What is myasthenia gravis (Myasthenia Gravis, MG)?

From the Guidelines

Myasthenia gravis is a B-cell mediated autoimmune disorder that affects the neuromuscular junction, causing variable weakness exacerbated by fatigue, and can be characterized by ocular, bulbar, limb, and respiratory muscle involvement. 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 symptoms of myasthenia gravis can include 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

• The term myasthenia gravis refers to a group of autoimmune disorders that profoundly affect activity at the neuromuscular junction, as noted in the study by 1.
• Myasthenia gravis can be generalized, affecting large motor groups and sometimes including ocular features, or it can be ocular, affecting only the levator, orbicularis oculi, and the extraocular muscles, as described in the study by 1.
• The incidence of myasthenia gravis ranges from 0.04 to 5/100,000 per year, and prevalence estimates are 0.5 to 12.5/100,000 per year, according to the study by 1.
• There is an increased risk for myasthenia gravis in the presence of autoimmune thyroid disease and thymoma, as noted in the study by 1.

Treatment and Management

• Treatment options for myasthenia gravis include acetylcholinesterase inhibitors like pyridostigmine (Mestinon), which improve neuromuscular transmission by increasing available acetylcholine, as described in the study by 1.
• Immunosuppressive medications such as prednisone, azathioprine, or mycophenolate mofetil may be added to reduce the autoimmune response, as noted in the study by 1.
• In crisis situations, treatments like plasma exchange or intravenous immunoglobulin (IVIG) can provide rapid improvement, as described in the study by 1.
• Some patients may benefit from thymectomy (surgical removal of the thymus gland) as the thymus often plays a role in the disease process, as noted in the study by 1.
• Regular monitoring by a neurologist is essential as symptoms can fluctuate, and medication dosages often require adjustment based on symptom severity and time of day.

From the FDA Drug Label

Myasthenic crisis due to an increase in the severity of the disease is also accompanied by extreme muscle weakness, and thus may be difficult to distinguish from cholinergic crisis on a symptomatic basis For detailed information on the management of patients with myasthenia gravis, the physician is referred to one of the excellent reviews such as those by Osserman and Genkins2, Grob3 or Schwab4,5. Myasthenia gravis is a disease characterized by increasing muscle weakness.

• The provided text does not give a detailed description of the disease.
• Myasthenic crisis is a state of extreme muscle weakness due to an increase in the severity of myasthenia gravis 2.

From the Research

Definition and Characteristics of Myasthenia Gravis

• Myasthenia gravis (MG) is an autoimmune disease characterized by dysfunction of the neuromuscular junction, resulting in skeletal muscle weakness 3.
• It is equally prevalent in males and females, but debuts at a younger age in females and at an older age in males 3.
• The most common symptoms include ptosis, diplopia, facial bulbar weakness, and limb weakness 3, 4.

Classification and Diagnosis

• MG can be classified based on the presence of serum autoantibodies, including acetylcholine receptor (AChR) antibodies, muscle-specific kinase (MuSK) antibodies, and low-density lipoprotein receptor-related protein 4 (Lrp4) antibodies 3.
• Approximately 10% of patients are seronegative for antibodies binding the known disease-related antigens 3.
• Diagnosis can be established with additional tests, including repetitive nerve stimulation, single fiber EMG, and the ice pack test 3.

Treatment Options

• Treatment options for MG consist of symptomatic treatment (such as pyridostigmine), immunosuppressive treatment, or thymectomy 3, 5, 6.
• Pyridostigmine is a commonly used acetylcholinesterase inhibitor for symptomatic treatment, and is generally considered safe 5.
• Immunotherapy, including corticosteroids and azathioprine, is often used for long-term disease management 7, 6.