Serum fibrinogen is not elevated in patients with myasthenia gravis

Myasthenia gravis (MG) is an autoimmune, autoantibody-mediated disease characterized by fatigable weakness of skeletal muscles. MG is a heterogeneous disease that currently lacks a robust biomarker for diagnosing all subtypes. Residual serum fibrinogen was found to be elevated 1000-fold in patients with MG in one study and posited to represent a universal diagnostic biomarker for MG. We set out to confirm elevated serum fibrinogen in patients with all subtypes of MG. We employed multiple methodologies to compare fibrinogen levels between MG patients and controls, using samples from independent cohorts. With enzyme-linked immunosorbent assay (ELISA), fibrinogen levels in sera from MG patients were not significantly different from controls. And in plasma samples, MG patients had a significantly lower amount of fibrinogen compared to controls. Using liquid chromatography-mass spectrometry (LC-MS), the abundance of serum fibrinogen-α was not elevated in patients compared to controls, and patients had a significantly lower abundance of serum fibrinogen-ß and fibrinogen-γ compared to controls. Our results do not support serum fibrinogen to be a diagnostic biomarker for MG and underscore the need for replication of novel findings to ensure our common goal of identifying effective biomarkers for MG.