Nonsyndromic Hearing Loss and Deafness: DFNB1: GJB6 related

Nonsyndromic Hearing Loss and Deafness DFNB1 is an inherited disorder that only affects hearing. No other medical problems are associated with the hearing loss. DFNB1 is present at birth and does not worsen over time; however, the severity of the hearing loss varies among individuals. Hearing loss for individuals with DFNB1 can be helped with the use of hearing aids or the possibility of cochlear implants for those with profound deafness. In 98% of cases, the hearing loss is caused by two pathogenic variants in the GJB2 gene, while 2% of cases are due to pathogenic variants in GJB2 and another gene named GJB6.

DFNB1 is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant in the gene for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. Both parents must be carriers of a pathogenic variant in either GJB2 or GJB6 genes, or a combination of both genes in order to be at risk to have a child with DFNB1. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

There are generally no signs or symptoms associated with being a carrier for DFNB1. However, the risk to have a child affected with DFNB1 is increased. Testing of reproductive partners is recommended for carriers of DFNB1.

In the United States, DFNB1 accounts for about 50% of congenital, severe-to-profound, autosomal recessive nonsyndromic hearing loss. Its occurrence worldwide is variable.

Genetics Home Reference: Nonsyndromic deafness (http://ghr.nlm.nih.gov/)

OMIM [DFNB1A: 220290] (http://www.ncbi.nlm.nih.gov/omim)
Gene Reviews: Nonsyndromic Hearing Loss and Deafness, DFNB1 (http://www.ncbi.nlm.nih.gov/books/NBK1116/)

• Copy number analysis: 5'-upstream and exons 2 & 3