[Myasthenia gravis in children: clinical study of 77 patients]

To study the clinical characteristics of myasthenia gravis (MG) in children and the changes in AchR-Ab-seronegative (SNMG) MG and AchR-Ab-seropositive MG (SPMG) patients.

The study was done on 77 MG patients who were diagnosed at The Pediatric Hospital, Fudan University from 1992 to 2002. This clinical trial was a non-randomized, controlled open study.

(1) The age of onset ranged from 3 months to 16 years, and the most common ages of onset were before 3 years; 32 cases were males and 45 females. The extraocular muscles were more 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 anti-acetylcholine receptor antibodies (AchRab) and 16 of 55 cases (31%) were positive for acetylcholine premembrane receptor antibody (PremRab) on the initial examination. The clinical state of the patient during the examination did not show any clear correlation with the level of these antibodies. There was no significant difference between clinical type and AchRab positive rate among the three groups. Two of 18 patients (11%) were positive for thymoma associated antibody (Tintinab). The serological test on follow-up showed that 6 of 10 SNMG cases (60%) turned to be SPMG. In 85% of the cases the results of CD cells examination was abnormal, most of them showed reduced levels of CD4(+) or CD3(+) and CD8(+). (3) The thymus proliferation was found in 22 patients (42%) by CT and changes of thymoma were found in 2 cases (4%) and were confirmed by operation. (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.

MG in our children's hospital has increased, the age of onset became younger, and type II MG cases increased. Seronegative patients could turn positive, so monitoring the patient's serology is helpful for finding more SPMG cases. Steroids have been proven effective and safe in treatment of MG in children. Patients in methylprednisolone group experienced less side effects of steroid therapy than group treated with oral prednisone.