Understanding Delays in the Diagnosis of Pulmonary Arterial Hypertension and Rare Diseases in Brazil: A Multicenter Observational Study \--- Pulmonary arterial hypertension (PAH) is a rare, progressive, and life-threatening disease that affects the arteries of the lungs and the right side of the heart. Early diagnosis is essential to initiate appropriate treatment and improve patient outcomes. However, worldwide studies show that there is often a significant delay between the onset of symptoms and the final diagnosis. This delay may lead to disease progression and worse survival. This multicenter observational study aims to understand the time from the first symptoms to the diagnosis of PAH and other rare diseases across several Brazilian reference centers. By analyzing medical records and patient journeys, the investigators intends to identify factors contributing to delayed diagnosis and potential opportunities for earlier detection. The study includes adult patients diagnosed with PAH or other selected rare diseases within the last five years. The investigators will analyze time to diagnosis, number and type of physicians consulted, tests performed, and possible misdiagnoses. Our goal is to support the development of strategies that reduce diagnostic delay and improve access to specialized care for people living with rare diseases. This study does not involve any intervention and poses no additional risk to participants, as it is based solely on retrospective data from medical records.