Hereditary hemorrhagic telangiectasia and pulmonary arteriovenous malformations: Genetics, pathogenesis, diagnosis and clinical management

Hereditary haemorrhagic telangiectasia (HHT) is a syndrome with an autosomal dominant pattern of inheritance, characterised by abnormal direct artery-to-vein communications. These abnormal vascular communications range from small telangiectasia (in skin and mucous membranes) to large arteriovenous malformations (AVMs) in predominantly the brain, liver and lungs. These AVMs cause shunting and carry the risk for paradoxical embolism and haemorrhage and are therefore associated with significant morbidity and potential life threatening complications. Screening for AVMs can increase the life expectancy and therefore a multidisciplinary approach in a specialised HHT centre is necessary for optimal patient care. Pulmonary arteriovenous malformations (PAVMs) are associated with an increased risk of severe neurologic complications. Since most patients remain asymptomatic before these complications occur, screening and follow-up is recommended in all HHT patients. Transthoracic contrast echocardiography (TTCE) is the cornerstone in the screening for PAVMs, but in patients with significant shunting on TTCE, chest computed tomography (CT) is required to evaluate PAVM anatomy and identify PAVMs feasible for transcatheter embolisation. Depending on the existence and size of PAVMs at screening, different strategies for follow-up exist using mostly TTCE or chest CT.