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Myasthenia Gravis (MG)

Overview

Myasthenia gravis (MG) is a long-term neuromuscular condition that causes skeletal muscle weakening in variable degrees. It is an autoimmune disease in which some antibodies block acetylcholine receptors at a point where nerve and muscle meet. The most typically involved muscles are that of eyes, face, and throat. It can cause double vision, drooping eyelids, difficulty speaking, and difficulty walking.

Epidemiology

Myasthenia gravis is estimated to affect around 20 people per 100,000 people, with women being affected twice as much as males. The overall prevalence is estimated to be between 150 and 200 per million. The incidence in men increases as they get older.

Risk Factors

Certain factors put you at high risk of myasthenia gravis.

  • If you have any family member with an autoimmune condition.
  • If you are suffering from any other autoimmune disease.
  • Though it can affect anyone at any age, it is more common in women under the age of 40 and men over the age of 60.

Causes

Myasthenia gravis is caused by a malfunction in nerve impulse transmission to muscles. It happens when neuron and muscle communication is disrupted at the neuromuscular junction, where nerve cells join the muscles they regulate.

It is an autoimmune condition in which your body’s immune system is not functioning smoothly and producing antibodies that block or kill many of the receptor sites for the neurotransmitter acetylcholine. There are fewer receptor sites available for the nerve signals to be transmitted, causing muscles to fatigue. Sometimes these antibodies block some other proteins named MUSK andP4.

The thymus gland, which is located in the upper chest beneath the breastbone and is part of your immune system, may cause the production of antibodies that cause muscle weakness.

Types

Generalized: eye muscles and muscles of the face, arms, and legs are involved.

Congenital: a rare type of myasthenia gravis when a baby inherits the disease from the mother and suffers lifelong.

Ocular: eye muscles are involved. It can cause droopy eyelids and double vision.

Juvenile: This type of myasthenia gravis is more common in teenage girls.

Transient neonatal myasthenia gravis: Some babies develop mild symptoms after Birth if the mother has myasthenia gravis, but that is usually resolved within a few weeks.

Symptoms

Double vision and sleepy eyes are initial symptoms in most patients. The muscle weakness gets worse during periods of physical activity. However, it gets better following periods of rest. The weakness is usually worse at the end of the day. MG usually begins with ocular (eye) weakness and can advance to a more severe generalized form with weakness in the extremities or muscles that control basic daily activities.

Over weeks or months, weakness progresses from mild to severe, with exacerbations and remissions.

Some other symptoms include:

  • Difficulty in eating.
  • Facial weakness
  • Limb weakness
  • Difficulty in moving neck
  • Difficulty in walking
  • Trouble talking

Sometimes it may involve muscles of your lungs, resulting in difficulty breathing.

Diagnosis

Antibody test: The anti-acetylcholine receptor (AChR) antibody (Ab) test is a must for all patients suspected to have myasthenia gravis, as this test is highly specific. Anti-MUSK antibodies and LRP4 antibodies are the other antibodies that may need to be detected if the results of AChRAb are negative.

Imaging: your doctor will do a chest x-ray to look for the thymus gland, and you might need to undergo a CT scan or MRI for further evaluation.

Nerve Conduction Study: Doctors will repeatedly test the nerve to check if its ability to deliver impulses worsens with exhaustion to identify myasthenia gravis.

Single-Electron Microscopy: It detects electrical activity between nerve and muscle.

Treatment

Although there is no cure for myasthenia gravis, you can live a normal life if you control your symptoms with medication.

Cholinesterase inhibitors: Medications like pyridostigmine (Mestinon, Regional) help nerves and muscles communicate better. These drugs aren't a cure, but they can help some people increase muscle function. The possible adverse effects are nausea, loose motions, perspiration, and excessive salivation.

Corticosteroids: Corticosteroids suppress the immune system, decreasing antibody formation. However, it can have major adverse effects, including bone weakening, weight gain, high sugar levels, and an increased risk of infections.

Immunosuppressant: Other immune-suppressing drugs, such as azathioprine (Azasan, Imuran), mycophenolate mofetil (Cellcept), cyclosporine (Sandimmune, Gengraf, others), methotrexate (Trexall), or tacrolimus, may be prescribed by your doctor. There is an increased risk of liver or renal damage and infections with the use of these medicines.

Plasmapheresis: In severe disease, plasmapheresis is required in which your blood will go thru a filtering machine that will make your blood antibody¬-free.

IVIG: This therapy gives your body normal antibodies to improve your immune system. Benefits normally appear within a week and might continue up to six weeks. Vertigo, shivering, headaches, and fluid retention are some of the most common side effects.
Monoclonal Antibody: These medications are suitable for people who do not respond to other therapies. They can have serious side effects. Eg: rituximab (Rituxan) and eculizumab (Soliris)

Surgical Treatment: Surgery might be needed if you have a tumor in the thymus gland. Thymectomy is always suggested due to the potential of malignancy. Even in those without a tumor, surgical removal of the thymus gland, known as a thymectomy, improves the illness 70% of instances, with myasthenia gravis going to remission in some cases.

Prognosis

Most people with myasthenia can dramatically improve their muscle weakness and enjoy normal or almost normal lives with treatment. Myasthenia gravis can go into remission, either temporarily or permanently, and muscle weakness can subside completely, allowing drugs to be stopped.

Lifestyle Modification

  • Here are some tips to help you cope with myasthenia gravis symptoms:
  • Change your dietary habits.
  • When you have the good muscle power, try to eat.
  • You could discover that eating small meals multiple times a day is more convenient. Also, stick to soft foods and stay away from things that need more chewing, such as raw fruits and vegetables.
  • Install grab bars or railings in situations where you may require assistance, such as close to the bathtub or steps.
  • Move area rugs and keep your floors clean.
  • Keep paths, sidewalks, and drives clean of leaves, snow, and other debris that could cause you to trip outside your home.
  • An eye patch might help if you have double vision.
  • Make use of power tools and appliances. An electric toothbrush may help you better.
  • Join support groups on social media to meet people with similar symptoms.