ACVRL1 and hereditary hemorrhagic telangiectasia: As far as the genotype-phenotype correlation is concerned, most of the pulmonary arteriovenous malformations (PAVMs) in our study were detected in HHT patients with mutations for ENG. This phenomenon has already been described by previous studies given in literature, stating that mutations of ENG are mainly observed in HHT type 1 with an incidence of up to 40% for PAVMs, whereas mutations of ALK1 are primarily observed in HHT type 2 with an incidence of only 14% for PAVMs, which clinically distinguishes these two types of mutation [3,7,28,36].