P-NJ005. Clinical profile and outcome of childhood-onset Myasthenia gravis

Introduction. Myasthenia gravis (MG) is an autoimmune disease with peak incidence in fourth decade. Childhood-onset MG is uncommon. We aim to describe the clinical profile and outcome of childhood-onset MG. Methods. Retrospective chart review of 27 patients (M:F 13:14) with childhood-onset MG seen in a single neurology unit between 2000 and 2019. Diagnosis was established by decremental response in repetitive nerve stimulation, response to neostigmine, and/or antibody positivity. Congenital Myasthenic syndromes were excluded. Results. Demographic and clinical features included: mean onset-age of 12.81±4.63 years, mean symptom-duration of 23.63±36.49 months, ptosis (100%), ophthalmoplegia (63%), facial weakness (55.55%), chewing difficulty (40.74%), dysphagia (48.14%), dysarthria (14.81%), neck weakness (25.92%), shoulder-girdle weakness (44.44%), pelvic-girdle weakness (48.14%), and respiratory weakness (14.81%). Myasthenia Gravis Foundation of America (MGFA) grade at first evaluation was I (n = 11), IIa (n = 7), IIb (n = 2), IIIa (n = 4), IIIb (n = 2), and IVb (n = 1). Two patients developed myasthenic crisis during course of illness. Associated illnesses included seizure disorder (n = 2), diabetes (n = 1), hypothyroidism (n = 1), and psychiatric illnesses (n = 4). Acetylcholine receptor antibody was positive in 12 patients while MuSK was positive in one patient. Chest computed tomography (CT) showed thymic hyperplasia in 12 patients and was normal in 6 patients. Thymectomy was performed in 9 patients (hyperplasia in 7, normal histology in 2). Time from MG onset to initiation of pyridostigmine was 13.80 ± 27.83 months and mean maximum dose of pyridostigmine was 172.22 ± 127.50 mg/day. Immunosuppressants administered in 22 patients included intravenous immunoglobulin (n = 3), plasma exchange (n = 5), steroids (n = 22), azathioprine (n = 4), mycophenolate (n = 2), methotrexate (n = 3), cyclophosphamide (n = 2), and rituximab (n = 1). Of 20 patients with follow- up details, remission was achieved in 17, of which 12 could stop pyridostigmine. Conclusion. In our cohort, majority had mild-moderate MG and myasthenic crises were uncommon. Treatment response was good. Remission was achieved in majority and in many of them, pyridostigmine was discontinued.