Metabolic and structural skeletal muscle health in systemic lupus erythematosus related fatigue: a multi-modal magnetic resonance imaging study.

Objective To investigate the potential structural and metabolic role of skeletal muscle in systemic lupus erythematosus (SLE)-related fatigue. Methods A case-control, multimodal magnetic resonance imaging (MRI) study was conducted. Cases were patients with inactive SLE who reported chronic fatigue. Controls were age- and sex-matched healthy members of the general population. Patients were clinically characterized and then underwent a 3T whole-body MRI scan. Resting and dynamic P-31 MRI spectroscopy of the calf muscles was applied, from which phosphocreatine (PCr) recovery halftime, a marker of mitochondrial dysfunction, was computed. In addition, microstructural sequences (T1-weighted anatomic images, T2 mapping, and diffusion tensor imaging) were acquired. Descriptive statistics evaluated group differences and within-case physical fatigue correlations were explored. Results Of the 37 recruits (mean age 43.8 years, 89.2% female), cases (n = 19) reported higher levels of physical fatigue, pain, depression, and sleep disturbance compared to the control group (P < 0.0001). PCr was greater (P = 0.045) among cases (mean +/- SD 33.0 +/- 9.0 seconds) compared to controls (mean +/- SD 27.1 +/- 6.6 seconds). No microstructural group differences were observed. Within cases, physical fatigue did not correlate with PCr (r = -0.28, P = 0.25). Conclusion We report preliminary data demonstrating greater skeletal muscle mitochondrial dysfunction among fatigued patients with SLE compared to healthy controls.