Hereditary hemorrhagic telangiectasia (HHT) or the Rendu-Osler-Weber disease is a systemic fibrovascular autosomal dominant dysplasia, recognised when three of the following four clinical manifestations are present, according to the proposal of Shovlin .: recurrent nosebleeds, lelangiectasias of the skin, visceral lesions, and positive family history. HHT is often difficult to diagnose on the basis of history and physical examination alone, especially in infants and children. The signs and symptoms of HHT are nonspecific and are extremely variable within families. Given the frequent occurrence of clinically silent lesions in lung and brain arteriovenous malformations which can result in morbidity or death, much consideration should be given to screening patients with HHT for asymptomatic fistulae and to their treating once they are discovered. Presymptomatic interventions in such cases may substantially affect the outcome. It may be possible to state that lesions of HHT arise early in life, but do not reach sufficient size to cause symptoms until the second decade. Furthermore, as clinical manifestations often occur later in life, the development and the implementation of a molecular diagnosis will allow the identification of subjects with no evident signs of the disease but carrying the familial mutation. This is fundamental in order to establish reliable screening protocols for the prevention and cure of the disease and, to determine the presence of family members with no disease-associated mutation, who do not require further clinical screening.