Myasthenia Gravis - Symptoms and Causes

What is Myasthenia Gravis?

Myasthenia gravis is a condition that causes muscle weakness and rapid fatigue. It happens when signals between nerves and muscles don’t work properly.

People with this disorder find that muscles they can normally control become weak and tire quickly.

The disease can affect anyone at any age. Women under 40 and men over 60 have higher rates of diagnosis.

While there is no cure for myasthenia gravis, treatments can help manage symptoms.

Signs and Symptoms

Problems with Eye Muscles

More than half of people with myasthenia gravis first notice problems with their eyes. These symptoms include:

Droopy eyelids (one or both eyes)
Double vision may appear horizontally or vertically
Vision problems that improve when closing one eye

The muscle weakness gets worse with use and improves with rest. This pattern of symptoms coming and going is typical, though they tend to worsen over time.

Face and Throat Issues

About 15% of people first experience symptoms in their face and throat muscles. These can affect daily activities in several ways:

Speech changes: Words may sound soft or nasal.
Swallowing difficulties: You might choke easily on food or drinks.
Eating problems: Chewing muscles may tire during meals, especially with tough foods.
Facial expression changes: Smiles might look unnatural or snarl-like.

Neck and Limb Weakness

Weakness can also affect other body parts:

Neck muscles may become too weak to hold up the head
Arm weakness makes daily tasks harder
Leg weakness can change how you walk
Symptoms typically worsen with activity and improve with rest

When to Seek Medical Help

Contact your doctor if you experience:

Breathing problems
Vision changes
Trouble swallowing
Difficulty chewing food
Problems walking
Weakness in arms or hands
Inability to hold your head up properly

These symptoms might start mild but often get worse over the first few years after the condition begins.

Since muscle weakness comes and goes, keep track of when symptoms appear and what makes them better or worse to help your doctor understand your condition.

Why Myasthenia Gravis Happens

Immune System Attacks

Your muscles and nerves work together through chemicals called neurotransmitters. These chemicals fit into special receptor sites on muscle cells.

In myasthenia gravis, your immune system makes antibodies that block or destroy these receptor sites for acetylcholine, an important neurotransmitter.

With fewer working receptor sites, your muscles get fewer signals from nerves, causing weakness.

Your body might also make antibodies against proteins called MuSK and LRP4. These proteins help form connections between nerves and muscles. When antibodies attack these proteins, it can also cause myasthenia gravis.

Some people have what doctors call “seronegative” myasthenia gravis. This means tests don’t find the known antibodies, but the condition is still likely caused by immune system problems that haven’t been identified yet.

Thymus Problems

The thymus is a small gland in your upper chest that helps your immune system. Many researchers believe the thymus makes or helps produce the antibodies that cause myasthenia gravis.

While the thymus normally gets smaller as you age, people with myasthenia gravis often have an unusually large thymus. Some also develop thymus tumors called thymomas. These tumors are usually not cancerous, though they can be in some cases.

Additional Triggers

Several other factors can cause or worsen myasthenia gravis:

Inherited forms: Rarely, babies are born with myasthenia gravis from mothers who have the condition (neonatal myasthenia gravis).
- With prompt treatment, these babies usually recover within two months. Some children are born with a rare genetic form called congenital myasthenic syndrome.
Factors that can worsen symptoms:
- Being tired
- Getting sick or having an infection
- Having surgery
- Feeling stressed
- Taking certain medications (beta blockers, some antibiotics, certain anesthetics)
- Pregnancy
- Menstrual periods

These triggers don’t cause the disease but can make symptoms worse in people who already have it.

Possible Complications

When Breathing Becomes Difficult

Breathing problems can become dangerous for people with myasthenia gravis. This happens when the muscles needed for breathing get too weak to work properly.

When this occurs, the person needs emergency help right away. Doctors may use machines to help with breathing until the person recovers.

Treatment often includes medicines and special procedures that clean the blood to help the person breathe on their own again.

Growths in the Thymus

Some people with myasthenia gravis develop growths in their thymus gland. This gland sits under the breastbone and helps the immune system work.

These growths, called thymomas, are usually not cancerous. However, they still need medical attention and may require surgery to remove them.

Myasthenia Gravis – Symptoms and Causes