A Case Report of Juvenile Myasthenia Gravis; Misdiagnosis and Considerations

Juvenile myasthenia gravis (JMG) is a rare autoimmune disease acquired in childhood, comprising 8%-15% of all myasthenia gravis cases depending on geographic and ethnic populations. Ocular myasthenia gravis presents as ptosis with extraocular movement restriction and is frequently misdiagnosed as third nerve palsy or congenital ptosis when bilateral. Early diagnosis prevents disease progression and unnecessary interventions. We report a case of JMG initially misdiagnosed as Guillain-Barré syndrome (GBS) to highlight diagnostic pitfalls. A 4-year-old girl presented with left eye ptosis, followed by bilateral ptosis after 2 days, then gait disorder and inability to stand after 5 days. She had a previous admission 2 months earlier with severe respiratory distress, for which she received intravenous immunoglobulin (IVIG) under the suspicion of GBS. In the current admission, bilateral ptosis was evident, and repetitive nerve stimulation (RNS) showed a decremental response of > 10%, consistent with myasthenia gravis. Anti-acetylcholine receptor (AChR) antibody was positive. She was treated with pyridostigmine (5 mg/kg/day) and showed good response. JMG should be considered in the differential diagnosis of acute muscle weakness with cranial nerve involvement, even when respiratory failure dominates, and normal cerebrospinal fluid protein in suspected GBS should prompt re-evaluation.