PURPOSE: To identify and validate serum biomarkers for the progression of 
Duchenne muscular dystrophy (DMD) using a MS-based bottom-up pipeline.
EXPERIMENTAL DESIGN: We used a bottom-up proteomics approach, including a 
protein concentration equalization step, different proteolytic digestions, and 
MS detection schemes, to identify candidate biomarkers in serum samples from 
control subjects and DMD patients. Fibronectin was chosen for follow-up based on 
the differences in peptide spectral counts and sequence coverage observed 
between the DMD and control groups. Subsequently, fibronectin levels were 
determined with ELISA in 68 DMD patients, 38 milder Becker muscular dystrophy 
patients, 33 patients with other neuromuscular disorders, and 15 age-matched 
adult and child controls.
RESULTS: There was a significant increase in fibronectin levels in DMD patients 
compared to age-matched controls. Fibronectin levels in patients with Becker 
muscular dystrophy, Bethlem myopathy, or myasthenia gravis were comparable to 
control levels. Progressive elevation in fibronectin levels was observed in 
longitudinal samples from 22 DMD patients followed up for a period of 6 months 
up to 4 years.
CONCLUSION AND CLINICAL RELEVANCE: This study suggests that serum fibronectin 
levels may constitute a promising biomarker to monitor disease progression in 
DMD patients.