Long-term Prognosis Of Ocular Myasthenia Gravis In Children And Analysis Of Its Related Factors

ObjectiveMyasthenia gravis (MG) is an autoimmune disease caused by disorders in neuromuscular junction (NMJ).There are three subtypes of myasthenia gravis in children, including congenital myasthenia gravis, neonatal myasthenia gravis and juvenile myasthenia gravis (JMG), of which juvenile myasthenia gravis is the most common subtype,accounting for 11%～29%.According to its clinical characteristics, juvenile myasthenia gravis is divided into ocular myasthenia gravis (OMG), stem myasthenia gravis and generalized myasthenia gravis. OMG is the most common type among them.Childhood myasthenia gravis has racial and geographical differences, and it differs from adult onset myasthenia gravis in its gender prevalence, severity, aetiology and choice of treatment modalities. Currently, the long-term progrosis of OMG and its related factors are not well studied in children. So, patients aged between 2 and 14 years were selected for this follow-up survey, who were newly diagnosed with OMG at onset, to explore long-term prognosis of ocular myasthenia gravis in children and its related factors.Methods88 patients aged between 2 and 14 years (averaged 3.6 years) were selected for this follow-up survey, who were newly diagnosed with OMG at onset from 1995 to 2003 in department of pediatrics, Qilu hospital of Shandong University. There were 47 females and 41 males. The follow-up time was 5 years to 10 years. At the end of the follow-up, three standards were used in evaluating their long-term prognosis: asymptomatic,remained ocular and converted into generalized myasthenia gravis. Patients with OMG at onset were divided into two subgroups according to their prognosis:the patients whose disease became asymptomatic or remained ocular throughout the follow-up time were placed in group A, the patients who converted into generalized myasthenia gravis were placed in group B. Clinical characteristics, family history and laboratory findings were compared between the two groups.Data analysis was tested by univariate and multivariate non-conditional Logistic regression andχ2 examination with SPSS13.0. P<0.05 was accepted as the limit of significance.Result1. Long-term prognosis:At the end of follow-up,13 patients (14.77%) were asymptomatic with drugs about two years; 59 patients (67.05%) remained ocular throughout the follow-up duration, including 26 recrudescent patients after drug withdrawal; 16 patients (18.18%) converted into generalized myasthenia gravis, majority (9/16,56.25%) occurred within 1 year after onset.2. Related factors:The long-term prognosis of OMG had an sinificant correlation with acetylcholine receptor (AchR) antibody and thymopathy(including thymoma and thymic hyperplasia) (P<0.05). The postive rate of acetylcholine receptor (AchR) antibody and thymopathy in B group was higher than that in A group,the difference was significant in statistics (P<0.05).Conclusion1. This study shows some distinctive characteristics of OMG in children and the probability of converting into generalized myasthenia gravis is lower than that in adults.2. Our findings also suggest that several factors, such as the AchR antibody and thymopathy(including thymoma and thymic hyperplasia),may have an impact on the risk of developing generalized disease with OMG in children.