Anti-TRIM72 Autoantibodies in Idiopathic Inflammatory Myopathies

Background and PurposeTripartite motif-containing protein 72 (TRIM72) mediates tissue-repair following injury in several organs, including muscle and lung. Autoantibodies directed against TRIM72 (anti-TRIM72) have been identified in patients with idiopathic inflammatory myopathies (IIM) and disrupt TRIM72 function in vitro. We hypothesized that IIM patients positive for anti-TRIM72 antibodies would have a more severe clinical phenotype. MethodsSera from IIM patient (antisynthetase syndrome [ASyS], immune mediated necrotizing myopathy [IMNM], and dermatomyositis [DM]) and healthy controls (HC) were included. Anti-TRIM72 autoantibodies were tested using enzyme linked immunosorbent assay. Anti-TRIM72 testing was positive if value was >2 standard deviations above the mean for HC. Clinicodemographic features were identified through chart review and compared between anti-TRIM72 positive (anti-TRIM72[+]) and negative (anti-TRIM72[-]) groups. ResultsAnti-TRIM72 levels were significantly increased in patients with ASyS and IMNM when compared to patients with DM and healthy controls. Anti-TRIM72 levels were also increased in patients expressing anti-Jo-1, anti-PL7, anti-HMGCR, anti-SRP, and anti-MDA5. In ASyS, when anti-TRIM72(+) and anti-TRIM72(-) patients were compared, there were significantly more anti-TRIM72(+) ASyS patients with normal DLCO (>75%) when compared to anti-TRIM72(-); however, there were no differences in demographic features, CK levels or FVC. In anti-HMGCR(+) IMNM, anti-TRIM72(+) was associated with a lower proportion of females, as well as older age at time of diagnosis and at time of anti-TRIM72 testing; however, there was no significant difference in other clinicodemographic features in anti-HMGCR(+) IMNM patients when anti-TRIM72(+) and anti-TRIM72(-) groups were compared. ConclusionsAnti-TRIM72 antibody titres are increased in patients with ASyS and IMNM. The presence of anti-TRIM72 antibodies was not associated with a more severe phenotype in ASyS or anti-HMGCR(+) IMNM, and there were more ASyS patients with normal DLCO in the anti-TRIM72(+) group.