A rare frameshift variant in trans with the IVS9-5T allele of CFTR in a Chinese pedigree with congenital aplasia of vas deferens.

Congenital aplasia of vas deferens (CAVD) is an atypical form of cystic fibrosis (CF) and causes obstructive azoospermia and male infertility. Compound heterozygous variants of CFTR are the main cause of CAVD. However, most evidence comes from genetic screening of sporadic cases and little is from pedigree analysis. In this study, we performed analysis in a Chinese pedigree with two CAVD patients in order to determine the genetic cause of this familial disorder. In the present study, we performed whole-exome sequencing and co-segregation analysis in a Chinese pedigree involving two patients diagnosed with CAVD. We identified a rare frameshift variant (NM_000492.3: c.50dupT;p.S18Qfs*27) and a frequent CBAVD-causing variant (IVS9-TG13-5T) in both patients. The frameshift variant introduced a premature termination codon and was not found in any public databases or reported in the literature. Co-segregation analysis confirmed these two variants were in compound heterozygous state. The other male members, who harbored the frameshift variant and benign IVS9-7T allele, did not have any typical clinical manifestations of CF or CAVD. Our findings may broaden the mutation spectrum of CFTR in CAVD patients and provide more familial evidence that the combination of a mild variant and a severe variant in trans of CFTR can cause vas deferens malformation.