The differing patterns of interstitial lung involvement in connective tissue diseases

Area of Science:

• Pulmonary Medicine
• Rheumatology
• Data Science

Background:

• Connective tissue disorders (CTD) frequently lead to pulmonary complications.
• Diagnostic challenges have historically hindered the clear delineation of these lung issues.
• A novel clustering approach offers a new perspective on understanding CTD-related lung disease.

Purpose of the Study:

• To apply a clustering method to categorize pulmonary complications in patients with CTD.
• To assess the nature and extent of lung involvement in a large CTD cohort.
• To identify distinct patient profiles based on respiratory function and inflammatory markers.

Main Methods:

• Utilized an 8-investigation data-driven clustering method.
• Classified patients into four distinct categories: normal non-smoker, normal smoker, active interstitial lung disease, and bronchiolitis.
• Analyzed respiratory variables, bronchoalveolar lavage (BAL) cell counts, and gallium index.

Main Results:

• Cluster 1: Normal non-smokers with no active lung disease.
• Cluster 2: Smokers with normal respiratory function but altered BAL cell counts (increased macrophages, decreased lymphocytes) and mild DLCO reduction.
• Cluster 3: Active interstitial lung disease characterized by severely reduced DLCO, elevated gallium index, BAL cell counts, and inflammatory markers (neutrophils, lymphocytes), with potential lymphocytic or neutrophilic alveolitis subgroups.
• Cluster 4: Bronchiolitis indicated by reduced maximal mid-expiratory flow rate and elevated BAL lymphocyte percentage and gallium index.

Conclusions:

• The clustering method effectively delineates pulmonary complication patterns in CTD.
• Sjögren's syndrome appears most frequently associated with pulmonary disease within the CTD spectrum.
• The findings provide a framework for better understanding and potentially managing lung involvement in CTD.