Nokea
A 38-year-old female presents with muscle fatigue that is worse by the end of the day. She reports to have myalgias in the back of her neck, and at times her head "drops." She also states to sees "double" when watching television, or reading for a prolonged period of time. On physical examination, ptosis is produced when asking the patient to look at the ceiling without blinking. Pupillary function is intact. Appropriate serologic testing is obtained. On repetitive nerve stimulation, the amplitude of the compound muscle action potential progressively declines. Which of the following is most likely the diagnosis?
Correct Answer: D
Rationale: The patient's symptoms of fatigable weakness, ptosis, and diplopia, along with the decremental response on repetitive nerve stimulation, are classic for myasthenia gravis. This autoimmune disorder is caused by antibodies against acetylcholine receptors at the neuromuscular junction, leading to impaired muscle contraction. Botulism and Lambert-Eaton syndrome also cause weakness but have different clinical and electrophysiological features. Multiple sclerosis and acute inflammatory demyelinating polyradiculopathy do not typically present with fatigable weakness.