Distinct MR features in scleroderma associated myopathy

Objective: To compare the MRI features in patients with fibrosing [FM] versus non-fibrosing [NFM] systemic sclerosis [SSc]-associated myopathy. Methods: 10 patients with FM and 14 with NFM underwent bilateral thigh MRI [T1-weighted, STIR and DW/ADC mapping]. Three observers, blinded to histology evaluated 36 muscles per patient for presence of intramuscular edema, fascial edema, fatty replacement and atrophy and measured ADC values. Fisher's exact test and student’s t-test were used to compare MRI findings of FM [endomysial/ perimysial fibrosis] and NFM [necrosis/inflammation] on histology. Results: Intramuscular edema [p < 0.0001] and fascial edema [p = 0.07] were more common in FM. On DWI, elevated intramuscular signal was more common in FM, [low b-value: p < 0.0001 and high b-value: p < 0.0001]. On T1, NFM exhibited more fatty replacement [p = < 0.0001] and atrophy [p = < 0.0001]. Conclusions: Intramuscular and fascial edema on MRI are more common in SSc-associated FM, while markers of chronic muscle damage are more often associated with NFM.