Antisynthetase Syndrome Mimicking Pulmonary Infection: A Diagnostic Lesson From County-Managed Hospital.

Antisynthetase syndrome (ASS) is a rare chronic autoimmune disease classified as a distinct subtype of idiopathic inflammatory myopathy, characterized by the presence of anti-aminoacyl-transfer RNA synthetase (anti-ARS) antibodies. Typical clinical features include myositis, interstitial lung disease (ILD), arthritis, fever, mechanic's hands, and Raynaud's phenomenon, with a predominance in middle-aged to elderly females. We report an atypical case of a 75-year-old male presenting with a 6-month history of anorexia and fatigue, followed by a 3-week progression of chest tightness and dyspnea. Initially misdiagnosed as a pulmonary infection, the patient showed no improvement after two weeks of antimicrobial therapy. Diagnosis was ultimately confirmed through bronchoscopy and detection of anti-Jo-1 antibodies. Subsequent corticosteroid treatment led to complete radiographic resolution and significant clinical improvement. This case underscores the importance of considering ASS in elderly male patients to prevent misdiagnosis and ensure timely intervention.