Previous studies indicated only men with homozygous of two severe pathogenic CFTR mutations could develop the disease CF, men with CFTR compound heterozygote or a single pathogenic CFTR exon mutation, in some cases combined with a 5T splice variant, may only have iCBAVD phenotype without symptoms from the respiratory tract and gastrointestinal system (Yu et al., 2012). Here, CFTR is linked to cystic fibrosis.