CPT® Code 81187

CNBP (CCHC-type zinc finger nucleic acid binding protein) (eg, myotonic dystrophy type 2) gene analysis, evaluation to detect abnormal (eg, expanded) alleles

The CPT® Code 81187 pertains to the molecular genetic testing of the CNBP (CCHC-type zinc finger nucleic acid binding protein) gene, specifically aimed at identifying mutations associated with myotonic dystrophy type 2. This gene is located on the long (q) arm of chromosome 3 at position 21.3 (3q21.3) and is crucial for producing the CCHC-type zinc finger nucleic acid binding protein, which is predominantly found in heart and skeletal muscle tissues. The CNBP protein features seven zinc finger domains that play a vital role in binding to specific DNA and RNA sites, thereby regulating gene activity. In individuals with myotonic dystrophy type 2, a particular region of the CNBP gene exhibits a tetranucleotide repeat pattern of the sequence CCTG, which typically occurs fewer than 26 times in healthy individuals. However, in affected individuals, this repeat can expand to a minimum of 75 and, in some cases, can reach up to 11,000 repeats. This abnormal expansion leads to the production of an altered form of messenger RNA, resulting in the aggregation of protein molecules within muscle cells, which disrupts normal muscle function. Symptoms of myotonic dystrophy type 2 generally manifest in adulthood and can vary significantly in severity. Common symptoms include progressive muscle wasting and weakness, prolonged muscle contractions (myotonia), cataracts, cardiac arrhythmias, as well as early balding and infertility in males. The code 81187 is utilized to report the analysis of the CNBP gene for the evaluation of these expanded alleles.