Seventeen-year-old Lisa Montague practiced piano for 3–4 hours each day while preparing for music college auditions

Question

Some of her pieces required sustained arm-muscle activity and she began to find them hard to play, even though she had previously played them easily. When she also started to have difficulty swallowing and chewing, she told her mother, who took her to the emergency room, where the physician noticed drooping eyelids and limitation of ocular motility. An electromyogram detected impaired nerve-to-muscle transmission. Administration of pyridostigmine rapidly improved Lisa's symptoms. Which of the following blood-test results would be most consistent with her condition?
a. elevated rheumatoid factor
b. elevated anti-myelin basic protein antibodies
c. elevated anti-acetylcholine receptor antibodies
d. elevated anti-nuclear antibodies
e. elevated anti-Rh antibodies.

Answer 1

Rationale: The correct answer is c. This is a case of myasthenia gravis, a type II autoimmune disease caused by antagonist antibodies against acetylcholine receptors, which impede the binding of the neurotransmitter acetylcholine. Lisa experienced muscle weakness and impairment of neuromuscular signaling, which affected the strength in oral, ocular, and upper extremity muscles, hallmarks of this disease. Pyridostigmine is an inhibitor of cholinesterase, an enzyme that normally degrades acetylcholine after neuromuscular transmission. That Lisa demonstrated rapid recovery when treated with this drug shows that acetylcholine was associated with her symptoms, and by increasing the acetylcholine concentration her symptoms were alleviated.