CPT® Code 81344

TBP (TATA box binding protein) (eg, spinocerebellar ataxia) gene analysis, evaluation to detect abnormal (eg, expanded) alleles

The CPT® Code 81344 pertains to the molecular genetic testing of the TBP (TATA box binding protein) gene, specifically aimed at identifying abnormal alleles that may be expanded. This testing is particularly relevant for conditions such as spinocerebellar ataxia type 17 (SCA17), which is also known as Huntington disease-like 4 (HDL4). SCA17 is a progressive neurodegenerative disorder that primarily affects the cerebellum, the part of the brain responsible for coordinating movement, and may also impact the cerebral cortex and striatum, leading to a range of neurological symptoms. The TBP gene is situated on the long arm of chromosome 6 at position 27 (6q27) and encodes a protein that plays a crucial role in the transcription of DNA into messenger RNA by binding to a specific DNA sequence known as the TATA box. This sequence serves as a critical landmark for the transcription machinery of the cell. The presence of expanded alleles in the TBP gene is associated with the development of symptoms such as uncoordinated movement, emotional instability, and cognitive decline, with symptom onset varying widely from early childhood to late adulthood. The gene features a unique trinucleotide repeat pattern consisting of CAG and CAA sequences, which can repeat multiple times, with expansions beyond 43 repeats being particularly significant in the manifestation of the disease. The analysis coded under 81344 is essential for evaluating these genetic variations and understanding their implications in the context of SCA17/HDL4.