A Guide for Patients and Families What is... Myasthenia Gravis Myasthenia gravis (MG) is a chronic autoimmune MG is not inherited, and it is not contagious. Although disease — a disease that occurs when the immune MG is not hereditary, genetic susceptibility appears to system mistakenly attacks the body’s own tissues. play a role in it. Occasionally, the disease may occur in more than one member of the same family. In MG, the immune system attacks and interrupts the connection between nerve and muscle, called the MG causes weakness in muscles that control the neuromuscular junction (NMJ). This causes weakness eyes, face, neck, and limbs. Symptoms include partial in the skeletal muscles, which are responsible for paralysis of eye movements, double vision, and droopy breathing and moving parts of the body. eyelids, as well as weakness and fatigue in neck and jaws with problems in chewing, swallowing, and holding In most cases of MG, the immune system targets the up the head. acetylcholine receptor — a protein on muscle cells that is required for muscle contraction. Muscle weakness in MG gets worse with exertion and improves with rest. About 85 percent of people with MG have antibodies against the acetylcholine receptor in their blood. The Approximately 10-20 percent of people with antibodies target and destroy many of the acetylcholine MG experience at least one myasthenic crisis, an receptors on muscle. Consequently, the muscle’s emergency in which the muscles that control breathing response to repeated nerve signals declines with time, weaken to the point where the individual requires a and the muscles become weak and tired. ventilator to help them breathe. This condition may be triggered by infection, stress, surgery, or an adverse About 15 percent of individuals with MG are seronegative reaction to medication, and usually requires immediate for antibodies to the acetylcholine receptor, meaning the medical attention. antibodies aren’t detectable in their blood (serum). It’s been discovered that a large fraction of these individuals There is no known cure for MG, but there are treatments have antibodies to muscle-specific kinase (MuSK), that can control symptoms and allow people with MG to a protein that helps organize acetylcholine receptors have a relatively high quality of life. Most individuals on the muscle cell surface. with the condition have a normal life expectancy. There’s also evidence that an immune system gland Most people with MG are able to manage their called the thymus plays a role in MG. About 10-15 symptoms and lead active lives, and a few experience percent of people with MG have a thymic tumor, called a remission lasting many years. thymoma, and another 65 percent have overactive thymic cells, a condition called thymic hyperplasia. When the thymus doesn’t work properly, the immune system may lose some of its ability to distinguish self from non-self, making it more likely to attack the body’s own cells. MG affects both men and women and occurs across all racial and ethnic groups. It most commonly impacts young adult women (younger than 40) and older men (older than 60), but it can occur at any age, including during childhood. What are the signs and symptoms of MG? Myasthenia gravis weakens and fatigues the body’s voluntary muscles (those we can move at will). It doesn’t damage the musculature of the heart or the gastrointestinal tract. Skeleton and muscle • Muscle weakness • Partial paralysis of eye movements • Drooping of one or both eyelids Lungs • Blurred vision • Shortness of • Double vision breath • Change in facial expression • Difficulty chewing or swallowing • Impaired speech What should I know about MG? 1 The onset of myasthenia gravis 5 In generalized MG, weakness tends 9 Weakness and fatigue in MG tend may be sudden, and symptoms to spread sequentially from the face to fluctuate from day to day, and sometimes may not be immediately and neck to the upper limbs, the even during a single day. People identified as being caused by MG. hands, and then the lower limbs. with the disease are often strongest It may become difficult to lift the in the morning after a full night’s arms over the head, rise from a sleep, and weakest in the evening. 2 Early in its course, MG tends to sitting position, walk long distances, affect the muscles that control climb stairs, or grip heavy objects. movement of the eyes and eyelids, In some cases, weakness may 10 Over a longer term, the symptoms causing ocular weakness. spread to muscles in the chest of MG usually progress, reaching Consequently, a partial paralysis that control breathing. maximum or near-maximum of eye movements, double vision, severity within one to three and droopy eyelids are usually years of onset in most people. among the first symptoms of MG. 6 Sometimes the severe weakness of MG may cause respiratory 11 failure, which requires immediate Weakness serious enough to 3 Weakness and fatigue in the neck emergency medical care. require full-time wheelchair use is and jaw also can occur early in MG. not