2 STEP PROCEDURE FOR EARLY DIAGNOSIS OF POLYCYSTIC KIDNEY-DISEASE WITH POLYMORPHIC DNA MARKERS ON BOTH SIDES OF THE GENE

Polymorphic DNA markers can now be used for presymptomatic and prenatal diagnosis of the autosomal dominant form of polycystic kidney disease (PKD). A detailed map is known for the chromosomal region around the PKD1 gene on the short arm of chromosome 16. We present here a simple, two step procedure for diagnosis of PKD1 by family studies. Using this approach, at least 92% of random subjects are informative for polymorphic DNA markers bracketing the PKD1 gene. The recombination rate between these flanking markers is on average 10%. In non-recombinants (90% of family members), the accuracy of diagnosis using DNA markers is >99%. We conclude that sufficient well defined DNA markers are now available for routine diagnosis of PKD1. We recommend, however, that prenatal diagnosis of PKD by chorionic villi sampling should be attempted only after the linkage phase of the DNA markers has been established by haplotyping the index family. Since autosomal dominant PKD has been found to be genetically heterogeneous, families should be of sufficient size to rule out the rare form of PKD not caused by a mutation on the short arm of chromosome 16.