Myasthenia Gravis

Myasthenia gravis (MG) is a rare autoimmune neuromuscular junction (where a nerve cell meets a muscle cell) disorder caused as a result of problems in the transmission of nerve signals to muscles. MG is primarily characterized by muscle weakness and muscle fatigue. In general population MG affects 10 - 20 in 1,00,000 (approaching 0.02%) people.

Normally, nerve endings release a substance, called acetylcholine, which binds to receptors, called acetylcholine receptors, on muscles. That binding signals muscles to contract. In an MG person, body's own immune system makes blocking molecules, known as antibodies, to block binding signal. In other words MG interferes with messages nerves send to muscles. Common symptoms are trouble with vision (diplopia) and eyelid movement (ptosis), facial expression and swallowing (dysphagia) and general muscle fatigue.

Treatment may include symptomatic treatment with cholinesterase inhibitors and modulation of the immune system with corticosteroids etc. Improvement may be achieved with plasma exchange or intravenous immunoglobulin in specific cases. Removal of thymus gland (thymectomy) is also an option.

As back as 17th century there were a few reports of heavy eye lids and fatiguable weakness. Nineteenth century witnessed modern description of myasthenic symptoms. In 1930s thymectomy was established as an effective treatment for MG.

Contributor: Duraiswamy Navaneetham PhD.

Temple University School of Medicine

Philadelphia, PA, USA

October 2009