Myasthenia gravis in Chinese children.

A clinical study of 50 Southern Chinese myasthenic children observed for periods of two to 18 years (six years on average) revealed manifestations different from those of caucasian patients. Onset was early, at an average of 4.8 years. 82 per cent had ocular myasthenia. Ophthalmoplegia followed ptosis between three months and 10 years later. Additional facial and isolated limb-muscle fatigability developed in only 6 per cent within three months to 3 1/2 years. Only 12 per cent developed generalized myasthenia. Although extension from ocular to the generalized form did not occur later than 20 months after onset, a deterioration in ocular symptoms, without extension into generalized myasthenia, occurred in nine of 18 children during adolescence. Ptosis and generalized myasthenia responded better to anticholinesterase and/or prednisone. Ophthalmoplegia was difficult to treat. The natural clinical course was benign. Spontaneous remission occurred in 62 per cent of cases, but 54.8 per cent of these relapsed, all confined to ocular muscles. Although there was no familial occurrence of myasthenia gravis, an association was found between myasthenia and thyroid disorders in some patients and their relatives. The association with HLA BW46 antigen was striking. Acetylcholine receptor antibodies were absent in the majority, but mildly elevated titres were found in three of five patients whose ocular symptoms deteriorated during adolescence, without extension into generalized myasthenia.