Anti-MuSK antibody levels don’t reflect MG disease severity: Study
Researchers say antibodies 'not suitable' as biomarkers for severity, prognosis
Levels of antibodies against muscle-specific kinase (MuSK) are not reflective of disease severity in people with MuSK-positive myasthenia gravis (MG), according to a study.
“Given our results, MuSK autoantibodies are not suitable as biomarkers for clinical severity or prognosis in MuSK-positive MG,” the researchers wrote.
The study, “Prevalence and course of muscle-specific receptor tyrosine kinase (MuSK) antibodies in myasthenia gravis – A retrospective study,” was published in the Journal of the Neurological Sciences.
MG is an autoimmune disease usually driven by autoantibodies that disrupt the communication between nerve and muscle cells, ultimately leading to the disease’s hallmark symptoms of muscle weakness and fatigue.
The most common type of MG-driving autoantibodies target a protein called acetylcholine receptor. Autoantibodies targeting the protein MuSK are a less common and less well-understood cause of MG.
Anti-MuSK antibodies and disease severity
Some studies have reported that titers (levels) of anti-MuSK autoantibodies are associated with disease severity in people with MuSK-positive MG, while other studies have found no such association.
Seeking to gain greater clarity into the association between anti-MuSK autoantibody titers and disease severity, researchers in Germany analyzed 749 blood samples collected from 641 people with MG over the course of at least 10 years.
Twenty-one of those samples from seven patients were positive for anti-MuSK autoantibodies.
The researchers performed statistical analyses looking for correlations between anti-MuSK autoantibody titers and disease severity, as measured by the Besinger score, an early version of what came out to be the Quantitative MG score, a widely used measure of MG severity.
Results showed that there was no meaningful association between anti-MuSK autoantibody titers and disease severity scores.
The researchers also found 78 samples from 73 patients that had relatively high levels of anti-MuSK autoantibodies. The antibodies were technically detectable, but their levels were not high enough for the samples to be considered to be MuSK-positive. The scientists said they found no substantial association between the presence of these elevated but “formally negative” anti-MuSK autoantibodies and disease features.
“In contrast to other studies, we could not establish an association between autoantibody titers and the clinical severity of MG, as measured by the Besinger score,” the researchers wrote. “Also, elevated but formally negative MuSK autoantibodies probably have no clinical significance, as we could not find an association with MG or any other autoimmune disease.”
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