Myasthenia gravis in children: a longitudinal study.

Background: Juvenile myasthenia gravis (JMG) is an uncommon disease. Unlike adults, clinical characteristics and outcomes of myasthenia gravis (MG) are not well studied in children.
Patients and Methods: Case records of 77 patients with MG who were 15 years of age or less at disease onset, evaluated over a period of 34 years at the National Institute of Mental Health and Neurosciences, Bangalore, India, were reviewed. Their clinical characteristics and response to therapy was compared with 290 patients with MG onset after 15 years of age.
Results: Median age at onset was 8 years and mean period of follow-up was 6.2 years (range 6 months to 25 years). At presentation, 30% of patients had ocular myasthenia and the rest had generalized disease. Twenty-one patients (27%) had disease confined to ocular muscles throughout the course and three had limb girdle myasthenia. Familial myasthenia was more common than adult onset disease, 10 patients had positive family history. Unlike adults, none of the patients had associated autoimmune disease. Fifty-two patients (67%) received corticosteroids, and azathioprine was added in five patients. Thymectomy was performed in 11 patients, six below the age of 15 years. Thymic histology was normal in one and showed hyperplasia in eight and thymoma in one. Four patients had crisis. At the end of follow-up, 25 patients were asymptomatic, 28 had partial improvement, and nine remained unchanged or worsened and two died. Ten patients achieved complete stable remission.
Conclusions: This study shows some distinctive characteristics of JMG, such as higher frequency of ocular myasthenia, benign course, better long-term outcome and lack of association of thymoma and other autoimmune disorders.