Cystic fibrosis transmembrane conductance regulator channel dysfunction in non-cystic fibrosis bronchiectasis.
BACKGROUND
Although in patients with diffuse bronchiectasis (DB) and a normal sweat test the presence of one mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene is frequently observed, its pathogenic role in the development of DB remains unclear.


OBJECTIVE
To evaluate the association between CFTR heterozygosity and CFTR protein dysfunction in the airways of patients with DB.


METHODS
Nasal potential difference was measured in 122 patients with DB of unknown origin and with a normal sweat test (Cl(-) < 60 mmol/L). They were classified according to the presence of CFTR mutations: zero (85 patients), one (22 patients), or two mutations (15 patients). Control groups comprised 26 healthy subjects, 38 obligate heterozygotes for CFTR, and 92 patients with classic cystic fibrosis (CF) with an abnormal sweat test (Cl(-) > or = 60 mmol/L). Patients classified as mild-CF were carrying at least one mild mutation and patients classified as severe-CF were homozygous for the F508del mutation.


RESULTS
There was a continuum of airway CFTR dysfunction in the study population as shown by nasal potential difference measurements, ranging from normal values in healthy subjects, to intermediate values in subjects with DB, to highly abnormal values in subjects classified as severe-CF. This continuum of airway CFTR dysfunction was thus strongly associated with defects in the CFTR gene. Moreover, among patients with DB, a similar continuum in intermediate nasal potential difference was identified that was associated with the bearing of zero, one, or two CFTR mutations. These electrophysiological phenotypes and CFTR genotypes were also associated with the clinical phenotype, as shown by the frequency of Staphylococcus aureus and Pseudomonas aeruginosa bronchial colonization.


CONCLUSIONS
Our study supports the hypothesis that a unique CFTR mutation may have pathogenic consequences in patients with DB.
Bienvenu
Thierry
T
Service d'Explorations Fonctionnelles, Hôpital Cochin, 27 rue du Faubourg St-Jacques, Paris, France.
Sermet-Gaudelus
Isabelle
I
Burgel
Pierre-Regis
PR
Hubert
Dominique
D
Crestani
Bruno
B
Bassinet
Laurence
L
Dusser
Daniel
D
Fajac
Isabelle
I
D000328:Adult; D000368:Aged; D001987:Bronchiectasis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008875:Middle Aged; D009154:Mutation; D009297:Nasal Mucosa / Q000382:microbiology / Q000503:physiopathology; D010641:Phenotype; D011552:Pseudomonas Infections / Q000235:genetics / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification; D013203:Staphylococcal Infections / Q000235:genetics / Q000378:metabolism; D013211:Staphylococcus aureus / Q000302:isolation & purification; D013542:Sweat / Q000737:chemistry; D055815:Young Adult
C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator