Quantitative magnetic resonance imaging (MRI) can identify muscle changes between patients with rheumatoid arthritis (RA) and healthy control participants; these changes may occur in patients with early RA, those with persistent active disease, and those who were in clinical remission, according to study results published in Rheumatology.

Previous studies have shown that RA is associated with altered body composition, including catabolic effects on skeletal muscle and rheumatoid cachexia. As limited data are available on the stage in which muscle involvement begins in patients with RA, the objective of the current study was to use quantitative MRI to estimate muscle involvement according to different stages of RA progression. Fat fraction, T2, mean diffusivity and fractional anisotropy were measured in the hamstrings and quadriceps.

The cross-sectional study included patients with RA from the Leeds Teaching Hospitals NHS Trust in Leeds, United Kingdom. Of 75 patients enrolled in the study, 27 were newly diagnosed RA, 13 had active RA, and 35 in clinical remission. Patients in all groups were age- and sex-matched with those in the active RA group. The final cohort included a total of 52 participants with 13 in each of the 3 RA groups and 13 in the healthy control group.


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Study results suggested significant differences between the 4 study groups in terms of T2, fat fraction, and muscle volume, but not in mean diffusivity or fractional anisotropy. Muscle T2 measurements were higher in all RA groups compared with the healthy control group, implying increased muscle edema and fatty infiltration in patients with RA. Muscle fat fraction was also higher in all RA groups compared with the healthy control group, suggesting fatty infiltration in patients with RA. Muscle volume was lower in all RA groups vs the healthy control group, suggesting muscle atrophy and decreased strength in patients with RA. While muscle volume was lower in all patients, including those were newly diagnosed and treatment-naive, the smallest difference was for those in clinical remission. Handgrip strength, knee extension, and flexion were lower in all 3 RA groups compared with the healthy control group.

Researchers reported that quantitative MRI and muscle strength measurements can be used to identify differences within the muscle between patients with RA and healthy control participants. The changes in muscle and strength occurred in early disease and were also evident in patients with RA in clinical remission.

The study had several limitations, including longer disease duration with increased risk for muscle deterioration in those with active drug-resistant RA, the small sample size, variation in shape and length of thigh muscles between patients, and lack of adjustment to additional potential confounders.

“This suggests that the muscles in patients [with] RA are affected in the early stages of the disease and that signs of muscle pathology and muscle weakness are still observed in clinical remission,” the researchers concluded.

Reference

Farrow M, Biglands J, Tanner S, Hensor EMA, Buch MH, Emery P, Tan AL. Muscle deterioration due to rheumatoid arthritis: assessment by quantitative MRI and strength testing. Rheumatology (Oxford). Published online September 10, 2020. doi: 10.1093/rheumatology/keaa364