CPT® Code 81173

AR (androgen receptor) (eg, spinal and bulbar muscular atrophy, Kennedy disease, X chromosome inactivation) gene analysis; full gene sequence

The CPT® Code 81173 pertains to the analysis of the androgen receptor (AR) gene, which is crucial for understanding various genetic conditions associated with androgen inactivation syndrome, spinal and bulbar muscular atrophy, Kennedy disease, androgenetic alopecia, and polycystic ovarian syndrome. This molecular genetic testing involves a comprehensive examination of the full gene sequence of the AR gene, located on the long (q) arm of the X chromosome at position 12 (Xq12). The AR gene encodes a protein that binds to androgen hormones, such as testosterone, and plays a significant role in regulating the development of male characteristics during both gestation and puberty. The normal function of the AR gene is characterized by a specific range of trinucleotide CAG (cytosine-adenine-guanine) repeats, typically less than 10 to about 36. However, in conditions like spinal and bulbar muscular dystrophy, these CAG repeats can be expanded to 38 or more, leading to symptoms such as progressive muscle wasting, gynecomastia, testicular atrophy, and fertility issues, predominantly affecting males aged 30 to 60. Mutations in the AR gene can manifest in various ways, including single base pair changes, insertions or deletions of multiple base pairs, or alterations that affect the androgen binding site, resulting in conditions like androgen insensitivity syndrome, which can lead to male feminization. Additionally, small mutations in the AR gene are implicated in androgenetic alopecia, causing hair loss in both males and females. Women with AR gene mutations may also experience symptoms of polycystic ovarian syndrome, including hirsutism, acne, and fertility challenges. The analysis performed under CPT® Code 81173 is essential for identifying functional variants within the AR gene by comparing gene segments to detect similarities or differences, which aids in understanding the genetic underpinnings of these conditions. This comprehensive gene analysis is distinct from other codes, such as 81204, which focuses on allele characterization, and 81174, which targets specific exon sequences for known familial variants.