Background/Purpose: Many connective tissue diseases are known to cause interstitial lung disease (ILD). American Indian/Alaska Native (AI/AN) populations have higher prevalence and severity of a number of connective tissue diseases that can be associated with ILD, but no previous  studies have examined the clinical characteristics of connective tissue disease-associated ILD (CTD-ILD) in AI/AN populations. We sought to describe the spectrum of CTD-ILD in the AI/AN population in Alaska.

Methods: Through this retrospective chart review conducted at the Alaska Native Medical Center, 45 AI/AN adults with a clinical diagnosis of CTD-ILD were identified.  A detailed medical record abstraction was performed for each potential case.  Clinical characteristics are reported, including demographics, underlying CTD, ILD subtypes, serologies, pulmonary function tests (PFTs) with changes over time, and medications prescribed.

Results: Underlying connective tissue disease diagnosis was heterogeneous in this population. Rheumatoid arthritis (RA) was the most common (n = 13), followed by systemic sclerosis (SSc, n = 12; limited cutaneous n = 7, diffuse cutaneous n = 5), and mixed connective tissue disease (MCTD, n = 9). The mean age at connective tissue disease diagnosis was 45 (standard deviation (SD) 15), and the mean age at ILD diagnosis was 52 (SD 14), for a mean time from CTD diagnosis to ILD diagnosis of 7 years. Most patients were diagnosed with usual interstitial pneumonia (UIP) by high resolution CT (HRCT) (60%). The baseline forced vital capacity (FVC) was 68 percent predicted, and fell by an average of 1.2 absolute percentage points per year. The baseline diffusing capacity of the lungs for carbon monoxide (DLCO) was 56 percent predicted and fell by an average of 5.1 absolute percentage points per year.

Conclusion: This study is the first to describe patterns of CTD-ILD in any AI/AN population. As in other populations, RA-ILD and SSc-ILD are common, but this population additionally had a high proportion of ILD associated with of MCTD. Understanding the clinical characteristics of CTD-ILD in this population may improve recognition and care of CTD-ILD in AI/AN people.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/connective-tissue-disease-related-interstitial-lung-disease-in-american-indian-alaska-native-people-in-alaska/