common in MG. Most people, This bulbar weakness — named for when properly treated, find they the nerves that originate from the 7 Many prescription drugs can can remain physically active. bulblike part of the brainstem — unmask or worsen symptoms of can make it difficult to talk, chew, MG. These include: muscle 12 Remission, a reversal of some or swallow, and hold up the head. relaxants used during surgery, all symptoms, occurs in about 20 aminoglycoside and quinolone percent of people with MG. Usually, antibiotics, cardiac anti-arrhythmics, the remissions are temporary, with 4 The degree of muscle weakness local anesthetics, and magnesium an average duration of five years, involved in MG varies greatly salts (including milk of magnesia). among individuals, ranging from but some experience more than a localized form limited to eye one remission during their lifetime. muscles (ocular myasthenia), to 8 Overexertion, emotional stress, A few individuals have experienced a severe or generalized form in infections (anything from tooth apparently permanent remissions which many muscles — sometimes abscesses to the flu), menstruation, lasting more than 20 years. including those that control and pregnancy also might lead to breathing — are affected. increased weakness in MG. How is MG treated? MEDICATIONS is a terminal complement inhibitor INTRAVENOUS THERAPY that targets a part of the immune system called the complement Medications to treat MG system, which is responsible for Plasmapheresis and intra- venous immunoglobulin are include anticholinesterase helping antibodies clear damaged agents, also called cholin- other therapies that may be cells and potentially toxic microbes esterase inhibitors, such as options in severe cases of that could cause infections. In mestinon or pyridostigmine, myasthenia gravis. Individuals which slow the breakdown of MG, antibodies whose job it is can have antibodies in their acetylcholine at the neuro- to target these toxic pathogens plasma (a liquid component muscular junction and thereby instead inappropriately recruit the in blood) that attack the NMJ. improve neuromuscular complement system and target the These treatments remove transmission and increase NMJ. Soliris is thought to work in the destructive antibodies, muscle strength. MG by inhibiting the complement although their effectiveness pathway to prevent destruction of usually lasts only for a few the NMJ. Treatment with Soliris weeks to months. will not cure generalized MG, but it may improve disease symptoms, the ability to carry out activities of daily living, and quality of life. SURGERY • Plasmapheresis is a procedure in which a machine is used to remove harmful antibodies in plasma and replace them Immunosuppressive drugs with good plasma or a plasma improve muscle strength by substitute. suppressing the production • Intravenous immunoglobulin of abnormal antibodies. They is a highly concentrated injection include prednisone, azathioprine, of antibodies pooled from many mycophenolate mofetil, tacrolimus, Thymectomy, an operation to healthy donors that temporarily and rituximab. remove the thymus gland, is changes the way the immune required in MG patients with system operates. It works by The US Food and Drug a thymic tumor and, in other binding to the antibodies that Administration (FDA) has cases, may lessen the severity approved eculizumab (brand name cause MG and removing them of MG symptoms. It may also Soliris), a type of complement from circulation. reduce the patient’s need for inhibitor, as a treatment for the use of additional drugs to Please talk to your medical provider to adults with generalized MG who obtain more information about potential control MG symptoms. are anti-acetylcholine receptor treatments for MG. antibody-positive. Soliris MDA Glossary Autoimmune disease Neuromuscular junction disorder A disease characterized by an A condition that is a result of the inappropriate attack of the immune destruction, malfunction, or absence system on the body’s own tissues of one or more key proteins involved in the transmission of signals between Diplopia muscles and nerves Double vision Neurotransmitter Dysarthria Chemicals that neurons, or brain cells, Difficulty speaking or forming words use to communicate information Dysphagia Ophthalmoparesis Difficulty swallowing Partial paralysis of eye movements Dyspnea Ptosis Difficulty breathing Drooping of one or both eyelids Genetic susceptibility Thymus An increased likelihood of developing a A gland, located in the chest behind particular disease based on a person’s the breast bone, that controls immune genetic makeup function and may be associated with myasthenia gravis Myasthenic crisis A medical emergency that occurs when the muscles that control breathing weaken to the point where individuals require a ventilator to help them breathe Neuromuscular junction The place where nerve cells connect with the muscles they control To learn more about MG, visit mda.org or contact the MDA National Resource Center at 833-ASK-MDA1 (275-6321).