Based on observations in our well-established mouse model of HRS (histidyl-tRNA synthetase)-induced myositis (14–16) in which mice immunized with recombinant HRS (Jo-1) protein develop anti-Ro60 as well as anti-Ro52 antibodies, we sought to define the prevalence of anti-Ro60 antibodies (with/without co-existing anti-Ro52 antibodies) and corresponding clinical features in humans with anti-Jo-1 antibody-positive anti-synthetase syndrome. Here, TRIM21 is linked to myositis disease.