Flashcards in Exam 3 -- Myasthenia Gravis Deck (17):
What is the hallmark of myasthenia gravis?
Fluctuating weakness of skeletal muscles.
Describe the age and gender of the typical MG patient.
There is a bimodal distribution: younger females (teens-20s) and older males (50-70)
True or false: more than 50% of patients with MG present with ocular symptoms, and 50% of these will develop generalized MG within 2 years.
What percent of patients with generalized MG have autoantibodies against the acetylcholine receptor?
What percent of seronegative (for autoantibodies against AChR) patients with generalized MG have autoantibodies against the receptor tyrosine kinase?
What percent of patients with MG have an abnormality of the thymus? What percent have a thymoma?
60-70% = abnormal thymus; 10-12% have a thymoma.
MG can be exacerbated by medications. Which medications or classes of medications can do this?
Antibiotics (especially gentamycin, tobramycin, telithromycin), fluoroquinolones, hydroxychloroquine, botulinum toxin, penicillamine, beta blockers, anesthetics, and high dose steroids.
Holding an ice pack over the ptotic eye of a patient with MG should ___________ (improve/worsen) the ptosis.
A patient with ptosis due to myasthenia gravis, when looking into primary gaze from a downgaze position, might experience which phenomenon?
Cogan's lid twich
What drug is used in the diagnosis of MG? What class of drug is this, and what is its antidote?
Edrophonium; class is acetylcholinesterase inhibitor; atropine is the antidote.
In terms of electrodiagnostic testing for MG, repeated nerve stimulation in a patient with MG shows reduced amplitude. This is positive in more than 75% of patients with generalized MG. Single fiber stimulation is even better at 80-95% and is better for ocular MG.
Fill in the blank: _____________, an anticholinesterase agent used to treat acute MG, is usually dosed at qid due to its duration of 3-4 hours.
Chronic immunomodulators for MG include azathioprine, mycophenolate, cyclosporine, tacrolimus, and prednisone. What kind of dose would you use with prednisone, and why?
Low dose (no more than 1.0 mg/kg), since high dose steroids can make MG worse.
In which two situations would you use intravenous immunoglobulin for MG?
During a myasthenic crisis or prior to a thymectomy.
True or false: a thymectomy is recommended in almost all patients who are positive for autoantibodies against the acetylcholine receptor, and makes the chances of a medication-free remission twice as likely.
A myasthenic crisis is respiratory failure due to weakness of the respiratory muscles, and can occur after thymectomy. At what point during the course of the disease does this usually occur? How many MG patients experience it?
Usually occurs in the first years after diagnosis; 10-20% of patients experience it at some point.