Bronchiectasis With Or Without Elevated Sweat Chloride 3

A number sign (#) is used with this entry because of evidence that bronchiectasis with or without elevated sweat chloride (BESC3) can be caused by mutation in the gene encoding the gamma subunit of the epithelial sodium channel (SCNN1G; 600761).

For discussion of genetic heterogeneity of bronchiectasis with or without elevated sweat chloride, see BESC1 (211400).

Molecular Genetics

Fajac et al. (2008) screened the SCNN1G gene in 55 patients with idiopathic bronchiectasis who had 1 or no mutations in the CFTR gene (602421) and identified heterozygosity for 2 missense mutations in 3 patients without mutation in CFTR, G183S (600761.0005) and E197K (600761.0006), respectively. All 3 patients had normal sweat chlorides; 1 had an abnormal nasal potential difference (NPD), whereas the other 2 had normal NPDs. The authors noted that the 2 patients with the E197K mutation were among the most severely affected of the patients without mutation in CFTR, with forced expiratory volumes in 1 second (FEV1s) that were 64% and 35% of predicted, respectively.

Mutesa et al. (2009) analyzed the CFTR gene in 60 unrelated Rwandan children who had CF-like symptoms and identified heterozygosity for a CFTR mutation in 5 patients (none were homozygous). Sequencing of the genes encoding the 3 subunits of the epithelial sodium channel (ENaC) revealed heterozygous mutations in SCNN1A (600228) and SCNN1B (600760) in 4 patients, respectively, whereas the remaining patient was heterozygous for a mutation in both SCNN1B and SCNN1G. Among the patients who were negative for mutation in CFTR, only known polymorphisms were found in the ENaC genes. Mutesa et al. (2009) concluded that some cases of CF-like syndrome in Africa may be associated with mutations in CFTR and ENaC genes.