conclusions: Preoperative and postoperative anti-AChR-Ab positivity might be associated with post-thymectomy MG. Therefore, regular measurement of anti-AChR-Ab levels after thymectomy is required.

Keywords: Thymoma; anti-acetylcholine receptor antibody (anti-AChR-Ab); myasthenia gravis (MG); surgery.