Myasthenia gravis is a rare autoimmune disease in which one’s own antibodies attack receptors for a substance called acetylcholine (ACh), at a site known as the neuromuscular junction (NMJ), where the nerves meet the muscles they control. This results in occupation by these antibodies of the muscle receptors that receive impulses controlling muscle contraction, leading to reduction in the amount of ACh available at the NMJ, and a consequent decrease in muscular functioning.
While there is no cure at this time, fortunately myasthenia gravis is one of the most treatable autoimmune conditions, owing to a combination of available therapies. These include medications that inhibit the breakdown of ACh at the NMJ (providing more ACh to be used at any available receptors), as well as several other immunomodulating drugs, such as steroids and other immunosuppresives. In addition, a surgery called thymectomy, where the thymus gland remnants (which produce the antibodies) are removed, is another possibility. Use of a procedure known as plasmapheresis, as well as immunoglobulin therapy, may also be utilized, especially in more severe cases.
What are the signs & symptoms of myasthenia gravis?
The signs and symptoms can vary from person to person, but they are all connected to and caused by muscle weakness, which is the predominant and overarching symptom in all patients. While myasthenia gravis can affect any muscles in the body, it most often originally appears to affect either the eye or face and throat muscles, leading to a wide range of symptoms, including drooping of the eyelids, facial muscle pathology, and trouble swallowing. One or both of these scenarios are often the first noticeable signs of the illness, with later progression to muscles of the trunk and limbs, though this is not always the case. Generalized fatigue is also a common complaint from those with the disease.
By far the greatest concern in terms of signs, symptoms and complications is that of myasthenic crisis, where the muscles that control breathing become affected, potentially to the point where artificial ventilation is required. Conversely, a situation known as cholinergic crisis, where there is too much activity at the NMJ can be brought on by excessive therapy for myasthenia gravis. Other major concerns may include difficulty speaking or swallowing, which may lead to pneumonia caused by aspiration of food that is improperly swallowed.
What other autoimmune conditions commonly occur with myasthenia gravis?
Patients with myasthenia gravis do tend to experience other autoimmune disease with more frequency than the general population. Some of these conditions may include diabetes, lupus, rheumatoid arthritis, thyroid disease and MS. In addition, myasthenia gravis sufferers may sometimes develop other neurological conditions, whether autoimmune derived or otherwise.
Since myasthenia gravis affects everyone differently, what does a mild, moderate and severe form of the disease look like? Is it common to progress from mild to severe over time?
The degrees of severity in myasthenia gravis are wholly dependent on which NMJs and muscles are affected, as well as how much muscle fatigue is present in each area. There is no classic presentation that distinguishes mild from moderate from severe. Rather, this classification is based on the level of impairment, areas affected, and weakness and fatigue experienced by the patient. There are also several types of medications that may contribute to exacerbations in this disorder.
In most cases, the patient will progress from his or her initial signs and symptoms to more widespread effects (involving more muscle groups or areas of the body) within weeks to months of initial onset, usually peaking within the first two years. Severity in terms of fatigability may increase as well during this time.
The course of myasthenia gravis tends to somewhat follow a flare and remission pattern, though certain patients may experience near constant disease, while others test positive for associated antibodies, but exhibit few if any symptoms, or symptoms that remain confined to one area rather than spreading. Fortunately, for many patients, a proper treatment regimen allows them to live a relatively healthy and productive life. Research also suggests that early treatment of ocular myasthenia gravis may help prevent progression to more generalized disease.
Questions for your doctor:
- Am I positive or negative for anti-ACh antibodies, and what does this mean clinically?
- Should I have any of the other antibody tests preformed to confirm the diagnosis or direct treatment?
- How can I tell when I need more urgent or emergent treatment for my condition?
- What is the current state of research efforts into causes and therapies for MG?
- Can you recommend a good source of information on all things MG?
- Is it possible that my disorder is something other than MG? If so, what is the differential diagnosis?
- What treatments are appropriate for my case, and how do you/we decide?