Rare but serious: pulmonary vascular disease around the world.

Pulmonary arterial hypertension (PAH), a subtype of pulmonary hypertension (PH) classified under Group 1 of the World Health Organization (WHO) classification, is a progressive disorder characterized by pulmonary vascular remodeling, increased pulmonary vascular resistance, and eventual right heart failure. While common etiologies are well described, less frequent causes are often underrecognized, despite their potential impact on prognosis and therapeutic decision-making. During the April 2025 International Society of Heart and Lung Transplantation (ISHLT) annual meeting in Boston, USA, a dedicated symposium entitled "Rare but Serious: Pulmonary Vascular Disease Around the World" addressed these overlooked forms of pulmonary vascular disease (PVD). This review summarizes the latest diagnostic and therapeutic insights into several rare but clinically significant entities, including portopulmonary hypertension (PoPH), PH associated with hematologic disorders, HIV-associated PAH, high-altitude PH and PAH, and schistosomiasis-associated PAH (Sch-PAH). Raising awareness and understanding of these conditions is critical to ensuring timely diagnosis, personalized treatment, and improved patient outcomes.