Common Complications of Myasthenia Gravis

Reviewed by: HU Medical Review Board | Last reviewed: May 2021

Myasthenia gravis (MG) is a chronic autoimmune disease that attacks what are called voluntary muscles. Voluntary muscles are those that we can choose to control. This includes muscles that control the eyes, mouth, neck, arms, legs, and sometimes, breathing.

With MG, these muscles become weak and tire easily, especially when used. The muscle weakness is often better in the morning and gets worse later in the day. MG comes with several common complications, such as:1-9

  • Depression, anxiety, and panic disorders
  • Heart disease
  • Issues related to long-term steroid use
  • Thymoma (cancer of the thymus gland)
  • Myasthenic crisis
  • Other autoimmune diseases

Mental health issues

The unpredictable nature of MG can create great stress for people with the condition. This stress in turn makes them more likely to develop depression, anxiety, and panic disorders.

Several studies have found that depression and anxiety become more likely as MG symptoms get worse and the longer someone has MG. This is especially true if muscle weakness limits daily activities or impacts the ability to work.1,2

It is important to treat mental health issues because stress and untreated depression can make MG symptoms worse.

Heart disease and diabetes

Cardiovascular disease (diseases of the heart and blood vessels) is common in people with myasthenia gravis. One study followed 127 people with MG for 10 years. It found that after age 50 nearly all had developed:3

  • High blood pressure
  • Heart disease
  • Diabetes

People with MG are no more likely than the general population to have heart disease or die from heart disease. However, people with MG are at risk of muscle weakness spreading to their heart muscle. Men with late-onset MG are more at risk of developing diabetes, though it is not clear if this is due to the MG or to long-term steroid use.3

Long-term steroid use

Steroids are a group of drugs known as immunosuppressants. This means that steroids suppress (reduce or stop) the body from attacking healthy tissue. This helps relieve the symptoms of MG. However, using steroids over years can create other problems, including:4

  • Osteoporosis (weak bones)
  • Cataracts
  • High blood sugar
  • Weight gain
  • Problems with hip bones
  • High blood pressure
  • Getting infections more easily
  • Stomach irritation and ulcers


The thymus gland sits in the chest just behind the breast bone. This gland plays a key role in how the immune system works. In people with MG, the thymus gland is often overactive, too large, or has tumors. Tumors on the thymus gland are called thymomas. These tumors may be cancerous or non-cancerous.

One of every 10 people with MG will have a thymoma. People whose MG began between ages 30 and 60 have higher rates of thymoma. People with a thymoma have more severe MG.5

A thymectomy is a surgery to remove any tumors and sometimes the whole thymus gland. Studies show that a thymectomy that removes the whole gland helps relieve symptoms, sometimes greatly, so that fewer immunosuppressants are needed.5

Myasthenic crisis

There are myasthenic flares and myasthenic crises. A flare is different from person to person. It generally happens when some or all of the muscles involved in MG get weaker. This may cause new or worsening:6

  • Double vision
  • Weakness
  • Falls
  • Unsteadiness walking
  • Problems swallowing

A myasthenic crisis results in weakness of the breathing (respiratory) muscles. It is a potentially life-threatening situation that requires immediate emergency care. A myasthenic crisis often develops after days or weeks of slowly worsening symptoms but can also come on suddenly.6

Myasthenic crisis is not a common symptom, but it does happen to about 1 in 5 people with MG at least once.6,7

Other autoimmune diseases

Myasthenia gravis is an autoimmune condition. Between 1 in 10 and 2 in 10 people with MG have another autoimmune condition. Other autoimmune disorders common in people with MG include:8,9

  • Thyroiditis
  • Lupus
  • Multiple sclerosis
  • Rheumatoid arthritis
  • Sjogren’s syndrome
  • Scleroderma
  • Ulcerative colitis

Having a second autoimmune condition is more common in people with early-onset MG or who have an enlarged thymus gland.8,9

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