The patient is a 16-year-old girl recently diagnosed with myasthenia gravis, class IIa. She complains of diplopia and weakness affecting in her upper extremities. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She is on acetylcholinesterase inhibitor treatment combined with immunosuppressants. But she still has some symptoms. She does not smoke or use illicit drugs. She is not sexually active, and her menses are regular. Her physical exam and lab studies are not remarkable for any other abnormalities.
BP: 110/75
Hgb: 11 g/dl
WBC: 8000 /mm3
Plt: 300000 /ml
Creatinine: 0.5 mg/dl
BUN: 10 mg/dl
Beta hcg: negative for pregnancy