Characteristics of myasthenia gravis according to onset-age: Japanese nationwide survey

• Published in: Journal of the neurological sciences 2011-06, Vol.305 (1), p.97-102
• Main Authors: Murai, Hiroyuki, Yamashita, Natsumi, Watanabe, Makoto, Nomura, Yoshiko, Motomura, Masakatsu, Yoshikawa, Hiroaki, Nakamura, Yosikazu, Kawaguchi, Naoki, Onodera, Hiroshi, Araga, Shigeru, Isobe, Noriko, Nagai, Masaki, Kira, Jun-ichi
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age of Onset; Aged; Aging - physiology; Asian Continental Ancestry Group - genetics; Biological and medical sciences; Child; Child, Preschool; Comorbidity - trends; Diseases of striated muscles. Neuromuscular diseases; Epidemiology; Female; Generalized additive model (GAM); Genetic Heterogeneity; Humans; Infant; Infant, Newborn; Infantile-onset; Japan - epidemiology; Male; Medical sciences; Middle Aged; Myasthenia gravis; Myasthenia Gravis - epidemiology; Myasthenia Gravis - ethnology; Myasthenia Gravis - genetics; Nationwide survey; Neurology; Onset-age; Prevalence; Thymoma; Young Adult
• ISSN: 0022-510X; 1878-5883
• DOI: 10.1016/j.jns.2011.03.004

Abstract Objective To clarify the prevalence and clinical characteristics of myasthenia gravis (MG) in Japan. Methods We performed a nationwide epidemiological survey of MG in Japan. The clinical features were compared among five groups of patients, divided according to onset age. A generalized additive model (GAM) was used to assess the linearity of these relationships. Results A total of 8542 patients were reported, and detailed data were analyzed for 3141 patients. The estimated number of MG patients in Japan was 15,100, giving a prevalence of 11.8 per 100,000. Elderly-onset MG (≥ 65 years) accounted for 7.3% in 1987 (adjusted for population in 2005), but this had increased to 16.8% in 2006. Infantile-onset MG (0–4 years) accounted for 10.1% in 1987, and was still as high as 7.0% in 2006. The rate of ocular MG was highest (80.6%) in infantile-onset and lowest (26.4%) in early-onset disease, but the rate rose again in the late-onset group. GAM analysis of the ocular form showed a U-shaped curve, with a dip in the 20s. Anti-acetylcholine receptor antibodies were positive in only 50% of infantile-onset, but nearly 90% of elderly-onset patients. GAM analyses assessing the concurrence of thymoma and hyperplasia both showed reversed U-shapes, with peaks in the 50s and 20s–40s, respectively. Conclusions Persistent high incidence of infantile-onset disease and clinical heterogeneity according to onset age are characteristic features of MG in Japan.