Document resource
Introduction Interstitial lung disease (ILD) is a leading cause of death in both systemic sclerosis (SSc) and mixed connective tissue disease (MCTD). While clinical risk factors for ILD in SSc are well-characterized, MCTD lacks disease-specific ILD screening guidelines, and screening is often extrapolated from SSc. Whether ILD risk profiles in MCTD mirror those in SSc remains unclear. EMR-derived cohorts provide an opportunity to define ILD prevalence and associations in rare connective tissue diseases at scale.Material and Methods We conducted a retrospective cohort study of adults evaluated at UCLA Health between July 1, 2005, and July 1, 2025. Patients with MCTD were identified by ICD-10 codes (M35.1 or M35.9) in combination with anti-U1-RNP positivity, while patients with SSc were identified by ICD-10 code M34.9. For both diseases, inclusion required at least two documented visit diagnoses. ILD status was determined based on provider documentation. We examined clinical characteristics previously associated with ILD in SSc, and calculated odds ratios (ORs) with 95% confidence intervals (CIs) to assess associations. All analyses were performed in R (version 4.4.1).Results We identified 3988 SSc patients (2042 ILD, 51.2%) and 970 MCTD patients (301 ILD, 31.0%). SSc patients were older on average (62 vs. 49 years), while MCTD patients had higher BMI (26.3 vs. 24.6). Features associated with ILD in both diseases included pulmonary hypertension, gastroesophageal reflux disease (GERD), dysphagia, SSA positivity, and Hispanic ethnicity ( table 1). In MCTD, advancing age was strongly associated with ILD, particularly among patients aged >/= 55 years. In contrast, male sex and Black or Asian race were associated with ILD only in SSc, not in MCTD.Conclusions Given that ILD is a leading cause of death in both SSc and MCTD, recognizing disease-specific associations is key to improving early identification and therapeutic intervention. Since no ILD screening guidelines exist for MCTD, the present study suggests that certain clinical features may portend a higher risk of ILD in this population. As in SSc, MCTD-ILD was associated with pulmonary hypertension, GERD, dysphagia, SSA positivity, and Hispanic ethnicity. However, unlike SSc-ILD, male sex and Black race were not associated with ILD in the MCTD cohort, suggesting that these features should not be considered in ILD screening decisions. Importantly, ILD prevalence in MCTD may be underestimated, as CT-based screening is not standardized. EMR-based approaches represent an affordable and efficient strategy for studying rare diseases such as MCTD, and future prospective studies are needed to guide MCTD-specific ILD screening approaches.Abstract OC.27 Table 1Significant clinical characteristics associated with interstitial lung disease (ILD) in systemic sclerosis (SSc) and mixed connective tissue disease (MCTD)