MuSK antibody positive myasthenia gravis

Original Article

J Korean Assoc EMG Electrodiagn Med 2012;14(1):10-16.
Published online June 1, 2012.

Received: 20 April 2012 • Revised: 26 April 2012 • Accepted: 26 April 2012

Abstract

Since Hoch et al reported the presence of antibodies to muscle specific receptor tyrosine kinase (MuSK) in seronegative myasthenia gravis (MG), MG with MuSK antibodies (MuSK-MG) has been reported to have unique clinical features, diagnostic problems and response to treatment. Patients with MuSK-MG have a tendency of early and frequent involvement of bulbar muscles, often associated with prominent facial or tongue atrophy. Diagnostic yields of edrophonium test, and electrophysiologic tests, such as repetitive nerve stimulation test (RNS) and single fiber electromyography (SFEMG) are lower than in patients with acetylcholine receptor antibodies (AChR-MG). When doing edrophonium test or treating with acetylchoinesterase inhibitors, they often show intolerance (muscarinic and nicotinic side effects) and even show worsening of muscle weakness (hypersensitivity). However, because most of studies included small numbers of MuSK-MG patients, there have been some discrepancies among reports. And there have been questions about pathogenesis of MuSK antibodies to induce muscle weakness. I would like review the pathogenesis, clinical features, diagnosis, and treatment of MuSK-MG

Key Words: muscle specific receptor tyrosine kinase, seronegative myasthenia gravis, pathogenesis