title: [The clinical characteristics of early-onset versus late-onset types of myasthenia gravis].
abstract: OBJECTIVE
  To compare the clinical characteristics of early-onset and late-onset myasthenia gravis (MG).
  
  
  METHODS
  A total of 819 MG patients admitted in our department during the same period were reviewed retrospectively. The patients with MG were divided into two groups by the age of onset, which were the early-onset MG (< 49 years) and late-onset MG (≥ 50 years). Several clinical features were compared in the two groups including the percentage, initial symptoms, MG types, the positive rates of neostigmine test and repetitive nerve stimulation, thyroid function and thymic abnormalities.
  
  
  RESULTS
  The more common onset age of MG was 0 - 49 years (early-onset). In both groups the male and female ratio was closer to 1:1 with the extra ocular muscles weakness presented as the most frequent symptom and Type IIB presented as the most common type in both groups (41.51% and 51.37% respectively in early-onset and late-onset groups). Type I was more common in early-onset group while type IIB was more common in late-onset group (P < 0.05). There was no significant difference in the positive rates of neostigmine test and repetitive nerve stimulation between the two groups. The thyroid function abnormality ratio was higher in early-onset group. Hyperplastic thymus was common in early-onset group (67.57%) while both hyperplastic thymus and thymoma were common in late-onset group (48.68% and 47.37%).
  
  
  CONCLUSIONS
  The clinical characteristics of early-onset and late-onset myasthenia gravis (MG) was different in MG type, the positive rate of thyroid function abnormalities and thymic pathologic type.
authors.affiliation: Department of Neurology, Center for Myasthenia Gravis, Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Chen
authors.forename: Dong-Ning
authors.initials: DN
authors.lastname: Wei
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000145:classification / Q000175:diagnosis; D012189:Retrospective Studies; D055815:Young Adult