CPT® Code 81252

The CPT® Code 81252 pertains to the molecular genetic testing of the GJB2 gene, which encodes the gap junction protein beta 2, also known as connexin 26. This testing is specifically aimed at identifying mutations within the full gene sequence that are responsible for nonsyndromic hearing loss (NSHL). The GJB2 gene plays a critical role in the formation of gap junctions, which are essential for cellular communication, allowing the transport of nutrients, ions, and signaling molecules between adjacent cells. Connexin 26, the protein produced by the GJB2 gene, is particularly important in the inner ear (cochlea) and the epidermis. Located on chromosome 13, the GJB2 gene has been associated with at least 90 identified mutations that can lead to a form of deafness known as NFNB1, which is inherited in an autosomal recessive manner. In this context, an individual who inherits one mutated copy of the gene will be a carrier, while inheriting two mutated copies will result in the manifestation of the condition. The mutations typically disrupt the process by which sound waves are converted into nerve impulses, leading to hearing impairment. Full gene sequence testing, as indicated by CPT® Code 81252, is essential for a comprehensive understanding of the genetic factors contributing to NSHL. In contrast, testing for known familial variants, which may include specific deletions such as 35delG or 30delG, is reported under CPT® Code 81253. These deletions are particularly prevalent in certain populations, with 35delG and 30delG being more common among Caucasians, while 235delC is frequently observed in Asian populations, and 167delT is often found in Ashkenazi Jewish individuals. All these mutations result in the production of an abnormally small protein that fails to effectively bridge the functional gap between cells, leading to hearing loss. Additionally, some mutations may alter amino acids, resulting in unstable or dysfunctional proteins that cannot form proper gap junctions. Another form of hearing loss, DFNA3, is inherited in an autosomal dominant manner and is caused by the replacement of one amino acid with another, where inheriting just one mutated gene is sufficient to cause the disease.