What is DFNB1?
DFNB1 is an inherited condition characterized by mild to profound hearing loss that is typically present from birth. In most cases, a person must have two variants in the GJB2 gene in order to have this condition. People with just one variant in the GJB2 gene are called carriers. They’re not expected to have DFNB1 themselves, but they could pass their variant on to their future children.
The genetics behind DFNB1
DFNB1 is most often caused by variants (differences) in the GJB2 gene. The GJB2 gene contains instructions for making a protein called gap junction beta 2, also known as connexin 26. This protein helps transport potassium ions and other molecules between cells. Proper movement of potassium ions in the inner ear is needed for the brain to process sound. Certain variants in the GJB2 gene impair the function of this protein.
What are the symptoms of DFNB1?
The only symptom of DFNB1 is mild to profound hearing loss, which is typically present from birth. Unlike some other forms of hearing loss, DFNB1 does not impact balance or movement.
Did you know?
DFNB1 affects people of all ethnicities. It is one of the most common causes of genetic hearing loss not accompanied by other symptoms.
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The Nonsyndromic Hearing Loss and Deafness, DFNB1 (GJB2-Related) Carrier Status report* can tell you whether you may be a carrier for DFNB1. Being a carrier means you have a genetic variant that you could pass down to your future children. 23andMe tests for eight variants in the GJB2 gene linked to DFNB1. 23andMe does not test for all possible genetic variants linked to DFNB1, and individuals who have zero variants detected still have a chance of being a carrier for DFNB1.
The Nonsyndromic Hearing Loss and Deafness, DFNB1 (GJB2-Related) Carrier Status report is included in the 23andMe Health + Ancestry Service.
Health + Ancestry Service
*The 23andMe PGS test uses qualitative genotyping to detect select clinically relevant variants in the genomic DNA of adults for the purpose of reporting carrier status and reporting and interpreting genetic health risks. The relevance of each report may vary based on ethnicity. Our carrier status reports can be used to determine carrier status, but cannot determine if you have two copies of any genetic variant. These carrier reports are not intended to tell you anything about your risk for developing a disease in the future or anything about the health of your fetus, or your newborn child’s risk of developing a particular disease later in life. For certain conditions, we provide a single report that includes information on both carrier status and genetic health risk. The Nonsyndromic Hearing Loss and Deafness, DFNB1 (GJB2-Related) Carrier Status report is indicated for the detection of eight (8) variants in the GJB2 gene. The report can tell you if you have two copies of some tested variants, and if you are at risk of having hearing loss related to DFNB1, but does not describe your overall risk of having DFNB1-related hearing loss. This test is relevant for people of many, but not all, ethnicities. For important information and limitations regarding each carrier status report, visit 23andme.com/test-info.
References
Smith RJH et al. (1998). “Nonsyndromic Hearing Loss and Deafness, DFNB1.” [Accessed Dec 17, 2020].