CLINICAL AND IMMUNOLOGICAL STUDIES OF JUVENILE MYASTHENIA GRAVIS

Objectives: The purpose of this study is to evaluate the clinical characteristics and long-term changes of anti-acetylcholine receptor antibodies in patients with juvenile MG.

Methods: Retrospective data from the patients with juvenile MG in the children's Hospital, Fudan University from 1992 to 2002 were presented. In all cases, the diagnosis was confirmed by a combination of clinical examination and Neostigmine test. Information regarding mode of presentation, myasthenia classification, ocular and systemic involvement, AChRab level estimation, therapy and outcome was collected and evaluated. The serological test was followed-up.

Results: (1) 77 patients were included in the study whose were aged from 3 months to 16 years at presentation. The most common ages of onset were before 3 years. The female to male ratio was 1.4:1. The extraocular muscles were most frequently involved. According to the modified Osserman's criteria, 54 patients (70%) were classified as type I, 21 cases (27%) as type II and 2 cases (3%) as type III. (2) Eighteen of 55 cases (35%) were positive for AchRab and 16 of 55 cases (31%) were positive for acetylcholine premembrane receptor antibodies (PremRab) on the initial examination. The clinical state of the patients during the examination did not show clear correlation with the levels of these antibodies. There was no significant difference between clinical type and AchRab positive among the 3 groups. Two of 18 patients (11%) were positive for thymona associated antibody (Titinab). The serological test on follow-up showed that 6 of 10 AchRab seronegative (SNMG) cases (60%) turned to be AchRab seropositive (SPMG). (3) The thymus proliferation was found in 22 patients (42%) by CT and thymoma were found and confirmed by operation in 2 cases (4%). (4) In 50% of the cases the electromyography (EMG) was abnormal. (5) After anticholinesterase drugs and steroids treatment the prognosis of patients with MG was usually good.

Conclusion: We observe an increase in the incidence of juvenile MG in our hospital. The age of onset become younger, and type II cases were likely to increase. AchRab serogegative patients could turn to be positive. The Serology monitoring is helpful for finding more AchRab seropositive cases. Steroids have been proven effective and safe in treatment of juvenile myasthenia gravis. Patients treated with methylprednisolone experienced less side effects of steroid therapy than being treated with oral predisone.