ssels that can cause excessive bleeding. people with this condition can develop abnormal blood vessels called arteriovenous malformations (avms) in several areas of the body. if they are on the skin, they are called telangiectasias. the avms can also develop in other parts of the body, such as the brain, lungs, liver, or intestines. hht is caused by mutations in the acvrl1, eng, and smad4 genes. i