**Study Overview:** This study is about observing patients with a type of lung disease called pulmonary hypertension associated with interstitial lung disease (PH-ILD). It's a registry, which means collecting information without giving any new treatment. **Pulmonary hypertension** means high blood pressure in the lungs' blood vessels. **Interstitial lung disease** affects the tissue and space around the air sacs of the lungs. Patients are divided into three groups: 1. Not using a medicine called inhaled treprostinil. 2. Recently started using Tyvaso (a medicine for PH-ILD). 3. Using Tyvaso for over 60 days. **Key Points:** - **Duration**: Participation can last up to 5 years. - **Visits**: Data collection occurs every 6 or 12 months with tests like lung function, blood tests, and questionnaires. - **Eligibility**: Must be 18 or older with specific lung conditions; cannot have certain other types of PH or be using some medications. The study aims to better understand how patients are treated and how well they do over time.