Whole Body Phase Angle as a Promising Marker of Disease Severity in Facioscapulohumeral Muscular Dystrophy

Introduction/Aims: To investigate its potential role as a marker of disease severity in facioscapulohumeral dystrophy (FSHD), this study examined the association between whole- body phase angle (PhA) and clinically assessed severity in FSHD patients. Methods: Patients were evaluated for PhA using bioelectrical impedance analysis (BIA) and for disease severity using the FSHD clinical score. In a subgroup, physical activity level (PAL) was assessed using a questionnaire. Pearson correlations were performed in the total cohort and PAL- assessed subgroup, stratified by sex and clinical phenotype (category A and non- A) according to the Comprehensive Clinical Evaluation Form. Multivariate regression analyses were conducted adjusting for age, body mass index, and PAL. Due to the small sample, correlation was not performed in PAL- assessed non- A patients, while multivariate regression was not performed in non- A patients and PAL- assessed stratified subgroups. Results: Seventy- two patients (mean age 39.94 ± 17.52 years; 27 females and 45 males; 58 category A and 14 non- A) were enrolled. The PAL- assessed subgroup comprised 38 patients (mean age 41.39 ± 14.98 years; 16 females and 22 males; 31 category A and 7 non- A). Pearson analyses revealed that PhA was inversely associated with clinical score in all groups (r –0.63 to –0.84, p 0.02 to < 0.001). Multivariate regression confirmed PhA as the sole independent predictor across all groups (β = –0.64 to –0.93, all p < 0.001). Discussion: These results support the potential role of PhA as a marker of disease severity in FSHD. Longitudinal studies are warranted to determine its sensitivity for monitoring disease progression over time.