Tocilizumab Treatment in a Patient of Refractory Anti-EJ Positive ASyS: A Case Report

Anti-synthetase syndrome (ASyS) is an autoimmune disease characterized by the presence of autoantibodies to aminoacyl-tRNA synthetases accompanied with various organ involvements, including the lung, joints, and skin. The ASyS-related interstitial lung disease (ILD) can be seen in the vast majority of patients. The extent of lung involvement has a significant impact on patient prognosis; the occurrence of rapid-progressive ILD could prominently increase mortality. The mainstay of treatment is prednisone in combination with conventional synthetic disease-modifying anti-rheumatic drugs or some biologic disease-modifying anti-rheumatic drugs (DMARDs). Tocilizumab (TCZ), a recombinant humanized anti-interleukin (IL)-6 receptor monoclonal antibody, has also been used to treat some systemic autoimmune rheumatic diseases associated with ILD. Although the most recent American College of Rheumatology (ACR) Guideline for the Treatment of Interstitial Lung Disease conditionally recommends against the use of TCZ as a treatment option for people with idiopathic inflammatory myopathy (IIM)-ILD progression despite initial ILD treatment, the treatment effect of TCZ in ASyS patients remains obscure, particularly for refractory cases with anti-non-Jo1 antibodies. This report describes a case of Chinese ASyS patients with anti-EJ-positive antibodies who presented with typical proximal muscle weakness, elevated creatine kinase, and ILD with non-specific interstitial pneumonia (NSIP) pattern, along with typical skin involvement such as mechanic's hand. The patients were resistant to various treatments, including rituximab (RTX), but benefited from TCZ. In this case, TCZ shows good therapeutic efficacy in a fatal acute exacerbation of ILD with a hyperinflammatory status, resulting in a relative remission of the disease flare and full preservation of lung function with a positive long-term treatment outcome.