Abstract
Myasthenia gravis is an autoimmune disease with formation of antibodies against the postsynaptic part of the neuromuscularjunction. When the presence of anti-acetylcholine receptor antibodies is demonstrated, the condition is referred to as seropositivemyasthenia 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 followingfeatures: a predominance in women, earlier onset, characteristic clinical finding, and worse and inconstant response to treatmentwith cholinesterase inhibitors.
With regard to neurophysiological tests, it is of importance to use repetitive stimulation to examinethe 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 oculimuscle. Thymectomy is not indicated.
Immunotherapy is effective - the administration of immunoglobulins, plasmapheresis, andcorticosteroids in combination with other immunosuppressants. Myasthenia gravis with anti-MuSK antibodies is characterizedby an unstable course, a higher frequency of myasthenic crises, and greater therapeutic complexity.