Nationwide survey of Lambert-Eaton myasthenic syndrome in Japan

Abstract

BackgroundThere was no nationwide epidemiological study of Lambert-Eaton myasthenic syndrome (LEMS) in Japan; therefore, we conducted a nationwide survey.MethodsFor 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.ResultsWe 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).ConclusionsThe 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.

The Japanese clinical guidelines 2022 for myasthenia gravis and Lambert–Eaton myasthenic syndrome

“…The prevalence of LEMS in Japan was estimated to be 0.27 per 100 000 44 . Core symptoms of LEMS are weakness of proximal extremities, decreased tendon reflexes and autonomic symptoms.…”

A rare case of concomitant Lambert–Eaton myasthenic syndrome and syndrome of inappropriate antidiuretic hormone secretion in a patient with small cell lung carcinoma

“…LEMS may occur as an autoimmune disease without malignancy (NT-LEMS), or as a paraneoplastic disorder (CA-LEMS) that is most commonly associated with small cell lung carcinoma (SCLC) [ 2 , 3 ]. LEMS is a rare disease with a prevalence of 2.7 per million population, and 54%–71.4% of LEMS patients have concomitant or subsequent SCLC [ 3 , 4 ].…”

Autoimmunity to voltage‐gated calcium channels

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Recently, a nationwide survey of Lambert-Eaton myasthenic syndrome (LEMS) was conducted by the Ministry of Health, Labour and Welfare research group and reported that the number of LEMS patients in Japan in 2017 was estimated to be 348. 1 In September 2021, the P/Q-type voltage-gated calcium channel (VGCC) antibody assay for the diagnosis and treatment of LEMS was covered by insurance. Furthermore, in May 2022, practical guidelines for myasthenia gravis (MG) and LEMS 2022 were compiled by the Japan Neurological Society.

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