Conclusion: The finding of several new unique mutations suggests that the genes causing hereditary hemorrhagic telangiectasia (HHT), i.e. endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1), have a relatively high mutation rate. As no single founder mutation was found, analysis of the whole coding sequences of ENG and ACVRL1 genes remains the first choice in genetic testing of new index patients with HHT.
Objectives: Our aim was to characterize specific mutations causing HHT in our hospital in Helsinki serving a population of 1 million inhabitants.
Patients and methods: HHT patients were searched from our hospital discharge records and their diagnoses were verified by review of patient records and interviews. Eight index patients who fulfilled HHT phenotypic criteria were tested. ENG and ACVRL1 mutations were identified by DNA sequencing of ENG and ACVRL1 coding regions.
Results: Of the eight index patients, four had a mutation in the ENG gene, three in the ACVRL1 gene, and one had no mutations. All the mutations were different and all the four ENG mutations and one of the ACVRL1 mutations were new and had not been described previously in other populations. All the affected first-degree relatives had the same mutation as the index case.