INTRODUCTION
Myasthenia gravis is a rare, potentially fatal chronic autoimmune disorder in which circulating autoantibodies directed against components of the neuromuscular junction (NMJ) of skeletal muscles – most commonly the nicotinic acetylcholine receptor (ACHR) and associated proteins in the postsynaptic membrane – block neuromuscular transmission, resulting in muscle weakness. The term “myasthenia gravis” is derived from the Greek words “my” (muscle), “asthenia” (weakness), and “gravis” (severe). Muscle weakness typically worsens with continued activity, improves with rest, and ranges in severity from mild ocular muscle weakness to severe generalized weakness involving the respiratory muscles, which can lead to impending respiratory failure.
The Etiology of Myasthenia gravis The occurrence of myasthenia gravis (autoimmune type) is attributed to the misguided attack of the body’s immune system on itself. The exact reason behind this phenomenon remains uncertain to researchers. However, studies indicate that specific immune system cells within the thymus gland struggle to distinguish between harmful elements such as bacteria or viruses and the body’s healthy components. Congenital myasthenia is the result of a genetic mutation, while neonatal myasthenia is caused by antibodies transmitted from a mother to her unborn child during pregnancy.
The risk factors for myasthenia gravis
vary depending on age and gender. It is more commonly found in women and individuals assigned female at birth around the age of 40, as well as men and individuals assigned male at birth after the age of 60.
1. However, this condition can affect anyone regardless of age or gender. It is more commonly found in women and individuals assigned female at birth around the age of 40, as well as men and individuals assigned male at birth after the age of 60. However, this condition can affect anyone regardless of age or gender.
2. certain factors may increase your risk of developing myasthenia gravis. These include having a history of other autoimmune conditions such as rheumatoid arthritis and lupus, as well as having thyroid disease.
3. If you already have myasthenia gravis, certain triggers could worsen your symptoms. These triggers include taking medications for malaria and heart arrhythmias, undergoing surgery, or experiencing an infection.
4. Additionally, stress, fatigue, and pregnancy can also exacerbate symptoms in individuals with myasthenia gravis.
WHAT ARE THE COMPLICATIONS OF MG?
· The complexity of myasthenia gravis can lead to a myasthenic crisis, often triggered by infections, stress, or acute illnesses.
· Complications from treatment may arise, such as long-term steroid side effects including osteoporosis, hyperglycemia, cataracts, weight gain, hypertension, and avascular necrosis of the hip. Additionally, there is a potential risk of lymphoproliferative malignancies and opportunistic infections like systemic fungal infections, tuberculosis, and Pneumocystis carinii pneumonia with prolonged immunosuppressive therapy.
· Cholinergic crisis can occur as a result of excessive ACH at nicotinic and muscarinic receptors due to the use of cholinesterase inhibitors.
PATHOPHYSIOLOGY
In the human body, nerves communicate with muscles by releasing neurotransmitters (ACH) that communicate with muscle cells at the neuromuscular junction. In MG, the immune system produces antibodies that block /destroy the binding of acetylcholine Fewer nerve signals cause muscle weakness.
SIGNS AND SYMPTOMS
W -Weakness ( face /neck/arms/legs)
E- eyelid drooping (ptosis)
A-appearance (zero expressions)
K- keeps choking/ gagging
N-no energy
E- extraocular movements (double blurred vision)
S-slurred speech
S- shortness of breath
HALLMARK SIGN: weakness gets worse with activity but improves after resting the muscles.
What is the relationship between myasthenia gravis and the thymus gland?
The relationship between myasthenia gravis and the thymus gland lies in the fact that many individuals with myasthenia gravis experience thymus gland conditions that can potentially exacerbate symptoms. The thymus gland, located in the upper chest, is a vital component of the lymphatic system responsible for producing white blood cells that combat infections. Approximately two-thirds of individuals with myasthenia gravis exhibit hyperactive thymic cells, a condition known as thymic hyperplasia. Additionally, around 1 in 10 individuals with myasthenia gravis develop thymus gland tumors known as thymomas, which can either be benign or cancerous.
What are the methods used to diagnose myasthenia gravis?
