Chromosome 4q D4Z4 contraction status in Turkish patients with facioscapulohumeral muscular dystrophy

Purpose: This study aimed to provide an updated overview of the genetic and clinical features of patients with facioscapulohumeral muscular dystrophy1 (FSHD1) followed between 2006 and 2025 in the Mediterranean region of Turkey. Materials and Methods: A total of 46 patients diagnosed as having FSHD1 through Southern blot analysis were included. The cohort consisted of 26 males and 20 females, with a mean age of 32.93 ± 17.01 years. Clinical severity scores (CSS) and age-corrected CSS (ACSS) were assessed based on neurologic examinations. Results: The most frequent D4Z4 repeat size was 4 units (30.4%). Although CSS and ACSS appeared lower in female patients, the difference was not statistically significant. Patients aged under 30 years exhibited significantly lower CSS and ACSS compared with those aged over 30 years. A strong correlation was observed between age and both CSS and ACSS; no significant correlation was found between D4Z4RU and clinical severity. Among the 46 patients, 20 families were represented, and one patient had a de novo mosaic mutation. Conclusion: Our findings highlight the importance of longitudinal and population-specific data in understanding FSHD. Increased molecular diagnosis and regular follow-up of patients may facilitate future research and the development of targeted therapies.