DFNB1 nonsyndromic hearing loss and deafness is an inherited condition in which an individual has mild to severe hearing loss, usually, from birth. Mutations in GJB2 gene (which encodes the protein connexin 26) and muations or deletions in GJB6 gene (which encodes connexin 30) are the main causes of the disease. Typically, the condition does not worsen over time, but in some cases may be slowly progressive. Unlike some other forms of hearing loss, DFNB1 nonsyndromic hearing loss and deafness does not affect balance or movement. The degree of hearing loss is difficult to predict based on which genetic mutation one has. There is variability of the disease severity even among family members carying the same mutation.
Nonsyndromic hearing loss exhibits different inheritance patterns: autosomal recessive (80%), autosomal dominant (20%), X-linked (1%) and mitochondrial (1%).
GJB6 gene (connexin 30) is located in proximity to GJB2 gene (connexin 26) and it harbors mutations as well as gross deletions. Combination of a heterozygous mutation in GJB2 gene and a genetic alteration in GJB6 gene can cause the disease.
The coding region of GJB6 gene (connexin 30) is analysed using bidirectional Sanger sequencing. All possible large deletions in the GJB2/GJB6 complex are analysed using the MLPA technique.
Sample type: Peripheral blood in EDTA
Time to result: 3 weeks