What are the genetic changes related to hereditary hemorrhagic telangiectasia ?
Mutations in the ACVRL1, ENG, and SMAD4 genes cause hereditary hemorrhagic telangiectasia.  Hereditary hemorrhagic telangiectasia type 1 is caused by mutations in the gene ENG. Type 2 is caused by mutations in the gene ACVRL1. Juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome is caused by mutations in the gene SMAD4. All these genes provide instructions for making proteins that are found in the lining of the blood vessels. These proteins interact with growth factors that control blood vessel development. The gene involved in hereditary hemorrhagic telangiectasia type 3 is not known, but is believed to be located on chromosome 5.  Mutations in these genes generally prevent the production of the associated protein, or result in the production of a defective protein that cannot fulfill its function. An individual with a mutated gene will therefore have a reduced amount of the functional protein available in the tissue lining the blood vessels. This deficiency is believed to result in the signs and symptoms of hereditary hemorrhagic telangiectasia.