Biomarker for Duchenne Muscular Dystrophy: An International, Multicenter, Observational, Longitudinal Protocol

Duchenne Muscular Dystrophy (DMD) is a devastating inherited neuromuscular disorder that affects 1 in 3300 live male births (females can be mildly affected carriers). DMD causes progressive weakness and loss of muscle mass, with symptoms usually appearing in early childhood. DMD arises from mutations in the DMD gene that codes for dystrophin.

The DMD gene is located on the short arm of chromosome X (locus Xp21) and codes for dystrophin, containing 3685 amino acid residues. 60-65% of DMD mutations are large dele-tions, 10-30% are nonsense and frame-shift mutations, 5-15% are duplications, and 2% are intronic or 5'- and 3'-UTR alterations.Dystrophin aggregates as a homotetramer in the skeletal muscles or associates with actin and Dystrophin-Associated Glycoproteins (DAGs), forming a stable complex that interacts with laminin in the extracellular matrix. Dystrophin is considered a key structural element in the muscle fiber, whose primary function is to stabilize plasma mem-brane, while the DAGs maintain the sarcolemmal stability by mediating the complex interactions of the muscle membrane and extracellular environment. The low levels of dystrophin lead to cellular instability and progressive leakage of intracellular components, explaining the characteristically high levels of creatine phosphokinase (CPK) in the blood of DMD patients.

Biomarkers serve as measurable indicators of normal biological or pathological processes. They are typically directly linked to genetic variants in specific genes and can predict, diagnose, monitor, and assess the severity of a disease. It is the goal of this study to identify, validate, and monitor biochemical markers from DMD affected participants.