The thymus is a small organ, but for some patients with myasthenia gravis (MG) it can play a big role in the disease. What is the thymus gland, and how can it impact treatment?
What is the thymus gland?
The thymus gland is part of the body’s immune system. It is located in the chest between the lungs, behind the breastbone.
The main role of the thymus is to train specialized white blood cells called T cells. White blood cells are produced in the bone marrow and then travel to the thymus, where they mature into T cells. In the thymus, T cells learn how to tell the body’s healthy cells apart from ones that may cause harm, such as germs, viruses and cancer cells.
Generally, the thymus gland is most active in childhood. In most people, it shrinks after puberty and plays less of a role in adulthood. But that’s not the case for many with MG.
Why is the thymus a problem in MG?
Many people with MG have problems with their thymus.
Around 65% to 70% of people with AChR antibody-positive MG have thymic hyperplasia, or inflammation of the thymus gland.
About 15% to 20% of patients with MG have thymomas, tumors of the thymus gland. Thymomas aren’t usually cancerous, and these tumors rarely spread beyond the thymus.
Though researchers know there is a connection between the thymus and MG, the exact reasons why many people with MG have thymus problems isn’t well understood. Thymus problems are common enough that it’s often recommended newly diagnosed patients receive a CT scan or MRI imaging to check for any thymic abnormalities. Changes to the thymus can have implications for the symptom burden of MG and its treatment options.
What is a thymectomy?
The removal of the thymus gland, or thymectomy, has been shown to lead to remission for many people with MG; even if remission doesn’t happen, a thymectomy can help reduce symptoms, improve muscle strength and lead to less dependence on immunosuppressive drugs.
Thymectomies are often recommended for patients under 60 years old with moderate to severe muscle weakness, and for patients with thymoma or thymic hyperplasia. Thymectomies are often performed using minimally invasive techniques and small incisions, which can mean easier healing after surgery. Each patient must be evaluated to be sure they are physically strong enough to manage the operation and recovery, and are not at risk of the surgery causing a myasthenia crisis.
Read more about myasthenia gravis treatment and care
How else is the thymus a problem?
For patients with a thymoma, a thymectomy is often recommended for reasons beyond just MG treatment. As a thymoma grows, it presses on the lungs, heart and major blood vessels. This can lead to the following symptoms:
- Shortness of breath.
- Hoarse voice.
- Chest pain.
- Persistent cough.
- Swelling in the face, neck or upper chest.
In some cases, a thymoma can also trigger other autoimmune disorders, such as thyroid problems, low red blood cells or low white blood cells.
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