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Clinical Presentation and Diagnosis
    • Initial Symptoms: Fluctuating muscle weakness, especially in ocular muscles (ptosis, diplopia), with progression to generalized weakness.
    • Differential Diagnosis: Differentiate from other causes of muscle weakness, such as Lambert-Eaton myasthenic syndrome, botulism, and stroke.
    • Key Diagnostic Tests:
    • Serology: Anti-acetylcholine receptor (AChR) antibodies; anti-MuSK antibodies for AChR-negative patients.
    • Electrophysiology: Repetitive nerve stimulation and single-fiber EMG.
    • Imaging: Chest CT or MRI to rule out thymoma.
    • Bedside Tests: Ice pack test can help confirm diagnosis in ptosis.
Management and Treatment
    • First-line Treatment:
    • Acetylcholinesterase Inhibitors: Pyridostigmine for symptom management.
    • Long-term Management:
    • Immunosuppressants: Corticosteroids, azathioprine, mycophenolate mofetil, or cyclosporine.
    • Thymectomy: Recommended for thymoma and often in generalized disease.
    • Crisis Management:
    • Myasthenic Crisis: Requires intensive care, mechanical ventilation, and plasmapheresis or IVIG.
    • Cholinergic Crisis: Differentiate from myasthenic crisis; management includes discontinuing acetylcholinesterase inhibitors and supportive care.
Complications
    • Respiratory Failure: Particularly during myasthenic crisis, necessitating prompt recognition and treatment.
    • Thymoma: Associated with more severe disease; thymectomy can be curative in some cases.
Prognosis and Follow-up
    • Requires long-term management and monitoring for disease progression and treatment-related side effects.
Commonly Tested Items on Step 3
    • Crisis Management: Differentiating and managing myasthenic vs. cholinergic crisis.
    • Thymectomy: Indications and outcomes, especially in relation to thymoma.
    • Immunosuppressive Therapy: Long-term management and monitoring for side effects.
    • Complex Cases: Considerations in pregnancy, surgery, and infections that might exacerbate symptoms.

Related Terms