To diagnose myasthenia gravis, a thorough physical examination will be conducted by your healthcare provider, along with a series of detailed questions to gather information about your symptoms and medical background. The diagnosis is confirmed through testing, which may involve various procedures.
- Blood anti-body tests, Around 85% of individuals diagnosed with myasthenia gravis exhibit abnormally elevated levels of acetylcholine receptor antibodies in their bloodstream. A smaller percentage, approximately 6%, have muscle-specific kinase (MuSK) antibodies.
- imaging scans like MRI or CT scans to assess the thymus gland, and Electromyography (EMG) to evaluate the electrical activity of muscles and nerves, identifying any issues with nerve-muscle communication.
What are the treatment options for myasthenia gravis?
Myasthenia gravis does not have a cure. Treatment options for myasthenia gravis include medications to reduce symptoms, monoclonal antibodies to suppress an overactive immune system, plasma exchange to remove harmful antibodies, IV or SQ immunoglobulin infusions, and surgery such as thymectomy to remove the thymus gland.
In addition to the mentioned treatment options, several other approaches can be considered for managing myasthenia gravis. These include:
PHARMACOLOGICAL TREATMENT:
1. Cholinesterase inhibitors: Medications such as pyridostigmine can be prescribed to improve muscle strength and reduce weakness by inhibiting the breakdown of acetylcholine, a neurotransmitter involved in muscle contraction.
2. Corticosteroids: Drugs like prednisone may be used to suppress the immune system and reduce inflammation, thereby improving muscle function. However, long-term use of corticosteroids can have significant side effects.
3. Immunosuppressants: Medications such as azathioprine, mycophenolate mofetil, or cyclosporine can be prescribed to suppress the immune system and reduce the production of harmful antibodies.
4. Rituximab: This monoclonal antibody targets and depletes B cells, which are responsible for producing the antibodies that attack the neuromuscular junction in myasthenia gravis.
5. Thymus-targeted therapy: In cases where the thymus gland is overactive or abnormal, treatments such as thymectomy (surgical removal of the thymus gland) or thymus irradiation may be considered. This can help improve symptoms and reduce the production of autoantibodies.
6. Intravenous or subcutaneous immunoglobulin infusions: High-dose infusions of immunoglobulins, which are antibodies derived from donated blood, can help temporarily modulate the immune response and improve muscle strength.
7. Plasmapheresis: This procedure involves removing the patient’s blood plasma, which contains the harmful antibodies, and replacing it with donor plasma or a plasma substitute. Plasmapheresis can provide short-term relief from symptoms by reducing circulating autoantibodies.
NON PHARMACOLOGICAL TREATMENT
While the exact causes of MG remain unknown and unchangeable, certain lifestyle adjustments can help manage flare-ups.
These lifestyle modifications include:
1. Ensuring an adequate amount of sleep.
2. Taking regular rest periods as needed.
3. Avoid strenuous or exhausting activities.
4. Steer clear of extreme temperatures, both hot and cold.
5. Effectively managing emotional stressors.
6. Taking necessary precautions to avoid infections.
7. Collaborating with your healthcare provider to avoid medications that may exacerbate symptoms.
Here are some strategies to alleviate The symptoms of myasthenia gravis:
1. Engage in regular exercise to enhance muscle strength, improve your mood, and increase your energy levels. However, it is important to consult with your healthcare provider before initiating any exercise program to ensure its safety.
2. Ensure that your meals contain an ample amount of protein and carbohydrates to provide you with additional energy.
3. Prioritize and tackle your most demanding tasks earlier in the day when you feel your best.
Physical therapy: Working with a physical therapist can help improve muscle strength, coordination, and mobility. They can provide exercises and techniques to manage fatigue and optimize daily functioning.
What is the prognosis for myasthenia gravis?
Myasthenia gravis is a manageable condition with symptoms that can vary in severity. Typically, symptoms peak in severity within one to three years of diagnosis.
With proper treatment, individuals with myasthenia gravis can lead full and active lives. In some cases, the condition may go into remission, where symptoms temporarily or permanently stop. If remission occurs, your healthcare provider may make adjustments to the treatment plan.
In terms of life expectancy, most individuals with myasthenia gravis have a normal life expectancy. However, life-threatening situations can arise during a myasthenic crisis, impacting the ability to breathe.
