A myasthenic crisis is a serious complication of myasthenia gravis. It causes respiratory failure, which is a life-threatening condition.

Myasthenia gravis is an autoimmune condition that causes weakness in voluntary muscles. These are muscles that attach to your bones and control movement in your body, including muscles that help you breathe.

The National Institute of Neurological Disorders and Stroke reports that an estimated 15–20% of people with myasthenia gravis will have at least one myasthenic crisis.

Read on to learn more about this complication, including how to prevent, recognize, and manage it.

A myasthenic crisis is a life-threatening complication of myasthenia gravis. It happens when muscles that control breathing weaken to the point that you need medical support to recover.

Older adults with myasthenia gravis are more likely than younger adults to have a myasthenic crisis.

Your risk of a myasthenic crisis may be increased if you:

  • have myasthenia gravis that is severe or untreated
  • have had a myasthenic crisis in the past
  • have weakness that affects your throat (oropharynx)
  • test positive for muscle-specific kinase (MuSK) antibodies
  • have a thymoma, a type of tumor that can develop in your chest

Some people don’t know they have myasthenia gravis until they have a myasthenic crisis.

A myasthenic crisis usually develops over several hours, days, or weeks. But it sometimes develops more quickly.

Potential signs and symptoms of a myasthenic crisis include:

  • difficulty breathing
  • shallow breathing
  • weak cough
  • general weakness
  • weakness in your limbs
  • increased bulbar weakness, which may cause:
    • drooling
    • lip trembling
    • loss of gag reflex
    • tongue or jaw weakness
    • difficulty swallowing or talking
    • nasal or hoarse voice

Seek medical help right away if you think you may be developing or experiencing a myasthenic crisis. Early treatment is important to improve your outcome.

Your nervous system uses a chemical known as acetylcholine to send signals to voluntary muscles. If you have myasthenia gravis, your immune system blocks, changes, or destroys proteins that help acetylcholine travel between nerves and muscle fibers. This is what stops the muscle from contracting properly and causes muscle weakness.

Myasthenia gravis can affect the muscles in your throat, chest, and diaphragm that help control your airway and breathing. Weakness in these muscles can make it difficult to breathe and lead to a myasthenic crisis.

Certain triggers may lead to a myasthenic crisis, including respiratory infections.

Other potential triggers include:

  • an adverse reaction to medication
  • surgery
  • injury
  • pregnancy
  • childbirth
  • stress

About 30–40% of myasthenic crises have an unknown trigger.

Following your treatment plan for myasthenia gravis can help reduce your risk of a myasthenic crisis. Your doctor may prescribe medication and other treatments to manage myasthenia gravis.

Taking steps to avoid or manage potential triggers may also reduce your risk of a myasthenic crisis. For example:

  • Lower your risk of respiratory infections by getting recommended vaccinations, avoiding close contact with people who are sick, and cleaning your hands regularly with soap and water or alcohol hand gel.
  • Ask your doctor how you can manage the risk of a myasthenic crisis before you change medications, undergo a scheduled surgery, get pregnant or give birth.
  • Take steps to limit preventable injuries and stress.

Getting early treatment for symptoms of a myasthenic crisis may help limit its severity and promote your recovery.

Your doctor will diagnose a myasthenic crisis by:

  • considering your symptoms
  • conducting a physical exam
  • ordering tests to evaluate your respiratory function

He or she will also order tests to rule out other potential causes of your symptoms, such as a blood clot in your lungs, heart failure, or acute respiratory distress syndrome (ARDS).

Most people who have a myasthenic crisis already know they have myasthenia gravis. However, some people develop a myasthenic crisis without already having a diagnosis of myasthenia gravis.

Your doctor can diagnose myasthenia gravis by ordering blood tests and electrical tests of your nerves and muscles. They may order other tests as well to check for signs of myasthenia gravis or rule out other diagnoses.

You’ll likely receive treatment for a myasthenic crisis in the intensive care unit (ICU) of a hospital.

Your treatment may include any of the following:

  • insertion of a tube into your windpipe, known as intubation
  • breathing support from a machine known as a ventilator
  • breathing exercises to help improve lung function
  • airway suctioning to remove mucus and other secretions from your airways
  • medication to open your airways, alter your immune system, or manage symptoms
  • plasma exchange or intravenous immunoglobulin, which temporarily alters your immune system by replacing harmful immune proteins with healthy donor proteins
  • fluids and dietary supplements to keep you hydrated and your nutritional needs met

Your care team will also monitor you for signs of complications, which may require other treatments. They can help you and your loved ones learn about your outlook and treatment options.

Your doctor may prescribe rehabilitation therapy or other treatments to support your recovery after you leave the hospital. They may refer you to a respiratory therapist or other rehabilitation specialists. You may also benefit from psychological counseling to manage the emotional stress that a myasthenic crisis can cause.

A myasthenic crisis is a complication of myasthenia gravis that causes serious breathing difficulties.

It may be triggered by a respiratory infection, adverse reaction to medication, or other physical or emotional stress. The trigger is not always known.

Following your treatment plan for myasthenia gravis can help reduce your risk of a myasthenic crisis. Your doctor may prescribe medication and other treatments for myasthenia gravis. They may also share tips for managing potential triggers of a myasthenic crisis.

It’s important to seek medical care right away if you develop breathing difficulties or other symptoms of a myasthenic crisis. You may need to receive treatment in a hospital to support your recovery.