Fat-Fraction Quantification Using Three-Point Dixon Technique in Duchenne Muscular Dystrophy and Its Correlation With Clinical Progression and Genotypic Characteristics: A Single Centre One-Year Prospective Study.

INTRODUCTION/AIMS: Muscle fat fraction (MFF) quantification using the Dixon magnetic resonance imaging (MRI) technique is an emerging objective, non-invasive biomarker in Duchenne muscular dystrophy (DMD). This study aimed to evaluate the relationship between MFF and disease progression, specifically its correlation with functional decline and genotypic characteristics.

METHODS

In this single-center prospective observational study, genetically confirmed, independently ambulant boys with DMD underwent MFF quantification of pelvic and thigh muscles. Functional measures including Medical Research Council (MRC) sum score, North Star Ambulatory Assessment (NSAA), and six-minute walk test (6MWT) were assessed at baseline, 6, and 12 months.

RESULTS

Forty boys (median age 8 years) were included. Highest mean MFF was observed in gluteal muscles (51.74% ± 23.26 right; 50.29% ± 24.07 left), while hamstrings showed the lowest. MFF demonstrated strong inverse correlations with all functional measures across most muscle groups at all time points. Baseline quadriceps MFF showed the strongest correlation with rate of decline of 6MWT over 1 year (r = 0.668 (CI 0.450, 0.811) and r = 0.564 (CI 0.307, 0.745) for right and left respectively). Adductor MFF was significantly higher in proximal versus distal variants (p = 0.049 and p = 0.037).

DISCUSSION: Baseline MFF, particularly in quadriceps, predicts functional decline in ambulatory DMD. Genotype-specific adductor involvement suggests novel, variant-specific spatial differences in muscle involvement. Longitudinal studies integrating genotype-phenotype analyses could validate MFF as a biomarker for clinical trials.