Linkage heterogeneity of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease has been shown to be closely linked to the alpha-hemoglobin complex on the short arm of chromosome 16. We describe a five-generation kindred, descendants of Sicilian immigrants, in which the disease occurs but without linkage to the alpha-hemoglobin complex. DNA probes were used in genetic-linkage studies on blood samples from 163 family members, of whom 71 were affected by or at risk for autosomal dominant polycystic kidney disease. Diagnoses were confirmed by ultrasound examination. In this family the frequency of recombination between the alpha-hemoglobin complex and the region previously shown to contain the mutation causing polycystic kidney disease exceeded 24 percent, indicating a mutation at a different locus. The clinical findings in this family were indistinguishable from those in other families with polycystic kidney disease. We conclude that there is a second gene for autosomal dominant polycystic kidney disease. This apparent heterogeneity means that prenatal and presymptomatic diagnosis must be approached with caution until a method is found to distinguish between the two forms of the disease.