Correlation of phenotypic and genetic heterogeneity in cystic fibrosis: Variability in sweat electrolyte levels contributes to heterogeneity and is increased with the XV-2c/KM19 B haplotype

Abstract

We have reinvestigated a classification of clinical heterogeneity among cystic fibrosis (CF) patients that we previously reported and investigated the possible relationship of the identified CF subgroups to haplotypes around the CF gene and to HLA-DR haplotypes. Age-corrected values for sweat electrolytes, rate of progression of lung disease as assessed by Brasfield chest x-ray scores, and severity of pancreatic insufficiency as assessed by daily supplemented enzyme dosage were obtained for 55, 59, and 59 patients, respectively. XV-2c and KM19 RFLPs were determined by hybridization to TaqI and PstI digests of human genomic DNA, respectively, and analysis of mutations by PCR amplification followed by allele-specific oligo-deoxy-nucleotide hybridization was performed for 29 patients. HLA-DR restriction fragment length polymorphisms (RFLPs) were determined by hybridization of cDNA Β1 and genomic DQΑ probes to TaqI digests of human genomic DNA. The results show that the previous subdivision on the basis of age-corrected levels of sweat electrolytes, as well as measures of severity of lung disease and pancreatic disease, is valid. In addition, the C and D haplotypes are associated with lower age-corrected sweat sodium level. No significant relationship between CF haplotypes and the other two disease variables or between HLA-DR haplotypes and any of the clinical variables was found.