Neurológia pre prax 5/2017

Myasthenia gravis with anti-MuSK antibodies

Myasthenia gravis is an autoimmune disease with formation of antibodies against the postsynaptic part of the neuromuscular junction. When the presence of anti-acetylcholine receptor antibodies is demonstrated, the condition is referred to as seropositive myasthenia gravis; when these antibodies are absent, it is seronegative myasthenia gravis. The anti-muscle-specific tyrosine kinase (MuSK) antibody was demonstrated in 35% (0–49%) of the seronegative forms. Anti-MuSK myasthenia gravis exhibits the following features: a predominance in women, earlier onset, characteristic clinical finding, and worse and inconstant response to treatment with cholinesterase inhibitors. With regard to neurophysiological tests, it is of importance to use repetitive stimulation to examine the proximal muscles (trapezius muscle, deltoid muscle) as well as the mimic muscles (nasalis muscle, orbicularis oculi muscle). With SF EMG (single-fibre EMG), there is a substantially higher positivity in examining the frontalis muscle or the orbicularis oculi muscle. Thymectomy is not indicated. Immunotherapy is effective – the administration of immunoglobulins, plasmapheresis, and corticosteroids in combination with other immunosuppressants. Myasthenia gravis with anti-MuSK antibodies is characterized by an unstable course, a higher frequency of myasthenic crises, and greater therapeutic complexity.

Keywords: myasthenia gravis, muscle-specific tyrosine kinase, electromyography, immunosuppression