High prevalence of necrotising myopathy pattern in muscle biopsies of patients with anti-Jo-1 antisynthetase syndrome.

Abstract

Until now, researchers have not provided a well-defined muscle histological pattern for antisynthetase syndrome (ASSD). Therefore, we aimed to analyse the muscle biopsies of patients with anti-Jo-1 ASSD. This study included 26 patients with anti-Jo-1 ASSD admitted for investigation of the disease and obligatorily with muscle impairment, from 2010 to 2021, whose serial frozen muscle sections were analysed. Patients' mean age at disease diagnosis was 42.8±11.6 years, and the female gender was most predominant. Concerning muscle biopsies, cell infiltrates were present in 76.9% of the samples, and they were mainly located at the endomysium area (70%), with a predominance of macrophages (92.9%). Fiber muscle necrosis was present in 92.3% and was diffused in 54.2%. Expression of MHC-I was seen in all samples. Samples were mostly marked by the presence of CD68+ and discreet/low CD4+ and CD8+ staining, which is consistent with a higher predominance of observed necrosis and macrophage cell infiltrates. In general, 38.5% of patients had a necrotising myopathy pattern in muscle biopsies, whereas 34.6% and 26.9% had a general inflammatory myopathy pattern and nonspecific myopathy, respectively. This necrotising myopathy pattern was not associated with the demographic, clinical, or laboratory data. Our data show that almost 40% of patients with well-defined anti-Jo-1 ASSD with objective muscle impairment have a necrotising myopathy pattern in their muscle biopsies. Although this pattern is more classically related to immune-mediated necrotising myopathies, in association with clinical manifestations and the presence of anti-Jo-1 autoantibodies, this characteristic may lead to ASSD diagnosis.