Navigating the Complexity of PH-ILD: From Molecular Mechanisms to Integrated Clinical Evaluation

Pulmonary Hypertension (PH) in patients with Interstitial Lung Disease (ILD) is a critical, yet underrecognized, complication that affects patients' quality of life and increases mortality. Emerging evidence further suggests that PH-ILD is not merely a consequence of hypoxia and parenchymal fibrosis, as the severity of pulmonary vascular disease often correlates poorly with the extent of fibrotic lung involvement, indicating more complex underlying pathophysiological mechanisms. Diagnosis requires a high index of suspicion when symptoms appear "disproportionate" to the degree of parenchymal lung disease. Key indicators include diffusing capacity for carbon monoxide (DLCO) < 45%, a forced vital capacity to diffusing capacity for carbon monoxide ratio (FVC/DLCO) > 1.6, and radiological findings of increased pulmonary artery diameter. While echocardiography and circulating biomarkers serve as useful screening tools, right heart catheterization remains the gold standard for definitive diagnosis. Early identification is essential for risk stratification, lung transplant evaluation, and determining eligibility for targeted pharmacological interventions, as this group of patients remains one of the most therapeutically challenging forms of pulmonary vascular disease. Ongoing research and advances in diagnostic tools are increasingly focused on refining phenotypic classification, identifying valuable biomarkers, and elucidating molecular drivers that may enable personalized treatment strategies in this heterogeneous patient group.