Myasthenia gravis Flashcards
What is myasthenia gravis?
Myasthenia gravis is an autoimmune disorder resulting in insufficient functioning acetylcholine receptors.
What percentage of myasthenia gravis cases have antibodies to acetylcholine receptors?
Antibodies to acetylcholine receptors are seen in 85-90% of cases.
What is the gender prevalence of myasthenia gravis?
Myasthenia gravis is more common in women with a ratio of 2:1.
What is the key feature of myasthenia gravis?
The key feature is muscle fatigability, where muscles become progressively weaker during periods of activity and slowly improve after periods of rest.
What are some symptoms of myasthenia gravis?
Symptoms include extraocular muscle weakness (diplopia), proximal muscle weakness (face, neck, limb girdle), ptosis, and dysphagia.
What percentage of myasthenia gravis patients have thymomas?
Thymomas are found in 15% of myasthenia gravis patients.
What autoimmune disorders are associated with myasthenia gravis?
Associated autoimmune disorders include pernicious anemia, autoimmune thyroid disorders, rheumatoid arthritis, and systemic lupus erythematosus (SLE).
What percentage of myasthenia gravis patients have thymic hyperplasia?
Thymic hyperplasia is seen in 50-70% of myasthenia gravis patients.
What is the most sensitive investigation for myasthenia gravis?
Single fibre electromyography has a high sensitivity of 92-100%.
What imaging is used to exclude thymoma in myasthenia gravis?
CT thorax is used to exclude thymoma.
What is the typical CK level in myasthenia gravis?
CK levels are typically normal in myasthenia gravis.
What antibodies are tested in myasthenia gravis?
Antibodies to acetylcholine receptors are positive in around 85-90% of patients; about 40% of remaining patients are positive for anti-muscle-specific tyrosine kinase antibodies.
What is the Tensilon test?
The Tensilon test involves IV edrophonium, which temporarily reduces muscle weakness, but is not commonly used anymore due to the risk of cardiac arrhythmia.
What is the first-line treatment for myasthenia gravis?
Pyridostigmine is the first-line treatment, which is a long-acting acetylcholinesterase inhibitor.
What immunosuppressive treatments may be used in myasthenia gravis?
Immunosuppression may include prednisolone initially, and azathioprine, cyclosporine, or mycophenolate mofetil may also be used.
What surgical procedure may be performed for myasthenia gravis?
Thymectomy may be performed as part of the management.
What is the management for myasthenic crisis?
Management includes plasmapheresis and intravenous immunoglobulins.
Are antibodies less commonly seen in ocular myasthenia gravis?
Yes, antibodies are less commonly seen in disease limited to the ocular muscles.
What is the most common exacerbating factor of myasthenia gravis?
Exertion resulting in fatigability, which is the hallmark feature of myasthenia gravis. Symptoms become more marked during the day.
Which drugs may exacerbate myasthenia gravis?
The following drugs may exacerbate myasthenia: penicillamine, quinidine, procainamide, beta-blockers, lithium, phenytoin, and certain antibiotics (gentamicin, macrolides, quinolones, tetracyclines).
