MUSK and rheumatoid arthritis: With the promising findings of the initial proteomic study with regards to the correlation of fibrinogens (Fig. 1) and MG diagnosis along with the result of the blinded study with fibrinogen-α (Fig. 3) we then conducted a validation study on a larger patient cohort consisting of sera from 31 MG patients (The serotype of each of these patients was initially blinded and revealed after the analysis was complete: 27 anti-AChR antibody positive, one anti-MuSK antibody positive, three seronegative), 18 from RA patients and 30 controls.