Disease specific enrichment of circulating let-7 family microRNA in MuSK+ myasthenia gravis

Myasthenia gravis (MG) patients with antibodies against the muscle specific tyrosine kinase (MuSK +) have predominantly involvement of cranio-bulbar muscles and do not display thymus pathology, as do acetylcholine receptor antibody seropositive (AChR +) MG patients. In search of novel biomarkers for MuSK + MG, we evaluated circulating serum microRNAs. Four analyzed microRNAs were specifically elevated in MuSK + MG patient serum samples: let-7a-5p, let-7f-5p, miR-151a-3p and miR-423-5p. The circulating microRNA profile in MuSK. + MG differs from the profile previously observed in the serum of AChR + MG, thus indicating the etiological difference between these two entities. We propose that the identified microRNAs could serve as potential serum biomarkers for MuSK + MG.