A Multicenter Registry for Rare Interstitial Lung Diseases in Korea: Baseline Characteristics and Clinical Outcomes

Rare interstitial lung diseases (ILDs) are a heterogeneous group of diffuse parenchymal lung disorders with low prevalence and diverse etiologies that pose diagnostic and therapeutic challenges. We aimed to establish a nationwide, multicenter registry of rare ILDs in South Korea to characterize their clinical features and outcomes.

We conducted a multicenter, observational cohort study involving 304 patients with rare ILDs including Birt-Hogg-Dubé syndrome (BHD), lymphangioleiomyomatosis (LAM), pulmonary alveolar proteinosis (PAP), pulmonary Langerhans cell histiocytosis (PLCH), pleuroparenchymal fibroelastosis (PPFE), and hypersensitivity pneumonitis (HP) enrolled across 20 centers in Korea between September 2023 and December 2024. Data on clinical characteristics, outcomes, and treatment were collected.

LAM (28.3%) and PAP (26.6%) were the most prevalent, followed by BHD (18.1%), PLCH (13.2%), HP (7.6%), and PPFE (6.3%). Dyspnea was common in HP and PPFE, whereas BHD and LAM were often asymptomatic. Pneumothorax was frequent in BHD (44.6%) and LAM (11.6%) at diagnosis. PPFE showed the most impaired lung function and the highest mortality (26.3%), during a median follow-up of 69.5 months, followed by PAP (6.2%) and BHD (1.8%). During follow-up, cancer was reported in 25.0% of patients with BHD. Treatment strategies varied by disease: corticosteroids were commonly used in HP (86.9%), PPFE (42.1%), and PLCH (32.5%); sirolimus in LAM (53.5%); pirfenidone in PPFE (42.1%); and whole-lung lavage in PAP (23.5%).

This is the first nationwide rare ILD registry in Korea, demonstrating heterogeneity in clinical features and outcomes and emphasizing the need for disease-specific diagnostic and therapeutic strategies.