Long-Term Prognosis and Transition Period until Progression in Fibrotic Hypersensitivity Pneumonitis

Area of Science:

• Pulmonology
• Interstitial Lung Diseases
• Fibrotic Lung Diseases

Background:

• Hypersensitivity pneumonitis (HP) is an interstitial lung disease with fibrotic (fHP) and nonfibrotic (nfHP) forms.
• Fibrosis in HP is linked to disease progression and poor prognosis, but the transition to progressive pulmonary fibrosis (PPF) and its predictors are not well understood.

Purpose of the Study:

• To investigate the incidence of progressive pulmonary fibrosis (PPF) in patients with fibrotic hypersensitivity pneumonitis (fHP).
• To identify predictors of PPF development and survival in fHP patients.
• To understand the clinical course and outcomes of fHP.

Main Methods:

• Retrospective review of adult HP patients diagnosed between 2010-2022.
• Classification of patients into fHP and nfHP groups, with follow-up of at least one year.
• Analysis of clinical, functional, radiological, and histological data, defining PPF per ATS/ERS/JRS/ALAT guidelines.

Main Results:

• Of 191 HP patients analyzed (153 fHP, 38 nfHP), 49.7% of fHP patients developed PPF after a median of 3.2 years.
• Median survival was shorter for fHP patients with PPF (4.8 years) compared to those without (6.3 years).
• Independent predictors for PPF and survival included lower forced vital capacity, elevated lactate dehydrogenase, fibroblastic foci, and microscopic honeycombing.

Conclusions:

• Approximately half of fHP patients progress to PPF within a few years, experiencing significantly reduced survival.
• Early identification of high-risk fHP patients is essential for initiating timely anti-fibrotic therapies.
• Improved outcomes may be achievable through prompt recognition and treatment of progressive fibrotic lung disease in HP.