Summary about Disease
Myasthenia Gravis (MG) is a chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles, which are responsible for breathing and moving parts of the body. It is characterized by fluctuating muscle weakness that worsens after periods of activity and improves after periods of rest. MG occurs when the normal communication between nerves and muscles is interrupted.
Symptoms
The primary symptom of MG is muscle weakness that worsens with activity and improves with rest. Specific symptoms can include:
Drooping of one or both eyelids (ptosis)
Double vision (diplopia)
Difficulty swallowing (dysphagia)
Slurred speech (dysarthria)
Weakness in the arms, legs, neck, face, fingers, and chest
Fatigue
Difficulty breathing
Causes
MG is caused by an autoimmune reaction, where the body's immune system mistakenly attacks a normal part of itself. In MG, the immune system produces antibodies that block or destroy acetylcholine receptors (AChRs) at the neuromuscular junction. Acetylcholine is a neurotransmitter that transmits signals from nerves to muscles. When AChRs are blocked, muscles cannot receive signals properly, leading to weakness. In some cases, antibodies attack MuSK (muscle-specific kinase), another protein involved in neuromuscular transmission.
Medicine Used
Medications used to manage MG include:
Cholinesterase inhibitors: Such as pyridostigmine (Mestinon), which improve neuromuscular transmission by preventing the breakdown of acetylcholine.
Immunosuppressants: Such as prednisone, azathioprine (Imuran), mycophenolate mofetil (CellCept), cyclosporine, and methotrexate, which suppress the immune system and reduce the production of antibodies.
Monoclonal antibodies: Such as rituximab and eculizumab, which target specific components of the immune system.
Intravenous immunoglobulin (IVIg): Provides a temporary supply of healthy antibodies to modulate the immune system.
Plasma exchange (plasmapheresis): Removes harmful antibodies from the blood.
Is Communicable
Myasthenia Gravis is not communicable. It is not contagious and cannot be spread from person to person.
Precautions
Precautions for individuals with MG include:
Avoiding overexertion and pacing activities to conserve energy.
Getting adequate rest.
Managing stress.
Avoiding extreme temperatures.
Discussing all medications with a doctor, as some drugs can worsen MG symptoms.
Vaccination against influenza and pneumonia is generally recommended.
Wearing an eye patch can help with double vision.
Eating soft foods and taking small bites if having difficulty swallowing.
Keep emergency contact information accessible.
How long does an outbreak last?
MG is a chronic condition, not an acute outbreak. The weakness and other symptoms may fluctuate in severity over time. Periods of increased symptom severity are called "exacerbations" or "flare-ups" and can last for days, weeks, or months. Symptom free remission periods are also possible.
How is it diagnosed?
Diagnosis of MG typically involves:
Medical history and physical examination: Assessing symptoms and muscle strength.
Neurological examination: Testing reflexes, coordination, and cranial nerve function.
Edrophonium (Tensilon) test: Injecting edrophonium, a cholinesterase inhibitor, which temporarily improves muscle strength in MG patients.
Blood tests: To detect antibodies against AChR or MuSK.
Nerve conduction studies and electromyography (EMG): To assess nerve and muscle function.
Single-fiber EMG (SFEMG): A more sensitive test for detecting neuromuscular transmission defects.
CT or MRI scan of the chest: To check for thymoma (tumor of the thymus gland).
Timeline of Symptoms
The onset of MG symptoms can be gradual or sudden. The timeline is highly variable, but it generally follows these patterns:
Early stages: Mild, fluctuating weakness, often affecting the eyes (ptosis, diplopia). Symptoms may come and go.
Progression: Weakness may spread to other muscle groups, such as the face, throat, limbs, and respiratory muscles.
Exacerbations: Periods of worsening symptoms, which can be triggered by illness, stress, medication changes, or other factors.
Remissions: Periods of improvement in symptoms, which can be spontaneous or occur with treatment.
Important Considerations
MG can affect individuals of any age, race, or gender, but it is more common in women younger than 40 and men older than 60.
Myasthenic crisis, a life-threatening condition involving severe muscle weakness and respiratory failure, requires immediate medical attention.
The thymus gland, which plays a role in the immune system, is often abnormal in MG patients. Thymectomy (surgical removal of the thymus gland) may be recommended.
MG can impact pregnancy and childbirth. Women with MG should discuss pregnancy planning with their doctor.
Living with MG requires ongoing medical management, self-care, and support from family, friends, and healthcare professionals.