[Hereditary hemorragic telangiectasia: the state of art]

Abstract

Hereditary Hemorrhagic Telangiectasia (HHT) or Rendu-Osler-Weber syndrome, is a multisystemic vascular dysplasia. The disease is transmitted as a dominant autosomic character. The Hereditary Hemorrhagic Telangiectasia is differentiated in two subclasses: (1) HHT1, which is caused by mutation of ENG gene. This gene is localized on long arm of chromosome 9: (2) HHT2, which is caused by mutation of ALK-1 gene. This gene is located on long arm of chromosome 12. These two genes codify for two receptorial proteins: the endoglin and the activin-like protein 1; these proteins belong to receptorial superfamily of TGF-beta, which is involved in vascular remodelling and angiogenesis. Clinically, the consequences of these mutations are represented by the formation of cutaneous and/or mucous telangiectases and artero-venous fistulas. In both cases histological alteration is the same: extremely ectatic venules with numerous layers of myocytes around them. Arterioles communicate with venules directly without a capillary filter. Essentially, telangiectases manifest themselves with hemorrhages, while more common consequences of fistulas are secondary to formation of shunts with a possible thromboembolism; that is particularly serious in case of pulmonary artero-venous malformations. In 2000. Shovlin published 4 diagnostic criteria (criteria of Curaçao): (1) spontaneous and recurrent epistaxis; (2) multiple telangiectases; (3) visceral artero-venous malformations; (4) familiarity for HHT. Actually there is no possibility for a genetic therapy of HHT. Therefore, the therapeutic efforts are turned to control of symptoms and to the prevention of complications.