[Mendelian arterial diseases. Pseudoxanthoma elasticum, Ehlers-Danlos vascular syndrome, Rendu-Osler disease].

Understanding the features of the various hereditary vascular pathologies allows consideration and confirmation of the diagnosis, and a search for treatable hidden disorders, avoiding harmful investigations, initiating follow up, performing family investigations and providing genetic counselling. Pseudoxanthoma elasticum must be considered in the presence of calcified distal arteriopathy of the lower limbs in a young subject without any other aetiological aspects. Cutaneous or mucosal lesions confirmed on histological examination, angioid streaks at the back of the eye and a family history support the diagnosis, which is confirmed by showing pathogenic mutations of the ABCC6 gene. It is then important to search for a peripheral disorder in other arterial territory, a low grade coronaropathy, hypertension and an endocardial disorder. Prescription of antithrombotics must be made carefully because of the risk of gastro-intestinal haemorrhage. Vascular Ehlers-Danlos syndrome is suspected in a subject less than 30 years old with diffuse aneurysmal disease, spontaneous arterial rupture or dissection, a carotido-cavernous fistula or early onset varices. Demonstrating an ecchymotic tendency or an acrogeric morphology, especially in a familial context, warrants cutaneous biopsy for anatomopathological examination and fibroblast culture for a study of the C0L3A1 gene. When the diagnosis is suggested, it is advisable to prohibit any arterial puncture, cold surgery or gastro-intestinal endoscopy. The search for aneurysmal lesions must be performed by non-invasive imaging. The therapeutic management requires specialised teams. The combination of repeated epistaxis, muco-cutaneous telangectasia and similar characteristics in a family suggests the diagnosis of Osler-Weber-Rendu disease. The search for iron deficiency, gastro-intestinal bleeds and pulmonary, hepatic or cerebral arterio-venous malformations is then necessary. Besides skilled endovascular management when indicated, it is important to advise every patient with a pulmonary arterio-venous malformation to take antibiotic prophylaxis against cerebral abscess in situations at risk of bacteraemia.