Myasthenia Gravis: What It Is, Causes, Symptoms & Treatment

Symptoms of myasthenia gravis may include:

Initial symptoms of myasthenia gravis happen suddenly. Your muscles usually get weaker when you’re active. Muscle strength returns when you rest. The intensity of muscle weakness often changes from day to day. Most people feel strongest at the start of the day and weakest at the end of the day.

In rare instances, myasthenia gravis affects muscles in your respiratory system. You may have shortness of breath or more serious breathing problems. Contact 911 or your local emergency services number if you have trouble breathing. In general, this doesn’t occur suddenly.

Myasthenia gravis (autoimmune type) happens when your body’s immune system mistakenly attacks itself. Researchers aren’t sure why this happens. Studies suggest that certain immune system cells in your thymus gland have trouble identifying what’s a threat to your body (like bacteria or viruses) versus healthy components.

A genetic change causes congenital myasthenia. Antibodies passed from a birthing parent to a fetus during pregnancy cause neonatal myasthenia.

Myasthenia gravis affects communication between nerves and muscles.

When your immune system is working as expected, nerves and muscles work together. It’s similar to a baseball game:

If you have myasthenia gravis, antibodies destroy the receptor sites, blocking nerve-muscle communication. The “catcher” can’t catch the ball, and communication becomes sluggish or doesn’t work at all.

It’s rare to inherit autoimmune myasthenia gravis. You can inherit congenital myasthenia or neonatal myasthenia. Types where inheritance happens usually occur in an autosomal recessive pattern where you need two genes, one from each biological parent, to experience symptoms.

Myasthenia gravis is most common among women and people assigned female at birth around age 40 and men and people assigned male at birth after age 60. The condition can affect anyone at any age.

You may be more at risk of developing myasthenia gravis if you:

If you have myasthenia gravis, your symptoms could trigger (start) if you:

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Weakness and fatigue from myasthenia gravis can keep you from participating in activities you enjoy. This may lead to stress and depression. However, studies also show that most people with myasthenia gravis can tolerate light activities and exercises on a routine basis.

Up to 1 in 5 people with myasthenia gravis experience a myasthenic crisis or severe respiratory muscle weakness. You may need a respirator or other treatments to help you breathe. This is a life-threatening medical emergency. An estimated 20% of people with myasthenia gravis experience at least one myasthenic crisis in their lifetime.

Many people with myasthenia gravis have thymus gland conditions that may trigger symptoms. The thymus is a small organ in your upper chest. It’s part of your lymphatic system. It makes white blood cells that fight infections. Two-thirds of people with myasthenia gravis have overactive thymic cells (thymic hyperplasia). About 1 in 10 people with myasthenia gravis have thymus gland tumors called thymomas, which may be benign (not cancer) or cancerous.