[Results of molecular diagnosis in 30 Austrian families with familial adenomatous polyposis].

Familial adenomatous polyposis is a dominantly inherited precancerous condition of the colorectum. The isolation of the responsible gene has facilitated the search for mutation in affected individuals and risk estimation for family members. The aim of our study was the assessment of the disease by molecular biological methods in order to estimate the risk for family members. Blood probes from 30 non-related Austrian families (44 persons affected, 61 at risk) were examined for detection of a defect in the adenomatous polyposis gene by means of the protein truncation test and, if necessary, by linkage analysis. The protein truncation test led to successful identification of the defect gene in 66.7% (20/30 families). In 3 families, the presymptomatic difference between mutation carriers and healthy subjects could only be assessed by linkage analysis. Genetic diagnosis enabled us to detect the disease before the onset of clinical symptoms in 16 persons at risk, 37 could be identified as genetically healthy. In 8 persons at risk out of 5/30 families we were unable to identify a defect gene by the methods used until now. In conclusion, we have succeeded in establishing genetic diagnosis of familial adenomatous polyposis using the protein truncation test in Austria. Our method of genetic risk estimation is an important step in Austria towards earlier diagnosis and well-timed therapy management, and helps to exclude persons at risk who are genetically healthy from the laborious screening program.