Myasthenia Gravis

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Overview

Myasthenia gravis (MG) is the most common disorder affecting the neuromuscular junction (NMJ) of the skeletal muscles. The classic presentation is a fluctuating weakness that is more prominent in the afternoon. It usually involves muscles of the eyes, throat, and extremities. The reduced transmission of electrical impulses across the neuromuscular junction due to the formation of autoantibodies against the specific postsynaptic membrane proteins consequently causes muscle weakness. A wide variety of conditions can precipitate MG, such as infections, immunization, surgeries, and drugs. 

Myasthenia gravis causes a significant number of complications. These include myasthenic crisis, an acute respiratory paralysis that requires intensive care, as well as adverse events due to long term medication treatment like opportunistic infections and lymphoproliferative malignancies.

A complete understanding of the pathophysiologic mechanisms, clinical manifestations, treatment strategies, and complications of myasthenia gravis is necessary for better patient care and outcomes.

Symptoms

weakness of the eye muscles (called ocular myasthenia)

drooping of one or both eyelids (ptosis)

blurred or double vision (diplopia)

a change in facial expression.

difficulty swallowing.

shortness of breath.

impaired speech (dysarthria)

Causes

MG is an autoimmune disease. For unknown reasons, the body’s immune system attacks itself.

In someone with a healthy immune system, nerves and muscles communicate a bit like a tiny baseball game:

Nerves (the pitcher) send signals to muscles (the catcher) across a synapse (connection) called the neuromuscular junction. To communicate, nerves release a molecule called acetylcholine (the baseball).

Muscles have sites called acetylcholine receptors (the catcher’s glove). The acetylcholine binds to the receptors in the muscle tissue, like a ball landing in a glove.

When the acetylcholine binds to the receptor, it triggers the muscle fiber to contract.

In a healthy person, nerves signal muscles work effortlessly, like one ballplayer catching a ball and throwing it to a teammate.

Risk factors

Risk factors for myasthenia gravis include having a personal or family history of autoimmune diseases. Men over 60 and women under 40 are at higher risk. What are the symptoms? The most common symptoms are drooping eyes, double vision, difficulty chewing, choking on food, and muscle weakness.

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Complications

Left untreated, MG may lead to complications. Talk with your doctor about your personal risk.

Myasthenic crisis

One of the most dangerous potential complications of MG is a myasthenic crisis. It’s estimated that 15 to 20 percentTrusted Source of people with MG will experience at least one episode of this life threatening complication.

During a myasthenic crisis, you may experience severe muscle weakness that leads to respiratory failure, according to the NINDSTrusted Source.

Talk with your doctor about your risks. If you start to have trouble breathing or swallowing, call 911 or go to your local emergency room immediately.

Prevention

Try to prevent infections with careful hygiene and by avoiding sick people.

Treat infections promptly.

Do not become overheated or too cold.

Avoid overexertion.

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