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PubMed This is a summary of 19 peer-reviewed journal articles Updated
Urology · Congenital Bilateral Absence of the Vas Deferens

Genetics and the Cystic Fibrosis Connection

At a Glance

In 80% to 97% of cases, Congenital Bilateral Absence of the Vas Deferens (CBAVD) is caused by a mutation in the CFTR gene. While related to Cystic Fibrosis, CBAVD typically involves mild mutations that primarily affect male fertility. Genetic testing is crucial for safe family planning.

When a man is diagnosed with CBAVD, the question is often “why?” The answer lies in your DNA. In the vast majority of cases—approximately 80% to 97%—the cause is a mutation in the CFTR gene [1][2].

The CFTR Connection

The CFTR gene (Cystic Fibrosis Transmembrane Conductance Regulator) provides instructions for a protein that acts like a “gate” on the surface of cells. This gate controls the movement of salt and water in and out of the cells that produce mucus, sweat, and digestive juices [3].

In the womb, the developing reproductive tract is very sensitive to these salt levels. If the CFTR “gates” aren’t working perfectly, the fluid inside the developing tubes (the Wolffian ducts) becomes too thick or the salt balance is off. This causes the tubes to either fail to form correctly or to waste away (involute) before birth [4][5].

Is CBAVD the same as Cystic Fibrosis?

CBAVD is considered a CFTR-related disorder, but it is distinct from classic Cystic Fibrosis (CF) [6][1].

  • Classic CF: Usually caused by two “severe” mutations. This leads to heavy, thick mucus in the lungs and pancreas, causing serious breathing and digestive problems [7][8].
  • CBAVD: Usually involves at least one “mild” mutation (like the 5T allele) [9]. These mutations allow just enough CFTR protein to work so that the lungs and pancreas stay healthy, but not enough to allow the delicate vas deferens to develop [1][10].

While the missing vas deferens is often the only symptom you will ever experience [6], some men with CBAVD may later notice very mild CF-related issues, such as chronic sinusitis or a persistent, mild cough [8]. Depending on the specific mutations found, your care team may suggest occasional follow-ups with a primary care doctor or pulmonologist just to ensure your lungs and sinuses remain healthy over time.

Other Genetic Causes

While CFTR is the most common cause, scientists have discovered that other genes can also prevent the vas deferens from forming. These are often suspected when CFTR testing comes back normal.

ADGRG2 (The X-Linked Connection)

If you do not have a CFTR mutation, the next most likely culprit is a gene called ADGRG2 [11][12].

  • This gene is located on the X chromosome [12].
  • Like CFTR, it helps regulate the fluid environment in the male reproductive tract [13].
  • Because it is X-linked, it can be passed from a mother (who is a carrier and has no symptoms) to her son [12].

Other Rare Genes

Emerging research has also linked the SLC9A3 gene to CBAVD [14]. This gene works closely with CFTR to maintain the “microenvironment” needed for the tubes to survive during development [15].

Why Genetics Matter for You

Knowing your specific genetic blueprint is crucial for two reasons:

  1. Risk to Offspring: If you carry a CFTR mutation and your partner is also a carrier, there is a risk that your child could have classic Cystic Fibrosis [16][17].
  2. Reproductive Planning: Understanding the genetic cause helps your care team determine the best way to retrieve sperm and whether Preimplantation Genetic Testing (PGT) is needed to screen embryos before pregnancy [18][19].

Common questions in this guide

Is CBAVD the same thing as Cystic Fibrosis?
CBAVD is a CFTR-related disorder, but it is not classic Cystic Fibrosis. While classic CF causes severe lung and digestive issues, CBAVD usually involves milder genetic mutations where the missing vas deferens is the only symptom.
Why do I need genetic testing if I only have male infertility?
Testing for the CFTR gene is crucial because if both you and your partner are carriers of mutations, there is a significant risk of passing classic Cystic Fibrosis to your child. Knowing your genetics helps your doctor plan the safest path for building your family.
What happens if my CFTR genetic testing comes back negative?
If CFTR testing is normal, your doctor may look for other rare genetic causes. The most common alternative is a mutation in the ADGRG2 gene, which is passed down on the X chromosome and can prevent the vas deferens from forming during fetal development.
Will I develop lung or breathing problems if I have CBAVD?
Most men with CBAVD only experience infertility, but some may develop very mild symptoms like chronic sinusitis or a persistent cough later in life. Your care team may suggest occasional follow-ups with a primary care doctor or pulmonologist to monitor your long-term respiratory health.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Was my genetic testing a 'standard carrier screen' or a 'full gene sequencing' for CFTR?
  2. 2.Did the test look specifically for the 5T allele or other 'mild' mutations?
  3. 3.If my CFTR testing is negative, should we test for the ADGRG2 gene on the X chromosome?
  4. 4.Based on my genetics, what is the specific risk that our child could have classic Cystic Fibrosis versus CBAVD?
  5. 5.Does my specific mutation have any implications for my long-term lung or sinus health?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (19)
  1. 1

    Prevalence of CBAVD in azoospermic men carrying pathogenic CFTR mutations - Evaluated in a cohort of 639 non-vasectomized azoospermic men.

    Fedder J, Jørgensen MW, Engvad B

    Andrology 2021; (9(2)):588-598 doi:10.1111/andr.12925.

    PMID: 33095972
  2. 2

    Compound heterozygous mutations in CFTR causing congenital bilateral absence of the vas deferens in a Chinese pedigree.

    Li L, Qu X, Cui C, et al.

    Molecular genetics & genomic medicine 2024; (12(1)):e2364 doi:10.1002/mgg3.2364.

