Purpose: Hereditary hemorrhagic telangiectasia is an autosomal dominant disorder characterized by arteriovenous malformations (AVM), mostly cutaneous and mucous (telangiectases), but also involving the lungs (PAVM), liver (HAVM) and brain (CAVM). We studied the relationship between the phenotype and genotype in patients with a proven mutation in either ENG (HHT1) or ACVRL1 (HHT2). Methods: Clinical features and their age of onset were compared between HHT1 and HHT2. The type of mutation was also analyzed. Clinical manifestations were distinguished from lesions found by screening. Results: Ninety-three HHT1 patients and 250 HHT2 patients were included. Epistaxis occurred later in HHT2, with incomplete penetrance (P Ͻ 0.0001). Symptomatic PAVMs were more frequent in HHT1 (34.4 vs. 5.2%, P Ͻ 0.001), as were cerebral abscesses (7.5 vs. 0.8%, P ϭ 0.002).Gastrointestinal bleeding occurred more frequently in HHT2 (16.4 vs. 6.5%, P ϭ 0.017). Symptomatic hepatic involvement was only seen in HHT2 patients. PAVMs were more frequently detected in asymptomatic HHT1 patients (54 vs. 12.8%, P Ͻ 0.0001). PAVMs and HAVMs were often family clustered in HHT1 and HHT2, respectively. Truncating mutations were associated with a higher frequency of epistaxis and telangiectasis, in HHT2. Conclusion: This study shows major differences between HHT1 and HHT2 phenotypes, which should be taken into account for future clinical studies. Genet Med 2007:9(1):14-22.

Juvenile polyposis (JP) and hereditary hemorrhagic telangiectasia (HHT) are clinically distinct diseases caused by mutations in SMAD4 and BMPR1A (for JP) and endoglin and ALK1 (for HHT). Recently, a combined syndrome of JP-HHT was described that is also caused by mutations in SMAD4. Although both JP and JP-HHT are caused by SMAD4 mutations, a possible genotype:phenotype correlation was noted as all of the SMAD4 mutations in the JP-HHT patients were clustered in the COOH-terminal MH2 domain of the protein. If valid, this correlation would provide a molecular explanation for the phenotypic differences, as well as a pre-symptomatic diagnostic test to distinguish patients at risk for the overlapping but different clinical features of the disorders. In this study, we collected 19 new JP-HHT patients from which we identified 15 additional SMAD4 mutations. We also reviewed the literature for other reports of JP patients with HHT symptoms with confirmed SMAD4 mutations. Our combined results show that although the SMAD4 mutations in JP-HHT patients do show a tendency to cluster in the MH2 domain, mutations in other parts of the gene also cause the combined syndrome. Thus, any mutation in SMAD4 can cause JP-HHT. Any JP patient with a SMAD4 mutation is, therefore, at risk for the visceral manifestations of HHT and any HHT patient with SMAD4 mutation is at risk for early onset gastrointestinal cancer. In conclusion, a patient who tests positive for any SMAD4 mutation must be considered at risk for the combined syndrome of JP-HHT and monitored accordingly.

BackgroundHereditary hemorrhagic telangiectasia is a genetic disease characterized by teleangiectasias involving virtually every organ. There are limited data in the literature regarding the natural history of liver vascular malformations in hemorrhagic telangiectasia and their associated morbidity and mortality.AimThis prospective cohort study sought to assess the outcome of liver involvement in hereditary hemorrhagic telangiectasia patients.MethodsWe analyzed 16 years of surveillance data from a tertiary hereditary hemorrhagic telangiectasia referral center in Italy. We considered for inclusion in this study 502 consecutive Italian patients at risk of hereditary hemorrhagic telangiectasia who presented at the hereditary hemorrhagic telangiectasia referral center and underwent a multidisciplinary screening protocol for the diagnosis of hereditary hemorrhagic telangiectasia. Of the 502 individuals assessed in the center, 154 had hepatic vascular malformations and were the subject of the study; 198 patients with hereditary hemorrhagic telangiectasia and without hepatic vascular malformations were the controls. Additionally, we report the response to treatment of patients with complicated hepatic vascular malformations.ResultsThe 154 patients were included and followed for a median period of 44 months (range 12–181); of these, eight (5.2%) died from VM-related complications and 39 (25.3%) experienced complications. The average incidence rates of death and complications were 1.1 and 3.6 per 100 person-years, respectively. The median overall survival and event-free survival after diagnosis were 175 and 90 months, respectively. The rate of complete response to therapy was 63%.ConclusionsThis study shows that substantial morbidity and mortality are associated with liver vascular malformations in hereditary hemorrhagic telangiectasia patients.

On the basis of our proposed grading, hepatic VMs can be easily classified in subjects with HHT by Doppler US. Depending on the degree of hepatic vascular derangement, appropriate programs for follow up and/or therapy can be designed.