Cytomegalovirus Pneumonia Requiring Intensive Care During Treatment for Rapidly Progressive Interstitial Lung Disease Associated With Anti‐Synthetase Syndrome: A Case Report

A 70-year-old man presented with fever and malaise and was diagnosed with anti-synthetase syndrome based on chest computed tomography and laboratory findings. Steroid therapy was initiated because of progressive respiratory failure. However, despite steroid therapy, his respiratory status worsened, accompanied by expansion of ground-glass opacities (GGOs) on imaging. On hospital day 26, the patient developed severe respiratory failure, requiring mechanical ventilation and prone positioning, at which time cytomegalovirus (CMV) antigenemia was detected. After clinically diagnosing CMV pneumonia superimposed on interstitial lung disease (ILD), ganciclovir was initiated while gradually tapering corticosteroid therapy. This approach led to significant clinical and radiological improvements. The patient was successfully weaned from ventilation on day 30 and discharged on day 70. In patients with rapidly progressive ILD who deteriorate despite high-dose corticosteroids and develop new diffuse GGOs, superimposed CMV infection should be suspected and promptly evaluated. Early recognition and antiviral therapy are essential for improving outcomes.