Nationwide survey of Lambert-Eaton myasthenic syndrome in Japan

Hiroaki Yoshikawa; Yumi Adachi; Yosikazu Nakamura; Nagato Kuriyama; Hiroyuki Murai; Yoshiko Nomura; Yasunari Sakai; Kazuo Iwasa; Yutaka Furukawa; Satoshi Kuwabara; Makoto Matsui

doi:10.1136/bmjno-2022-000291

Nationwide survey of Lambert-Eaton myasthenic syndrome in Japan

BMJ Neurol Open. 2022 Sep 5;4(2):e000291. doi: 10.1136/bmjno-2022-000291. eCollection 2022.

Authors

Hiroaki Yoshikawa¹, Yumi Adachi¹, Yosikazu Nakamura², Nagato Kuriyama^{3

4}, Hiroyuki Murai⁵, Yoshiko Nomura⁶, Yasunari Sakai⁷, Kazuo Iwasa⁸, Yutaka Furukawa⁹, Satoshi Kuwabara¹⁰, Makoto Matsui¹¹

Affiliations

¹ Health Service Center, Kanazawa University, Kanazawa, Ishikawa, Japan.
² Public Health, Jichi Medical University, Shimotsuke, Tochigi, Japan.
³ Department of Social Health Medicine, Shizuoka Graduate University of Public Health, Shizuoka, Japan.
⁴ Department of Epidemiology for Community Health and Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan.
⁵ Neurology, International University of Health and Welfare, Otawara, Tochigi, Japan.
⁶ Pediatric Neurology, Yoshiko Nomura Neurological Clinic for Children, Tokyo, Japan.
⁷ Department of Pediatrics, Kyushu University, Fukuoka, Japan.
⁸ Health Science, Ishikawa Prefectural Nursing University, Kahoku-gun, Ishikawa, Japan.
⁹ Department of Neurology and Neurobiology of Aging, Kanazawa University, Kanazawa, Ishikawa, Japan.
¹⁰ Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan.
¹¹ Neurology, Kanazawa Medical University, Kahoku-gun, Ishikawa, Japan.

Abstract

Background: There was no nationwide epidemiological study of Lambert-Eaton myasthenic syndrome (LEMS) in Japan; therefore, we conducted a nationwide survey.

Methods: For the first survey, we sent survey sheets to randomly selected medical departments (n=7545) to obtain the number of LEMS who visited medical departments between 1 January 2017 and 31 December 2017. For the second survey, we sent survey sheets to the corresponding medical departments to obtain clinical information on LEMS.

Results: We received 2708 responses (recovery rate: 35.9%) to the first survey. We estimated the number of LEMS as 348 (95% CI 247 to 449). The prevalence was 2.7 (95% CI 1.9 to 3.5) in 1 000 000 population. As a result of the second survey, we obtained 30 case records of 16 men and 14 women. Fourteen patients (46.7%) had a tumour, and 10 out of 14 tumours were small-cell lung carcinoma (71.4%). There was a predominance of men in the LEMS with tumour (paraneoplastic LEMS, P-LEMS) (n=11, 78.6%) and women in the LEMS without tumour (a primary autoimmune form of LEMS, AI-LEMS) (n=11, 68.8%) (p=0.0136). The onset age (mean (SD)) for the P-LEMS was 67.1 (9.0), and that for AI-LEMS was 57.8 (11.2) years old (p=0.0103). The disease duration (median) for P-LEMS was 2 years, and for AI-LEMS was 7.5 years (p=0.0134).

Conclusions: The prevalence of LEMS in Japan is similar to that in other countries. There are predominances of men in P-LEMS and women in AI-LEMS.

Keywords: clinical neurology; epidemiology; neuromuscular.