Interstitial Lung Disease in Patients with Mixed Connective Tissue Disease: A Retrospective Study.

Objective: To investigate the clinical features, severity and prognosis of interstitial lung disease (ILD) in patients with mixed connective tissue disease (MCTD). Methods: We performed a retrospective study on clinical data of MCTD patients admitted to China-Japan Friendship Hospital between October 2012 and October 2022. Data including long-term follow-up were retrieved from medical records. We compared MCTD patients with and without ILD in terms of clinical features, laboratory and imaging findings, severity and treatment response. Results: A total of 59 patients were included, with a mean age of 46 years, among which 91.5% (n = 54) were females. Symptoms of pulmonary involvement were present in 44 patients (74.6%, 95% CI: 62.3-84.9%). Based on lung high-resolution computed tomography (HRCT), ILD was diagnosed in 39 (66.1%) patients, among which 31 (79.5%) showed nonspecific interstitial pneumonia (NSIP) as the radiological pattern, 21 (53.9%) showed a reticulation pattern, while 24 (61.5%) showed ground glass opacity (GGO). Eight (13.6%) patients had pulmonary arterial hypertension (PAH), and 7 (11.9%) had pleural effusions. Based on pulmonary function tests (PFTs), 27 patients were divided into the mild 13 (48.1%) and moderate 14 (51.9%) groups. Multivariate analysis showed that gastroesophageal reflux (GER; OR=5.28, p=0.010) and cough (OR=4.61, p=0.043) were the predictive factors for ILD. With a median follow-up of 50 months, the mortality rate was 2.38%. Conclusion: ILD is common in MCTD patients, with NSIP as the common imaging pattern. Patients with GER and cough are relevant factors in the development of ILD. The majority of MCTD patients with ILD are mild to moderate in severity.