Prepubertal anti-Musk positive myasthenia gravis with long remission

Anti-MuSK positive myasthenia gravis (MuSK-MG) is rare prepuberty. We report a female patient with MuSK-MG starting at 3.5 years with ptosis as the sole symptom for 2 years. A brief period of generalization was followed by complete stable remission for 6 years. Prolonged ocular symptoms and long remissions are not features of MuSK-MG, but are often seen in prepubertal onset MG. The patient then presented at age 12 with moderately severe symptoms which were almost confined to oculobulbar muscles and were unresponsive to pyridostigmine. She was dependent on corticosteroids and thymectomy did not seem to be effective. She was later noted to have tongue atrophy after a period without treatment. Our patient thus presented with features seen in many prepubertal patients, but the later course was quite typical of MuSK-MG.