Cystic fibrosis--a single locus disease? Results of a population genetics study.

In a population genetics study of cystic fibrosis (CF), we investigated the state of health of 1276 first cousins of CF index patients. Six hundred seventy-five married aunts and uncles (siblings of CF index patients' mothers and fathers) who had at least one child were interviewed. In only 1 of these 675 families, three children of a total of eight had died of CF. If CF occurs more frequently than in 1 in 3000 newborn babies in our population, our investigation supports the hypothesis that CF is caused by mutations at more than one locus. We also determined that the evidence furnished by such a study of other, more uncommon autosomal recessive disorders is limited.