[Preclinical and prenatal diagnosis of familial adenomatous polyposis]

In order to investigate the possibility of preclinical and prenatal genetic diagnosis of familial adenomatous polyposis (FAP) by means of DNA-systems and other markers, blood samples were collected from 246 persons in 29 families, including 90 with the clinical diagnosis FAP and 73 clinically unaffected first degree relatives (persons at risk). The material was studied with up to 4 DNA-marker systems located in the region around the disease gene. Among the first degree relatives eight (11%) had probably inherited the disease gene, while 31 persons (42%) in this risk group had probably not inherited the gene. It was not possible to evaluate the risk in the remaining 34 persons (47%). In 45 (85%) out of 53 persons under 40 years the DNA-systems were informative, so that it would be possible to offer the option of prenatal diagnosis. It is concluded that preclinical and possibly prenatal genetic diagnosis may be offered; but the current practice of prophylactic proctosigmoidoscopic surveillance should be maintained.