What's myasthenia gravis?
Myasthenia gravis is an autoimmune disease that affects the transmission of signals from nerves to muscles. The name myasthenia gravis comes from Greek and Latin words meaning "grave muscle weakness." Today, however, most cases of myasthenia gravis are not as "grave" as the name implies. In fact, most people with myasthenia gravis can expect to live normal or nearly normal lives. The hallmark of myasthenia gravis is muscle weakness that increases during periods of
activity and improves after periods of rest. Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often, but not always, involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.
Myasthenia gravis is a disorder of neuromuscular transmission leading to fluctuating weakness and fatigue. It is one of the best known autoimmune disorders and the antigens and disease mechanisms have well been identified. Weakness is caused by circulating antibodies that block acetylcholine receptors at the neuromuscular junction. A myasthenic crisis may give rise to a generalized paralysis and assisted ventilation may be required to sustain life. Acetylcholine is a chemical substance that sustains muscle contraction by stimulating the muscle fibers by binding to its receptors. The immunologic reaction against these receptors and consecutive damage of the neuromuscular endplate give rise to deficient stimulation of muscle fibers. Patients frequently present with restricted movements of eye muscles and eyelids, difficulty swallowing and speaking, generalized weakness and fatigue. Myasthenia gravis is usually treated with cholinesterase inhibitors, immunosuppressive drugs, thymectomy and plasma exchange. Although the term gravis means grave, recent developments in disease treatment have made the prognosis more favourable. However a considerable portion of patients still find it necessary to seek admission to the intensive care units for assisted ventilation.
Myasthenia gravis typically strikes muscles in the face first. Muscles that control the eyelids and eye movements usually are affected early in the disease. Later, facial weakness can make smiling, chewing, swallowing and talking difficult. In most people, the disease eventually becomes more generalized and can affect the muscles of the arms and legs. Sometimes, the disease affects the muscles that control breathing. In some situations, such as during a respiratory infection, this weakness could lead to a myasthenic crisis during which the person may need help to breathe. myasthenia gravis may be associated with other autoimmune diseases. Patients with family members who suffer from disorders such as rheumatoid arthritis, scleroderma, and lupus may have an increased risk for myasthenia gravis.