The Correct Answer is A!

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A 34-year-old woman presents with a three month history of generalized fatigue, proximal weakness without pain, ptosis, and binocular diplopia, all worse in the evenings and after activity. Her CK level and reflexes are normal.

What's the most likely explanation?

  1. Myasthenia gravis
  2. Fibromyalgia
  3. Polymyositis
  4. Hypothyroidism


This is a typical story for myasthenia gravis. So sometimes fibromyalgia will mimic it. Those patients typically have pain of course. Polymyositis will have an elevated CK with proximal weakness. Ptosis is less likely. Hypothyroidism could definitely mimic this. Always check the TSH. Hypothyroidism will also cause a rise in the CK in somebody who really has myxedema with myopathy. And then CIDP will present with proximal weakness. That's a neuropathy, but the hallmark is really a motor predominant, often proximal and also distal weakness with areflexia or reduced reflexes.

1.  Source: "Comparative Analysis of Pre/Post Assessments of Live/Didactic Course Attendees when compared to Mico-Learning/Online Course Users., "Knowledge to Practice, 2017.