Ro52, Myositis, and Interstitial Lung Disease

Ro52 is a member of the tripartite motif-containing (TRIM) family and, hence, is also known as TRIM21. Ro52 is distinct, with no structural homology to Ro60 (also known as TROVE2),1 although both are major targets of autoantibody responses in several autoimmune connective tissue diseases (CTDs). Indeed, early studies describing anti-Ro (SSA) do not make a distinction between the separate autoantibody specificities, although they frequently coexist in conditions such as systemic lupus erythematosus (SLE) and Sjögren syndrome (SS) and are often accompanied by anti-La (SSB). However, there is compelling evidence that the separate measurement of anti-Ro52 adds important information concerning patient management and outcomes, not least in idiopathic inflammatory myopathy (IIM) and interstitial lung disease (ILD). In the context of IIM, anti-Ro52 is regarded as a myositis-associated autoantibody (MAA) and can be found in other CTDs including SLE, SS, systemic sclerosis (SSc), and mixed CTD (MCTD). In contrast, myositis-specific autoantibodies (MSAs) are uncommonly encountered in other conditions apart from IIM and rarely coexist in the same patient.2 An important point to note is that MSAs may occur in some manifestations of the IIM spectrum, such as in ILD or in clinically amyopathic dermatomyositis (CADM) without any apparent muscle involvement, and arguably should be redesignated as myositis spectrum autoantibodies. For instance, some of the rarer anti-tRNA synthetase autoantibodies (anti-PL7 and anti-PL12) may be found in patients with ILD alone, or where ILD is the major disease manifestation.3 The … Address correspondence to Dr. N.J. McHugh, University of Bath, Bath, BA2 7AY, UK. Email: N.J.McHugh{at}bath.ac.uk.