Genetic epidemiology of hereditary hemorrhagic telangiectasia in a local community in the northern part of Japan.

Hereditary hemorrhagic telangiectasia (HHT or Rendu-Osler-Weber syndrome) is an autosomal dominant disorder characterized by aberrant vascular development. We report here a genetic epidemiologic study in a county, A, in the Akita prefecture (population 1.2 million) located in northern Japan. Nine HHT patients who had been referred to tertiary-care hospitals were located in and near the study county. A total of 137 pedigree members were traced of which 81 were alive and 32 were affected by HHT. Complications associated with cerebral or pulmonary arteriovenous malformations were proven in six out of seven families. Linkage analysis in two large families revealed a weak yet suggestive linkage to the HHT1 locus (encoding endoglin; ENG). Three novel mutations were found in four families, all of which led to a frameshift: a G to C transversion at the splicing donor site of intron 3 (Inv3+1 G>C) in one family, one base pair insertion (A) at nucleotide 828 (exon 7) of the endoglin cDNA in two large families (c.828-829 ins A), and a four base pair deletion (AAAG) beginning with nucleotide 1120 (exon 8) of the endoglin cDNA (c.1120-1123 delAAAG) in one family. The insertion of A in exon 11 (c.1470-1471 insA) mutation found in one family has also been reported in a European family. No endoglin gene mutations were found in two families. The population prevalence of HHT in the county was estimated to be 1:8,000 approximately 1:5,000, roughly comparable with those reported in European and U.S. populations, which is contradictory to the traditional view that HHT is rare among Asians. We recommend that families with HHT be screened for gene mutations in order that high-risk individuals receive early diagnosis and treatment initiation that will substantially alter their clinical course and prognosis.