Autoantibodies to muscle-specific tyrosine kinase

General Information

It is a second-line diagnostic test for myasthenia gravis when the results of first-line studies are negative.

Clinical information

Myasthenia Gravis Myasthenia Gravis is a neuromuscular disease characterized by progressive weakness and fatigue of voluntary (skeletal) muscles.

Diagnosis of the disease is based on clinical and electromyographic data. Positive serological data should be considered in the context of clinical, electromyographic, and anticholinesterase drug treatment results. Most cases are autoimmune and are caused by IgG autoantibodies that bind to critically important postsynaptic membrane proteins. The frequency of detection of auto-antibodies is lowest in patients with only extraocular muscle weakness. Detection of specific auto-antibodies is most frequent in the case of the generalized form of myasthenia gravis, although in some cases the generalized form is also seronegative (auto-antibodies do not develop).

Physiologically, muscle-specific tyrosine kinase is involved in the integration and stabilization of acetylcholine receptor clusters. Muscle-specific tyrosine kinase is a receptor that is activated by the release of agrin, a proteoglycan produced by the motor nerve. This process is necessary for the normal functioning of neuromuscular transmission.

When is the survey conducted?

For the diagnostics of myasthenia gravis when the results of first-line studies are negative.

Serial determination of muscle-specific tyrosine kinase is informative for monitoring the treatment of myasthenia gravis and for determining the correlation (correlation) of the autoantibody titer with the treatment and the clinical picture.

restriction

Against the background of immunosuppressive therapy, it is possible to get a false-seronegative response. Although muscle tyrosine kinase autoantibodies are specific for myasthenia gravis, its negative result does not exclude the diagnostics.

General serological (antibody) detection, in the context of a person's disease or family history, in 77% of cases allows the detection of autoimmune conditions, such as: thyroid diseases, type 1 diabetes, vitiligo, premature aging, rheumatoid arthritis, lupus, and others. In these pathologies, research may also reveal anti-nuclear antibodies, glutamate decarboxylase (GAD) antibodies, Thyroglobulin და Thyroperoxidase antibodies, Stomach parietal cells Antibodies and more.

Myasthenia gravis, with antibodies to the muscle-specific tyrosine kinase MuSK MG, is more common in women than in men. It develops at any age. Treatment with anticholinesterase drugs gives a certain (limited) effect. The thymus (breast gland) is usually normal, therefore thymectomy (excision of the breast gland) does not give a pronounced effect. Antibody titer lowering therapy is effective. Symptoms of facial, bulbar and respiratory muscle paralysis are manifested clinically, crises are frequent.

Material for examination: Venous blood

Referral norm:  ≤0.02 nmol/l

Interpretation:

A positive result of the study in correlation with clinical and anamnestic data confirms the diagnostics of myasthenia gravis with auto-antibodies of specific autoimmune muscle tyrosine kinase.

The seropositive rate of the study justifies immunosuppressive therapy.