Autoimmune-featured interstitial lung disease: a distinct entity

Abstract

Background: Patients with interstitial lung disease (ILD) may have features of an autoimmune disorder that do not meet the diagnostic criteria for connective tissue diseases. We determined the prevalence and characteristics of autoimmune-featured ILD (AIF-ILD) and compared these with those of idiopathic pulmonary fibrosis (IPF) and known connective tissue disease-related ILD (CTD-ILD).

Methods: Patients with ILD who did not meet the criteria for a connective tissue disease were defined as having AIF-ILD if they had a sign or symptom suggestive of a connective tissue disease and a serologic test reflective of an autoimmune process. Clinical characteristics, high-resolution CT images, and lung biopsy specimens were analyzed and compared with those of patients with IPF and CTD-ILD. Survival was evaluated using a Kaplan-Meier curve.

Results: Two hundred subjects completed the questionnaire and serologic testing. AIF-ILD was identified in 32%, IPF in 29%, and CTD-ILD in 19%. Gender, age, and race differed among groups (P < .01). Sixty-two percent of patients with AIF-ILD had a typical usual interstitial pneumonia (UIP) pattern on CT images. In 31 patients with AIF-ILD, lung biopsy specimens showed UIP in 81% and nonspecific interstitial pneumonia in 6%. Patients with AIF-ILD and IPF had similar survival, worse than those with CTD-ILD (P < .01). Antinuclear antibody (ANA) titers ≥ 1:1280 were associated with improved survival in patients with AIF-ILD (P = .02).

Conclusions: Systematic evaluation of symptoms and serologic tests in ILD can identify AIF-ILD. A UIP pattern on CT images and histopathology is common in AIF-ILD. Although survival for patients with AIF-ILD is poor, ANA titers ≥ 1:1280 are associated with improved survival.

Figures

Figure 1.

Flow diagram detailing the distribution of radiographic and pathologic findings in study subjects. A, AIF-ILD. B, IPF. C, CTD-ILD. AIF-ILD = autoimmune-featured interstitial lung disease; CTD-ILD = connective tissue disease-associated interstitial lung disease; Dlco = diffusion capacity of the lung for carbon monoxide; IPF = idiopathic pulmonary fibrosis; NSIP = nonspecific interstitial pneumonia; UIP = usual interstitial pneumonia.

Figure 2.

Comparison of the survival curves for subjects with AIF-ILD, IPF, and CTD-ILD. Subjects with CTD-ILD had improved survival compared with either subjects with AIF-ILD or those with IPF (P < .01). PFT = pulmonary function test. See Figure 1 legend for expansion of other abbreviations.

Figure 3.

Comparison of the survival curves by antinuclear antibody (ANA) titer for subjects with AIF-ILD. Subjects with AIF-ILD with an ANA titer ≥ 1:1280 had improved survival compared with those with an ANA titer P = .02). See Figure 2 legend for expansion of other abbreviation.