Multicenter Surveillance of Cystic Fibrosis in Korean Children

Abstract

Purpose: Cystic fibrosis (CF), caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, is rare among non-Caucasians. We aimed to identify the clinical features and CFTR mutations in Korean children.

Methods: We included 18 pediatric patients with CF diagnosed using sweat chloride test or genetic analysis for 30 years. HEK293 cells were transfected with wild-type CFTR, ΔF508-CFTR, and L441P-CFTR mutant plasmids for 24 hours and treated with CFTR correctors (VX809 and VX661).

Results: The median age at diagnosis was 9.2 years. Eleven patients had growth retardation, and 6 had a respiratory failure at diagnosis. Genetic analysis was used for all patients, while sweat testing was for 8 patients. At diagnosis, the median z scores of forced expiratory volume in one second (FEV1), FEV1/forced vital capacity, and forced expiratory flow at 25%-75% of forced vital capacity were -3.61 (-5.78, 1.78), -3.38 (-4.40, -0.60), and -4.45 (-5.78, 0.54), respectively. Two patients were treated with dornase alfa and only one with CFTR modulator. Patients were followed up for 3.7 years as a median. Four patients died at 10.6 years, with 4.2 years of post-diagnosis survival. The most common mutation was exon 16-17b deletion (19.4%). Among 11 single nucleotide variants, c.1322T>C (p.Leu441Pro, L441P) was detected in 4 patients. In the functional assay, L441P-CFTR correction was well restored by CFTR correctors compared with ΔF508.

Conclusions: CF is extremely rare in Korean children and is caused by different mutations from those commonly observed in Caucasians. Early diagnosis and treatment availability may improve outcomes. CFTR modulators may be effective for Asian patients with rare CFTR mutations, c.1322T>C (p.Leu441Pro).

Keywords: Cystic fibrosis; Korea; child; cystic fibrosis transmembrane conductance regulator; mutation.

Figure. Rescue of L441P using VX809. Aldolase A was blotted as a loading control. Most wild-type CFTR proteins were detected in the fully glycosylated mature form (band C), whereas virtually all L441P mutant proteins appeared in the core-glycosylated form of around 150 kDa (band B). When treated with VX809, L441P showed better restoration of the folding defect than ΔF508.

CFTR, cystic fibrosis transmembrane conductance regulator.