Myasthenia gravis (MG)

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What is myasthenia gravis?

Myasthenia gravis (MG) is a rare autoimmune condition that causes muscle weakness. It happens when the immune system interferes with signals between nerves and muscles. MG only affects the muscles you can voluntarily control, like the ones in your arms, legs, or eyelids. It also commonly affects the muscles used for breathing, swallowing, and eye movements.

MG is also closely linked to conditions of the thymus gland, a small organ in the chest that plays a role in the immune system. Some people with MG have changes in the thymus, including thymic hyperplasia or a thymic tumor called a thymoma.

At Penn Medicine, a coordinated team works together to diagnose and treat these conditions. Our Myasthenia Gravis and Thymoma Program is one of the few in the nation that coordinates all your care in one place, giving you access to experts in every field from neurology to thoracic surgery.

How these conditions may affect you

While muscle weakness is the main sign of MG, the condition is often linked to changes in your thymus gland.

Tests used to confirm a diagnosis

Diagnosis begins with a careful review of symptoms and a physical exam. Specialized blood testing helps confirm MG and evaluate the thymus gland. Imaging tests are used to look for thymic abnormalities. In most cases, imaging provides enough information, and a biopsy isn’t needed unless the mass is large or unclear.

Electromyography
Electromyography (EMG) is a test that checks the health of the muscles and the nerves that control the muscles.
Single-fiber electromyography (SFEMG)
This test is a specialized diagnostic technique used to assess the function of individual muscle fibers.
CT scan
A CT scan helps diagnose traumatic injuries, cancer, vascular diseases, and many other conditions.
MRI
An MRI provides high-resolution images of the brain, spine, and many other structures in the body.

Treating myasthenia gravis and thymoma

To improve the muscle weakness caused by myasthenia gravis, your care team will recommend medicines to suppress the immune system. In addition to pills, there are emergency treatments available for people who are short of breath or are having trouble swallowing. These include intravenous gamma globulin (IVIG) and plasma pheresis.

Thymic hyperplasia by itself doesn't require any treatment, but associated conditions like hyperthyroidism may. In people with MG and thymic hyperplasia, your provider may recommend surgery to remove the thymus gland.

Thymoma is most often treated with surgery to remove the tumor. Additional therapies may be recommended if the tumor has spread beyond the thymus.

Chemotherapy
This treatment uses strong medicines to target and eliminate cancer cells and to prevent their spread.
Proton therapy
This noninvasive, precise radiation therapy uses high-energy protons to damage the DNA in cancer cells.
Radiation therapy
External radiation and internal radiation therapies are used to treat cancer and benign tumors.

Advanced radiation therapy

When radiation therapy is part of treatment, Penn Medicine offers highly precise options. Proton therapy, available at select Penn Medicine locations in Pennsylvania and New Jersey, targets tumors while limiting radiation exposure to nearby organs like the heart and lungs.

The center uses advanced pencil beam scanning technology, which allows radiation to be delivered with exceptional accuracy. This approach may reduce side effects during treatment and long after therapy is complete. We also have clinical trials for people who aren’t responding to conventional treatments.

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