Oxygen-Dependent Patient with Antisynthetase Syndrome Associated Interstitial Lung Disease Responds Promptly to Rituximab with Rapid Pulmonary Function Improvement.

Antisynthetase syndrome (anti-SS) is a rare systemic autoimmune disorder characterized by myositis, Raynaud's phenomenon, fever, interstitial lung disease (ILD), polyarthralgia, and presence of antibodies against tRNA synthetase, especially anti-Jo-1. Rarely, anti-SS can present as isolated ILD, with clinical features very similar to atypical pneumonia, making diagnosis extremely challenging. We report a patient originally diagnosed with atypical pneumonia, requiring oxygen supplementation, who failed treatment with antibiotics. Radiological findings were suspicious for ILD and a comprehensive rheumatological work-up revealed the diagnosis of anti-SS associated ILD. Prompt treatment was initiated with steroids and rituximab. Follow up pulmonary function tests showed an improvement in her diffusing capacity of the lung for carbon monoxide and forced vital capacity allowing her to resume her daily life without supplemental oxygen.