Anti-synthetase Syndrome Overlapping with Systemic Lupus Erythematosus: A Diagnostic Dilemma

Anti-aminoacyl-tRNA synthetase antibodies are observed in 30% of patients with anti-synthetase syndrome (ASTS), an inflammatory myopathy. We present a case of ASTS in a middle-aged male with an early manifestation of interstitial lung disease. The patient had a history of organizing pneumonia, diagnosed via imaging and lung biopsy. He was prescribed steroids for 10 months and was referred to the rheumatology clinic for evaluation of possible connective tissue disease. Initial workup and clinical presentation suggested a diagnosis of systemic lupus erythematosus. However, during the follow-up, mechanic’s hands, lung fibrosis progression, and the presence of anti-JO-1 and anti-PL-7 antibodies were noted. After systemic immunosuppressant treatment, the patient showed favorable clinical and laboratory responses. ASTS constitutes a diagnostic challenge since the classical clinical manifestations may not present initially and can overlap with other rheumatic diseases. Future studies are needed to accurately diagnose ASTS and to evaluate the efficacy of treatment.