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| Myasthenia Gravis Clinical Snapshot |
Q: What is the definition of Myasthenia Gravis?
A: It is a chronic autoimmune disease of the neuromuscular junction.
Q: What is the hallmark characteristic of muscle weakness in Myasthenia Gravis?
A: The weakness increases with activity and improves with rest.
Q: The muscle weakness in Myasthenia Gravis mainly affects which type of muscles?
A: Voluntary skeletal muscles.
Q: What is the status of sensation and reflexes in Myasthenia Gravis?
A: Sensation remains normal and reflexes are preserved.
Q: Which two demographic groups are commonly affected by Myasthenia Gravis?
A: Young females and older males.
Q: Myasthenia Gravis is often associated with other autoimmune diseases, particularly disorders of which gland?
A: The thyroid gland.
Q: Myasthenia gravis is caused by autoantibodies against the _____ membrane at the neuromuscular junction.
A: Postsynaptic
Q: What are the most common autoantibodies found in patients with Myasthenia Gravis?
A: Anti-acetylcholine receptor antibodies.
Q: If anti-acetylcholine receptor antibodies are negative, which other antibodies may be present?
A: Anti-MuSK antibodies.
Q: How do autoantibodies in Myasthenia Gravis lead to muscle weakness?
A: They reduce the number of functional acetylcholine receptors and damage the postsynaptic folds.
Q: In Myasthenia Gravis, the _____ is too small to trigger muscle contraction, especially after repeated use.
A: End plate potential
Q: What is the key clinical feature explained by the reduced end plate potential?
A: Fatigability.
Q: Which organ plays a central role in the pathogenesis of Myasthenia Gravis?
A: The thymus.
Q: What are the two most common thymic abnormalities seen?
A: Thymic hyperplasia and thymoma.
Q: Why is the thymus implicated in autoantibody production?
A: It contains cells that resemble muscle cells and express acetylcholine receptors.
Q: What surgical procedure is an important treatment option due to the thymus's role?
A: Thymectomy.
Q: How does muscle weakness typically change throughout the day?
A: It worsens at the end of the day and improves after rest.
Q: What are the most common initial symptoms?
A: Ocular symptoms, such as ptosis and diplopia.
Q: What is the medical term for drooping of the eyelid?
A: Ptosis.
Q: What is the medical term for double vision?
A: Diplopia.
Q: What is the status of pupillary reactions?
A: Pupillary reactions are normal.
Q: Which muscle group causes slurred speech, nasal voice, and difficulty chewing/swallowing?
A: Bulbar muscles.
Q: What is a classic feature related to eating?
A: Jaw fatigue while eating.
Q: Which part of the limbs is more affected by weakness?
A: Proximal muscles.
Q: Weakness of neck flexor muscles can lead to what clinical sign?
A: Head drop.
Q: What life-threatening emergency can occur due to severe respiratory muscle weakness?
A: Myasthenic crisis.
Q: Define myasthenic crisis.
A: Severe muscle weakness leading to respiratory failure.
Q: Name three common triggers of a myasthenic crisis.
A: Infection, surgery, pregnancy, and certain drugs.
Q: What are the two main treatments for myasthenic crisis besides ICU support?
A: Plasma exchange or intravenous immunoglobulin (IVIG).
Q: Besides clinical features, which antibodies confirm the diagnosis?
A: Anti-acetylcholine receptor antibodies or anti-MuSK antibodies.
Q: What imaging study is done for all patients and why?
A: CT scan of the chest to assess the thymus for hyperplasia or thymoma.
Q: How does weakness in Lambert-Eaton myasthenic syndrome differ?
A: Weakness improves with activity, unlike in Myasthenia Gravis.
Q: What is the first-line symptomatic treatment?
A: Pyridostigmine.
Q: How does pyridostigmine work?
A: It is an acetylcholinesterase inhibitor that increases acetylcholine at the neuromuscular junction.
Q: Name three common side effects of acetylcholinesterase inhibitors.
A: Diarrhea, abdominal cramps, and increased salivation.
Q: What is the goal of immunosuppressive therapy like corticosteroids and azathioprine?
A: To reduce autoantibody production.
Q: Thymectomy is indicated in all patients with a thymoma and also beneficial in generalized Myasthenia Gravis even _____ a thymoma.
A: Without
Q: Name three classes of drugs that worsen symptoms.
A: Aminoglycosides, fluoroquinolones, and beta blockers.
Q: What is the general prognosis with proper treatment?
A: Good; many patients achieve remission.
Q: Early in the disease, is muscle wasting prominent?
A: No, early in the disease, there is no muscle wasting.