CPT® Code 81285

The CPT® Code 81285 pertains to the molecular genetic testing of the FXN (frataxin) gene, which is specifically associated with Friedreich ataxia, a progressive neuromuscular disorder characterized by a range of debilitating symptoms. The FXN gene is located on the long (q) arm of chromosome 9 at position 21.11 (9q21.11) and plays a crucial role in coding for a protein that is essential for iron metabolism, antioxidant protection, and energy production within the body. This protein is distributed throughout various tissues, with the highest concentrations found in the heart, spinal cord, liver, pancreas, and skeletal muscles. Friedreich ataxia manifests through a variety of symptoms, including impaired balance and coordination, decreased strength and sensation in the extremities, muscle stiffness and spasticity, as well as potential speech, hearing, and visual impairments. Additionally, individuals may experience hypertrophic cardiomyopathy, diabetes, and scoliosis. The onset of symptoms typically occurs between the ages of 5 and 15 in approximately 75% of cases, while the remaining 25% may not exhibit symptoms until after the age of 25. The FXN gene is notable for its unique DNA allele, which consists of a trinucleotide repeat pattern of three amino acids: glycine, alanine, and alanine (GAA). In healthy individuals, this repeat occurs fewer than 33 times, with short normal alleles having fewer than 12 repeats and long normal alleles ranging from 12 to 33 repeats. In most affected individuals, two (homozygous) genes will exhibit expanded trinucleotide repeats located on intron 1 of the FXN gene. A small percentage, about 2%, may present with one gene having expanded trinucleotide repeats while the other gene may contain a point mutation or deletion. The analysis performed under CPT® Code 81285 is critical for characterizing these expanded alleles, determining their size, and identifying any similarities or differences, which can provide valuable insights into the genetic underpinnings of Friedreich ataxia.