Pulmonary Hypertension Complicating Interstitial and Granulomatous Lung Diseases

Pulmonary hypertension (PH) carries a poor prognosis in interstitial lung diseases (ILDs). Its prevalence depends on the underlying condition, the most common being idiopathic pulmonary fibrosis, connective tissue disease-related ILD, sarcoidosis, and pulmonary Langerhans cell histiocytosis (PLCH). Although hypoxic vasoconstriction and loss of pulmonary capillaries are important in the pathogenesis of ILD-associated PH, other mechanisms may play a role, including the release of diverse cytokines and growth factors during fibrogenesis which induce vascular remodeling. This intrinsic vasculopathy may prevail in the venous side in sarcoidosis and PLCH. As a result, a small proportion of ILD patients may exhibit ‘out of proportion’ PH, i.e. more severe than expected from functional impairment (mean pulmonary artery pressure > 35–40 mm Hg). The accuracy of echocardiography for the detection of PH is weak in ILDs. Management of ILD-associated PH mainly relies on supplemental oxygen and lung transplantation in otherwise eligible patients. Treatments targeted to the underlying ILD do not usually affect the course of PH, with the exception of rare cases of nonfibrotic sarcoidosis responding to corticosteroids. Data on the efficacy and safety of pulmonary arterial hypertension-specific agents are lacking. Further controlled trials are warranted and should integrate the concept of disproportionate PH in their design.