ACVRL1 and hereditary hemorrhagic telangiectasia: Thus, Eng+/− and Alk1+/− animals with 129/Ola background develop highly penetrant and frequent clinical manifestations similar to those of HHT, such as dilated vessels, nosebleeds, telangiectases and vascular lesions in the liver, the nail bed, ears, intestine and skin (24, 51, 52).