[P3-145] Plasma exchange was very effective in a child with anti-muscle-specific kinase positive myasthenia gravis
We report the case of a 12-year-old girl with muscle-specific kinase autoimmune myasthenia gravis (MuSK MG). She suffered from headaches and a movement disorder of both eyes when she was 12 years and 8 months old. Her headache and eye movement disorder spontaneously improved after two weeks. After three months, the headache and eye movement disorder reappeared. After that, she exhibited ptosis, dysphagia and weakness of facial muscles. She visited our hospital when she was 12 years and 11 months old. We considered that she suffered from MG, but an edrophonium test was negative, and we did not find any fluctuations in muscle strength during the day. Subsequently, the fluctuating symptoms became clear, and a second edrophonium test was positive. The muscle-specific kinase autoantibody was positive. Therefore, we diagnosed her with anti-MuSK positive MG. We initially treated her with methylpredonisone pulse therapy. However, her symptoms persisted. Then, she underwent five sessions of plasma exchange. The treatment was very effective, and all of her symptoms disappeared. Currently, she is being treated with oral steroids and tacrolimus. She has maintained complete stable remission status after plasma exchange. Plasma exchange and aggressive immune-suppression therapy might be more effective for childhood-onset anti-MuSK positive MG.