    PMID: 38284450
  3. 3

    High-resolution imaging of the actin cytoskeleton and epithelial sodium channel, CFTR, and aquaporin-9 localization in the vas deferens.

    Sharma S, Kumaran GK, Hanukoglu I

    Molecular reproduction and development 2020; (87(2)):305-319 doi:10.1002/mrd.23317.

    PMID: 31950584
  4. 4

    Non-obstructive vas deferens and epididymis loss in cystic fibrosis rats.

    Plyler ZE, Birket SE, Schultz BD, et al.

    Mechanisms of development 2019; (155()):15-26 doi:10.1016/j.mod.2018.10.002.

    PMID: 30391480
  5. 5

    Prenatal initiation of elexacaftor/tezacaftor/ivacaftor via carrier mother prevents congenital bilateral absence of vas deferens in a male infant with cystic fibrosis.

    Thee S, Aleksander P, Lechner L, et al.

    Journal of cystic fibrosis : official journal of the European Cystic Fibrosis Society 2026; doi:10.1016/j.jcf.2026.02.001.

    PMID: 41654435
  6. 6

    Molecular Genetics of Cystic Fibrosis Transmembrane Conductance Regulator: Genotype and Phenotype.

    Sosnay PR, Raraigh KS, Gibson RL

    Pediatric clinics of North America 2016; (63(4)):585-98.

    PMID: 27469177
  7. 7

    Precision medicine advances in cystic fibrosis: Exploring genetic pathways for targeted therapies.

    R S A, R M, Sastri KT, et al.

    Life sciences 2024; (358()):123186 doi:10.1016/j.lfs.2024.123186.

    PMID: 39471902
  8. 8

    Positional effects of premature termination codons on the biochemical and biophysical properties of CFTR.

    Yeh JT, Hwang TC

    The Journal of physiology 2020; (598(3)):517-541 doi:10.1113/JP278418.

    PMID: 31585024
  9. 9

    Genetic analysis and intracytoplasmic sperm injection outcomes of Chinese patients with congenital bilateral absence of vas deferens.

    Cheng H, Yang S, Meng Q, et al.

    Journal of assisted reproduction and genetics 2022; (39(3)):719-728 doi:10.1007/s10815-022-02417-z.

    PMID: 35119551
  10. 10

    Sperm retrieval and intracytoplasmic sperm injection outcomes in men with cystic fibrosis disease versus congenital bilateral absence of the vas deferens.

    McBride JA, Kohn TP, Mazur DJ, et al.

    Asian journal of andrology 2021; (23(2)):140-145 doi:10.4103/aja.aja_48_20.

    PMID: 32930103
  11. 11

    Novel ADGRG2 truncating variants in patients with X-linked congenital absence of vas deferens.

    Pagin A, Bergougnoux A, Girodon E, et al.

    Andrology 2020; (8(3)):618-624 doi:10.1111/andr.12744.

    PMID: 31845523
  12. 12

    Truncating Mutations in the Adhesion G Protein-Coupled Receptor G2 Gene ADGRG2 Cause an X-Linked Congenital Bilateral Absence of Vas Deferens.

    Patat O, Pagin A, Siegfried A, et al.

    American journal of human genetics 2016; (99(2)):437-42.

    PMID: 27476656
  13. 13

    Commentary on: A novel hemizygous loss-of-function mutation in ADGRG2 causes male infertility with congenital bilateral absence of the vas deferens.

    Oates RD

    Journal of assisted reproduction and genetics 2020; (37(6)):1327-1328 doi:10.1007/s10815-020-01834-2.

    PMID: 32451811
  14. 14

    SLC9A3 Affects Vas Deferens Development and Associates with Taiwanese Congenital Bilateral Absence of the Vas Deferens.

    Wu YN, Chen KC, Wu CC, et al.

    BioMed research international 2019; (2019()):3562719 doi:10.1155/2019/3562719.

    PMID: 30956978
  15. 15

    Loss of SLC9A3 decreases CFTR protein and causes obstructed azoospermia in mice.

    Wang YY, Lin YH, Wu YN, et al.

    PLoS genetics 2017; (13(4)):e1006715 doi:10.1371/journal.pgen.1006715.

    PMID: 28384194
  16. 16

    Congenital Bilateral Absence of the Vas Deferens.

    Cai Z, Li H

    Frontiers in genetics 2022; (13()):775123 doi:10.3389/fgene.2022.775123.

    PMID: 35222530
  17. 17

    Mutations of the cystic fibrosis transmembrane conductance regulator gene in males with congenital bilateral absence of the vas deferens: Reproductive implications and genetic counseling (Review).

    Cui X, Wu X, Li Q, Jing X

    Molecular medicine reports 2020; (22(5)):3587-3596 doi:10.3892/mmr.2020.11456.

    PMID: 33000223
  18. 18

    Genetics of CFTR and male infertility.

    Bieniek JM, Lapin CD, Jarvi KA

    Translational andrology and urology 2021; (10(3)):1391-1400 doi:10.21037/tau.2020.04.05.

    PMID: 33850775
  19. 19

    Congenital bilateral absence of the vas deferens as an atypical form of cystic fibrosis: reproductive implications and genetic counseling.

    de Souza DAS, Faucz FR, Pereira-Ferrari L, et al.

    Andrology 2018; (6(1)):127-135 doi:10.1111/andr.12450.

    PMID: 29216686

This page explains the genetic causes of CBAVD for educational purposes only. Always consult a genetic counselor or fertility specialist to accurately interpret your specific genetic test results and understand your reproductive options.

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