Correlation between muscle involvement, phenotype and D4Z4 fragment size in facioscapulohumeral muscular dystrophy

This study aimed to evaluate muscle involvement pattern and correlate the lesions on muscle imaging with clinical features and D4Z4 fragment size in 24 patients with facioscapulohumeral muscular dystrophy (FSHD). The grading of the muscle image detected by computed tomography (CT) was based on a four-point semi-quantitative visual scale. On muscle CT, the most affected muscle was trapezium, followed by hamstrings. CT image identified hamstrings involvement rather than shoulder-girdle in clinically asymptomatic subjects. CT image also showed that axial muscle was affected in one-third of patients which appeared even earlier than clinical manifestation. Strong correlations between CT findings, serum creatine kinase level and clinical severity scores were also found. Asymmetric involvement was more evident on CT image than it identified in manual muscle strength testing. Inverse correlation between CT grade and D4Z4 fragment size was clearly demonstrated. These findings suggest muscle CT will be helpful for the process of early intervention in FSHD, even in subjects in a preclinical status.