Myasthenia gravis in Hong Kong Chinese. 2. Paediatric disease.

In a study covering 85% of the population of Hong Kong, 39% of all myasthenia gravis (MG) patients, i.e. 103 individuals (54 girls and 49 boys) were found to have had MG with onset before puberty. Two patients had transient neonatal MG, 20 had early onset juvenile MG and 81 had late onset juvenile MG. Restricted ocular MG occurred in 71% of patients and the remainder had generalised MG. The median age at onset was 4 years. Complete remission occurred in 34 patients (34%), a good response in 14 (14%), and fair response in 32 (32%). The clinical course remained static in 16 patients (16%) and 3 patients deteriorated. Two patients died, 1 with myasthenic crisis and the other with cholinergic crisis. All patients, except 2 with neonatal MG, were initially treated with anticholinesterase, but 24% also required steroid therapy. Thymectomy was performed for 12 patients, of whom 5 (42%) showed marked improvement. Thymic histology was normal in 3, showed hyperplasia in 6, non-invasive thymoma in 1 and involution in 2. The most commonly associated disease was Graves' disease which occurred in 7 patients (7%).