Myasthenia gravis in Hong Kong Chinese. 2. Paediatric disease

Abstract

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%).

PIP: Researchers analyzed retrospective data on 103 patients living in Hong Kong who experienced onset of myasthenia gravis (MG) during childhood to determine differences in clinical manifestations between them and Caucasoids and to assess their clinical management strategy. The researchers did not include data on the 2 females who had transient neonatal MG. MG presented in 20 patients between birth and 2 years of age whose mothers did not have MG (early onset juvenile MG). It appeared in 81 patients between 2 years of age and puberty (late onset juvenile MG). Peak onset was around 2-3 years of age with a second peak at around 10 years. 72 patients (71%) had restricted ocular MG while the other 29 patients had generalized MG. Basically the same percentage of Japanese childhood cases also had ocular MG. On the other hand, less than 20% of Caucasoid cases had ocular MG. The overall female-to-male sex ratio stood at 1.1:1 compared to 6:1 in North America. Males were more likely to have had ocular MG (0.8:1) while females were more likely to have had generalized MG (2.2:1). Only 5 patients with ocular MG later developed generalized MG compared to up to 35% of Caucasoid patients. They also had late onset juvenile MG. All patients received anticholinesterase. 24% of patients also received steroids compared to 4% in another study. 80% (16) of the 26 patients improved. 34 patients achieved complete remission. Treatment brought about a good response in 14 patients and a fair response in 32 patients. The condition of 16 patients neither improved nor deteriorated. 3 patients became more ill; 2 died (myasthenic crisis and cholinergic crisis). Physicians performed thymectomy in 12 patients, all of whom had late onset juvenile MG and moderately severe generalized MG. All 12 improved, 5 improved considerably. The thymus of 6 patients showed hyperplasia that patient showed; of 1 noninvasive thymoma, and that of 2 showed involution. 3 patients had a normal thymus. Graves disease was the most frequently associated diseases (7 patients).