Strong Genetic

Nonsyndromic Hearing Loss (DFNB1)

Name: Nonsyndromic Hearing Loss (DFNB1)
Creator: Realised
Published: 2026-03-01

GeneGJB2rsIDrs80338939, rs80338943, rs80338945InheritanceAutosomal recessiveCarrier frequency~1 in 33 Europeans (35delG), ~1 in 20 Ashkenazi Jewish (167delT), ~1 in 50 East Asian (235delC)SystemCarrier Screening

Summary

DFNB1 is the most common genetic cause of hearing loss, responsible for roughly half of all congenital hearing loss worldwide. Variants in GJB2 disrupt connexin 26, a protein that forms gap junctions in the inner ear essential for recycling potassium ions after sound stimulation. Affected children are typically born with moderate to profound hearing loss in both ears. Crucially, this is non-syndromic — only hearing is affected, with no other organ involvement. Cochlear implants are highly effective, and early detection paired with early intervention leads to near-normal language development.

Practical takeaway

This matters when planning children. If your partner has no known family history of hearing loss, their chance of also being a carrier depends on ancestry — roughly 1 in 33 for Europeans, higher for Ashkenazi Jewish individuals. A simple carrier test through a GP or genetic counselling service can clarify your partner's status. If you are both carriers, a genetic counsellor can walk you through what that means practically — including newborn hearing screening timelines and intervention options. Realised does not calculate reproductive risk or advise on reproductive decisions.

Evidence detail

What Carrier Status Means For You

You are not affected. Carrying one working copy of GJB2 is sufficient for normal hearing. Your carrier status becomes relevant if you and your partner both carry a GJB2 variant — in that case, each child has a 25% chance of being born with hearing loss, a 50% chance of being an unaffected carrier like you, and a 25% chance of inheriting neither variant.

Population Context

GJB2 carrier rates vary significantly by ancestry because different founder mutations became common in different populations. The 35delG variant is most frequent in Europeans and traces to a single ancestral event roughly 10,000 years ago. The 167delT variant is common in Ashkenazi Jewish communities. The 235delC variant predominates in East Asian populations. These patterns reflect population history, not health disparities — carrier frequency simply tracks which founder mutation became established in which geographic region.

Limitations

23andMe tests 8 of over 200 known pathogenic GJB2 variants. The tested panel covers the most common variants in European, Ashkenazi Jewish, and East Asian populations but may miss rarer variants, particularly those prevalent in African, South Asian, or other populations. A "not detected" result does not eliminate carrier risk — it reduces it based on the variants tested. Comprehensive carrier screening through a clinical laboratory covers substantially more variants and is recommended if family planning decisions depend on this result.

Sources (5)

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