CPT® Code 81337

The CPT® Code 81337 pertains to the molecular genetic testing of the SMN1 (survival of motor neuron 1, telomeric) gene, specifically focusing on known familial sequence variant(s) associated with spinal muscular atrophy (SMA). SMA is a degenerative neuromuscular disease that is often fatal, characterized by the progressive loss of motor neurons in the spinal cord and brainstem, 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 crucial role in producing a protein essential for the survival of motor neurons. This protein facilitates the transport of signals from motor neurons to voluntary muscles, which are vital for functions such as walking, talking, and swallowing. In addition to the SMN1 gene, the SMN2 (survival of motor neuron 2, centromeric) gene may also be analyzed, as it is closely related and can influence the severity of SMA. The SMN1 gene is responsible for producing 85-90% of the functional protein, while the SMN2 gene contributes the remaining 10-15%, albeit with only one of its isoforms being fully functional. The presence of multiple copies of these genes can affect the risk of SMA transmission to offspring, with individuals potentially having between 0 to 3 copies of the SMN1 gene and up to 8 copies of the SMN2 gene. The analysis performed under CPT® Code 81337 is particularly significant when there is a known family history of SMA, as it allows for the identification of specific mutations that have already been documented in other family members. This targeted approach helps in assessing the risk for at-risk family members and provides valuable information for genetic counseling and family planning. Overall, this code is essential for understanding the genetic underpinnings of spinal muscular atrophy and for guiding clinical decisions based on familial genetic information.