myasthenia gravis

Myasthenia gravis

Myasthenia gravis (MG) is a long-term neuromuscular junction disease that leads to varying degrees of skeletal muscle weakness. The most commonly affected muscles are those of the eyes, face, and swallowing. It can result in double vision, drooping eyelids, and difficulties in talking and walking. Onset can be sudden. A small percentage of patients can have an enlarged thymus or rarely a thymoma. Myasthenia gravis is an autoimmune disease of the neuromuscular junction which results from antibodies that block or destroy nicotinic acetylcholine receptors (AChR) at the junction between the nerve and muscle. This prevents nerve impulses from triggering muscle contractions. Most cases are due to immunoglobulin G1 (IgG1) and IgG3 antibodies that attack AChR in the postsynaptic membrane, causing complement-mediated damage and muscle weakness. Rarely, an inherited genetic defect in the neuromuscular junction results in a similar condition known as congenital myasthenia. Babies of mothers with myasthenia may have symptoms during their first few months of life, known as neonatal myasthenia or more specifically transient neonatal myasthenia gravis. Diagnosis can be supported by blood tests for specific antibodies, the edrophonium test, electromyography (EMG), or a nerve conduction study. Mild forms of myasthenia gravis may be treated with medications known as acetylcholinesterase inhibitors, such as neostigmine and pyridostigmine. But these drugs only provide symptomatic relief. Therefore almost all patients will in addition require immunosuppressants, such as prednisone, mycopheno...