Retrospective evaluation of clinical and laboratory results of childhood myasthenia gravis patients

Juvenile myasthenia (JM) is an autoimmune disorder of the neuromuscular junction caused by autoantibodies against acetylcholine receptors (AChR) and muscle-specific kinase (MuSK). Pediatricians' knowledge about the characteristics of JM is important for diagnosis and differential diagnosis.We reviewed our cases of JM (n=50) for their age of onset, sex, presenting symptoms, antibody profile, electrophysiological evaluation and response to treatment. Median age at onset was 107.8 (24-180) months. Cases clustered in two age groups: boys under age 10 and girls over age 15 years. Male/female ratio was 1.4: 1 in patients <10 years and 1: 1.4 in those >10 years. Muscle weakness was affecting extraocular muscles only in 26 patients (52%), ocular and bulbar muscles in 7 patients (14%) and generalized weakness was observed in 17 patients (34%). AChR antibodies were measured in 48 patients (96%) of whom 27 (56.2%) were positive. Anti-MuSK antibodies, tested in 12 patients, returned positive in 6 (50%) patients. Electromyography was performed in 31 patients (62%) and showed diagnostic findings in 25 (80.6%). Of 10 patients who underwent thymectomy, 8 had thymic hyperplasia, 1 had atrophy, 1 patient had a thymic cyst. All patients received anticholinesterase therapy. Treatment response was best in boys and purely ocular JM patients. Steroids were given to patients with ocular-bulbar involvement and in the puberty age group. Other treatment modalities were intravenous immunoglobulin in 10 patients and plasmapheresis in 2 patients. This series shows paraclinical tests usually contribute to the diagnosis of JM, with at least one test being positive. Anticholinesterase medications and steroid were effective in the majority of JM patients. No patient went into myasthenic crisis or refractory disease. Physicians' awareness of the course of JM is important for their management of JM cases as well as delivering appropriate information to patients and parents. Key words: Juvenile Myasthenia, acetylcholine receptor, muscle-specific kinase