Sarcopenia in Rheumatoid arthritis. A narrative review

Abstract

Sarcopenia was recently identified as an entity in the ICD-10 classification of October 2016. According to the recommendation of the European Working Group on Sarcopenia in Older People (EWGSOP2), sarcopenia is defined as low muscle strength and low muscle mass, while physical performance is used to categorize the severity of sarcopenia. In recent years, sarcopenia has become increasingly common in younger patients with autoimmune diseases such as Rheumatoid arthritis (RA). Due to the chronic inflammation caused by RA, patients have reduced physical activity, immobility, stiffness, and joint destruction and all of that lead to the loss of muscle mass, muscle strength, disability and significantly lowering the patients' quality of life. This article is a narrative review about sarcopenia in RA, with a special focus in its pathogenesis and management.

Keywords: Autoimmune disease; Inflammation; Rheumatoid arthritis; Sarcopenia.

Figure 1

Flow diagram of search results.

Figure 2

Mechanisms of sarcopenia and metabolic modifications in rheumatoid arthritis (by An HJ et al.[36] published under CC BY 4.0 license) IGF-1, insulin-like growth factor-1; IGFBP, insulin-like growth factor binding protein; IL-1, interleukin-1; TNF-α, tumor necrosis factor-α; GC, glucocorticoid; GR, glucocorticoid receptor; gp 130, glycoprotein 130; Pax7, paired box 7; PI3K, phosphoinositide 3-kinase; mTOR, mammalian target of rapamycin; MAPK, mitogen-activated protein kinase; IKK, IκB kinase; IκB, inhibitor of nuclear factor kappa B; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; JAK, Janus kinase; STAT3, signal transducer and activator of transcription 3; MuRF-1, muscle RING-finger 1; UPS, ubiquitin proteasome system.

Figure 3

Mechanisms of treatment in RA patients. Biologic DMARDs (bDMARDs), targeted synthetic DMARDs (tsDMARDs), conventional synthetic DMARDs (csDMARDs).