CPT® Code 81336

The CPT® Code 81336 pertains to the molecular genetic testing of the SMN1 (survival of motor neuron 1, telomeric) gene, specifically focusing on the full gene sequence analysis. This testing is crucial for diagnosing spinal muscular atrophy (SMA), a severe neuromuscular disorder characterized by the degeneration of motor neurons, leading to muscle weakness and atrophy. The SMN1 gene, located on the long arm of chromosome 5 at position 13.2 (5q13.2), plays a vital role in producing a protein essential for the survival of motor neurons. This protein facilitates the transmission of signals from the nervous system to voluntary muscles, which are responsible for critical functions such as walking, talking, and swallowing. In addition to the SMN1 gene, the analysis may also involve the SMN2 (survival of motor neuron 2, centromeric) gene, which, while similar, produces a less functional protein. The SMN1 gene is responsible for approximately 85-90% of the protein required by the body, whereas the SMN2 gene contributes the remaining 10-15%. The presence of multiple copies of these genes can influence the severity of SMA and the risk of transmission to offspring. In most cases, SMA is caused by deletion mutations in both copies of the SMN1 gene, while a smaller percentage of cases involve one deletion mutation and another type of mutation that disrupts gene function. The full gene sequence analysis provided by CPT® Code 81336 allows for a comprehensive examination of the SMN1 gene, identifying functional variants and assessing the genetic markers associated with SMA. This detailed analysis is essential for understanding the genetic underpinnings of the disease and for informing potential treatment options and family planning considerations.