Intermediate-range sweat chloride concentration and Pseudomonas bronchitis. A cystic fibrosis variant with preservation of exocrine pancreatic function

Abstract

The clinical and laboratory characteristics of 7 patients with sweat chloride concentrations consistently between 40 and 60 meq/l were studied. Each had chronic Pseudomonas bronchitis and all lacked digestive symptoms. Laboratory findings indicated the preservation of exocrine pancreatic function. The patients included 2 of 5 children in 1 family and 2 of 4 in another. In a 3rd family, 1 of 5 siblings had an intermediate sweat chloride concentration, but another has a typical fibrosis value (105 meq/l). One patient died of respiratory failure; results of an autopsy showed bronchiolectasis typical of cystic fibrosis, but minimal pancreatic changes. A genetic basis for this variant of cystic fibrosis is suggested. These patients may be homozygous for a portion of a closely linked multigene cystic fibrosis locus or may have modifier genes that ameliorate the pancreatic and sweat lesions.