Prevalence of Connective Tissue Disorder-Associated Interstitial Lung Disease Misdiagnosed and Treated As Tuberculosis

Introduction: Connective tissue disease-associated interstitial lung disease (CTD-ILD) is an important contributor to the burden of diffuse parenchymal lung disease in India. In tuberculosis-endemic regions, overlapping clinical and radiological features frequently result in misdiagnosis as pulmonary tuberculosis and exposure to empirical anti-tubercular therapy (ATT), leading to delayed initiation of appropriate treatment. Methods: We conducted a retrospective observational study of 17 patients diagnosed with CTD-ILD between July 2024 and July 2025 at a tertiary care center in Central India. Data collected included demographic characteristics, connective tissue disease subtype, high-resolution CT (HRCT) pattern, autoantibody profile, spirometry findings, prior exposure to anti-tubercular therapy, and treatment received. Results: The mean age was 52.7 years, with female predominance. Connective tissue disease subtypes included Sjögren syndrome (4/17, 24%), systemic lupus erythematosus (3/17, 18%), inflammatory myositis (3/17, 18%), systemic sclerosis (2/17, 12%), mixed connective tissue disease (3/17, 18%), and overlap syndromes (2/17, 12%). The HRCT patterns showed nonspecific interstitial pneumonia (NSIP) in 11/17 (65%), usual interstitial pneumonia (UIP) in 5/17 (29%), and lymphocytic interstitial pneumonia (LIP) in 1/17 (6%). All patients were positive for antinuclear antibodies, with disease-specific extractable nuclear antigen antibodies including Ro52, Jo-1, and Scl-70. Nine patients (9/17, 53%) had received empirical anti-tubercular therapy prior to diagnosis. Spirometry was available in 7/17 patients (41%); the median forced vital capacity was 75% of predicted, and the mean forced expiratory volume in one second to forced vital capacity ratio was 66%. Treatment included mycophenolate mofetil (9/17, 53%) and nintedanib (7/17, 41%), and one patient each received cyclophosphamide and rituximab, respectively. Conclusions: In this central Indian cohort, CTD-ILD most commonly presented with an NSIP pattern and was frequently misdiagnosed as tuberculosis, resulting in exposure to empirical anti-tubercular therapy. Early evaluation with HRCT and autoimmune serological testing is essential to ensure accurate diagnosis and timely initiation of appropriate immunosuppressive and antifibrotic therapy.