What is myasthenia gravis (Myasthenia Gravis)?

From the Guidelines

Myasthenia gravis is an autoimmune neuromuscular disorder characterized by weakness and rapid fatigue of voluntary muscles, which can be managed with acetylcholinesterase inhibitors, immunosuppressive medications, and other treatments as needed. This condition occurs when the immune system mistakenly attacks the communication point between nerves and muscles, specifically targeting acetylcholine receptors at the neuromuscular junction, as described in the study by 1. The disruption prevents nerve signals from properly triggering muscle contractions, leading to common symptoms such as drooping eyelids, double vision, difficulty swallowing or speaking, and weakness in the arms and legs that typically worsens with activity and improves with rest.

Key Characteristics and Symptoms

• Weakness and rapid fatigue of voluntary muscles
• Drooping eyelids (ptosis)
• Double vision (diplopia)
• Difficulty swallowing or speaking
• Weakness in the arms and legs that worsens with activity and improves with rest
• Ocular myasthenia gravis affects only the levator, orbicularis oculi, and the extraocular muscles, as noted in the study by 1

Treatment Options

• Acetylcholinesterase inhibitors like pyridostigmine (Mestinon), typically starting at 30-60mg three to four times daily, which improve neuromuscular transmission by increasing available acetylcholine, as recommended in the study by 1
• Immunosuppressive medications such as prednisone (often starting at 20mg daily and gradually increasing), azathioprine, or mycophenolate mofetil may be used to reduce the immune attack
• In crisis situations, treatments like plasma exchange or intravenous immunoglobulin (IVIG) can provide rapid improvement, as suggested in the study by 1
• Some patients benefit from thymectomy (surgical removal of the thymus gland) as the thymus often plays a role in the abnormal immune response
• Regular monitoring by a neurologist is essential as medication dosages often need adjustment based on symptom severity and response to treatment, as emphasized in the study by 1

Important Considerations

• Avoid medications that can worsen myasthenia, such as β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides, as warned in the study by 1
• ICPi-associated myasthenia gravis may be monophasic; therefore, additional corticosteroid-sparing agents may not be required, as noted in the study by 1

From the Research

Definition and Characteristics of Myasthenia Gravis

• Myasthenia gravis is an antibody-mediated disorder of neuromuscular transmission characterized by weakness and fatigue of voluntary muscles 2.
• It is a rare autoimmune disease that causes debilitating muscle weakness due to impaired neuromuscular transmission 3.
• The disease may affect persons of all ages, but especially women aged 20 to 40 years 4.
• Myasthenia gravis is characterized by fluctuating muscle weakness and fatigue of different muscle groups, with the ocular, facial, and bulbar muscles most often involved 4.

Clinical Features and Diagnosis

• The muscular disorder is generalized in 85% and confined to extraocular muscles in 15% of patients 5.
• The disease is graded based on pattern and severity of muscular involvement 5.
• Diagnostic evaluation consists of bedside assessment, antibody testing, and electrophysiologic studies 2.
• Diagnostic tests include use of anticholinesterase agents (tensilon test), curare test, repetitive nerve stimulation, Ach-R antibody assay, and single fiber electromyography 5.

Treatment Options

• Various therapeutic options are available, including anticholinesterase inhibitors for symptomatic management, immunosuppressive agents as maintenance therapy, and thymectomy 2.
• Plasmapheresis and intravenous immunoglobulin are used in patients in crisis or those with rapidly worsening or refractory symptoms 2, 6.
• New strategies have been proposed for the treatment of myasthenia gravis, including complement blockade and neonatal Fc receptor antagonism 3.
• Treatment may include anticholinesterase drugs, corticosteroids, plasmapheresis, immunoglobulin, immunosuppressive drugs, and thymectomy 4.