An autoimmune, neuromuscular condition that weakens skeletal muscles that regulate physical movement as well as breathing and swallowing, myasthenia gravis (MG) is a very complex disease to diagnose and treat. While a cure is not yet out there, symptomatic support helps disease management and allows a good quality of life. Most patients diagnosed with MG have a normal life expectancy.
Typical disease symptoms include:
- weakness of the eye muscles (called ocular myasthenia)
- drooping of one or both eyelids (ptosis)
- blurred or double vision (diplopia)
- a change in facial expression
- difficulty swallowing
- shortness of breath
- impaired speech (dysarthria)
- weakness in the arms, hands, fingers, legs, and neck
- respiratory failure is a very serious symptom that requires immediate medical attention
While MG affects all racial/ethnic groups and is observed among both men and women, it may be more common among women under 40 years and men over 60 years.
What Causes Myasthenia Gravis?
MG stems from the body’s failure to transmit nerve impulses to muscles because of a person’s autoimmune condition. The person’s own antibodies may change or destroy proteins (muscle-specific serum kinase or MuSK and lipoprotein-related protein 4 or LRP-4) that help transmit electrical signals from the nerves to muscles. This can compromise proper functioning of various muscles in the body.
What are autoimmune diseases? Your immune system protects you from disease and infection by attacking germs that get into your body, such as viruses and bacteria. Your immune system can tell that the germs aren't part of you, so it destroys them. If you have an autoimmune disease, your immune system attacks the healthy cells of your organs and tissues by mistake. There are more than 80 types of autoimmune diseases. They can affect almost any part of your body. For example, alopecia areata is an autoimmune disease of the skin that causes hair loss. Autoimmune hepatitis affects the liver. In type 1 diabetes, the immune system attacks the pancreas. And in rheumatoid arthritis, the immune system can attack many parts of the body, including the joints, lungs, and eyes. - https://medlineplus.gov/autoimmunediseases.html
Problems with the thymus gland could also cause MG. Typically, the thymus gland grows during childhood and through puberty but starts shrinking after. When this process fails and the gland stays large, it results in clusters of immune cells in the thymus gland and even tumor development. The gland may provide incorrect instructions to new immune cells, resulting in them attacking the proteins that promote transmission of nerve signals.
Diagnosis Can Be Challenging
Vague and some common symptoms of this condition—such as weakness—can delay diagnosis of MG, often up to several months. Additionally, if a person has any other autoimmune condition, it can further complicate and delay diagnosis. A confirmed diagnosis will require some specific tests:
- Neurological exam: to test reflexes, muscle strength, muscle tone, sense of touch and sight, posture, gait etc.
- Blood test: to check the presence of antibodies to the acetylcholine receptor (AChR) and MuSK
- Ice test: can accentuate muscle weakness in MG patients and is an easy-to-perform diagnostic test.
- Nerve conduction studies/repetitive nerve stimulation: a small electrical impulse to a nerve results in muscle contraction. However, in patients with MG, their nerves fatigue easily and don’t bounce back quickly.
- Single fiber electromyography (EMG): a sterile needle electrode is inserted into a muscle, which the patient gently contracts or activates. Computer analysis of several recorded electrical signals in that muscle may show abnormal neuromuscular transmission, which is typical of MG as well as some other neuromuscular disorders.
- Imaging: Computed tomography (CT) or magnetic resonance imaging (MRI) is often done to identify an abnormal thymus gland or a thymus gland tumor (thymoma).
Primary treatment options are:
- Symptomatic treatment with acetylcholinesterase inhibitor
- Chronic immunotherapies, including glucocorticoids, nonsteroidal immunosuppressive drugs, and nonsteroidal immunomodulatory agents
- Rapid-acting immunomodulating treatments such as therapeutic plasma exchange (plasmapheresis) and intravenous immunoglobulin (IVIg) for rescue or maintenance therapy
- Surgery to remove the thymus (thymectomy): this can be minimally invasive, using an endoscope or a robotic system
For those seeking clinical trials for MG, here’s some information: https://myasthenia.org/Research/Apply-to-Clinical-Trials.
When developing your treatment plan, the treating physician will consider several factors: age, gender, other illnesses, as well as the type of MG (ocular or generalized) and the presence of MG antibodies.
For patients who are seronegative—meaning those who test negative for the marker antibodies (AChR, MuSK, and/or LRP-4)—treatment options are limited. These patients are most likely to have ocular MG. Diagnosis is often tricky in this patient population and treatment options are limited.
Myasthenia Gravis Support is Alive and Well – by Drea Carbone
Surabhi Dangi-Garimella, Ph.D. is a biologist with academic research experience, who brings her skills and knowledge to the health care communications world. She provides writing and strategic support to non-profit groups via her consultancy, SDG AdvoHealth, LLC.