Clinical hallmarks and genetic polymorphisms in the CFTR gene contribute to the disclosure of the A1006E mutation

Since the identification of the Cystic Fibrosis transmembrane conductance regulator (CFTR) gene in 1989, many genetic mutations have been found in cystic fibrosis (CF) patients. Dysfunctions of the CFTR gene are responsible for the highly variable clinical presentation ranging from severe CF, disseminated bronchiectasis, idiopathic chronic pancreatitis and congenital bilateral absence of vas deferens (CBAVD). Linkage disequilibrium studies have shown that some mutations are stringently coupled with polymorphisms in a genetic complex called haplotype. From a familial study of a patient with CBAVD, carrier of the A1006E mutation, we have observed its strict association with the polymorphism 5T-TG11. In order to speed up the genetic diagnosis and to correlate the clinical setting to this genetic feature, we have directly investigated the exon 17a, where the A1006E mutation is located, of five cystic fibrosis patients belonging to two unrelated families. All patients had the 5T-TG11 tract, F508del and one unknown mutation. One more family with two affected individuals carrying the Q220X/A1006E mutations was investigated for the poly-T polymorphism. All the members were found to have the A1006E mutation and the 5T-TG11 in the same DNA strand, demonstrating that this strategy is a reliable and inexpensive method for genotyping the CFTR gene. A detailed description of the clinical presentation and follow-up are provided in order to highlight common phenotypic features useful to improve the management of cystic fibrosis patients.