ACVRL1 and hereditary hemorrhagic telangiectasia: According to our results, ocular involvement in Spanish HHT patients is more frequent in people with mutations in the endoglin gene, which is responsible for HHT subtype 1 (HHT1), than in patients with mutations in the ACVRL1/ALK1 gene, responsible for HHT subtype 2 (HHT2).