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DOI: 10.1055/s-0038-1626409
Neue Erkenntnisse bei der seronegativen generalisierten Myasthenia gravis
The seronegative generalized myasthenia gravisPublication History
Publication Date:
19 January 2018 (online)
![](https://www.thieme-connect.de/media/10.1055-s-00034916/200408/lookinside/thumbnails/10-1055-s-0038-1626409_de-1.jpg)
Zusammenfassung
Die generalisierte Myasthenia gravis (MG) ist eine Autoimmunerkrankung, die in 80-90% der Fälle durch pathogenetische Autoantikörper (AK) gegen nikotinerge Azetylcholinrezeptoren (AChR) gekennzeichnet ist. Bei einem Teil der Patienten mit AChR-AK-negativer generalisierter MG (so genannte seronegative MG) sind Autoantikörper gegen die muskelspezifische Rezeptor-Tyrosinkinase (MuSK) nachweisbar, die eine Rolle in der Anordnung der AChR während der Synapsenbildung spielt. Allerdings wird seit kurzem diskutiert, ob MuSK-AK lediglich ein Epiphänomen darstellen oder die Pathogenese hinreichend erklären können.
Eine MuSK-AK-positive MG ist häufiger bei Frauen. Die bulbäre und Atemhilfsmuskulatur ist häufig betroffen. MuSK-AK-positive Patienten scheinen weniger gut auf eine medikamentöse immunsuppressive Therapie anzusprechen als AChR-AK-positive. Eine gute Wirksamkeit wird durch Plasmapherese erzielt. Pathologische Thymusbefunde sind bei MuSK-AK-positiven Fällen deutlich seltener als bei AChR-AK-positiven. Bislang ist noch ungeklärt, ob die Thymektomie den Krankheitsverlauf bei MuSK-AK-positiven Patienten beeinflusst.
Weiterhin kann eine autoimmunvermittelte seronegative MG durch kongenitale Myasthenieformen mit späterem Manifestationsbeginn (Rapsyn-Mutationen, »slow-channel«-Syndrom durch AChR-Mutationen) vorgetäuscht werden.
Summary
Generalized Myasthenia gravis (MG) is an autoimmunmediated disorder, characterized in 80-90% by pathogenetic autoantibodies (Ab) against the nicotinergic acetylcholine receptor (AChR). In some patients with AChR-Ab-negative generalized MG (so-called seronegative MG) antibodies against the muscle-specific receptor tyrosin kinase (MuSK) were detected. MuSK plays a role in the clustering of AChR during synaptogenesis. It is not clear whether MuSK-Ab can sufficiently explain pathogenesis or whether they are just an epiphenomenon. MuSK-Ab-positive MG occurs more often in women. Bulbar and respiratory muscles are often involved. AChR-Abpositive patients seem to respond better to immunosuppressive therapy than MuSK-Ab-positive patients. Patients show short-time benefit after plasmapheresis. Pathological thymus findings are rarer in MuSK-Ab-positive than in AChR-Ab-positive cases. Therefore a favourable influence of thymectomy on the course of the disease seems to be less probable.
Additionally, congenital myasthenic syndromes with late onset (e.g. by rapsyn mutations, slow-channel syndrome by AChR mutation) can mimic an autoimmune mediated seronegative MG.
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