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%).
Nonsyndromic hearing loss accounts for about 40% of cases with hearing loss among children. More than 30 genes have been connected to the development of the disease, however approximately 65% of cases are due to mutations in GJB2 gene (connexin 26).
The most frequent mutation of GJB2 gene is 35delG, which is detected in more than 90% of cases.
The analysis is carried out using ARMS-PCR to detect the c.35delG mutation in GJB2 (connexin 26) gene.
Sample type: Peripheral blood in EDTA
Time to result: 1 week
There is the possibility of prenatal screening for 35delG mutation in chorionic villi or amniotic fluid samples.