ACVRL1 and pulmonary arterial hypertension: In cases where BMPR2 mutations are not detected in familial PAH or IPAH patients under 40, or when PAH is identified in individuals with a personal or family history of hereditary hemorrhagic telangiectasia, screening for Activin A Receptor Like Type 1 (ACVRL1) and endoglin (ENG) genes may be recommended.