CPT® Code 81343

PPP2R2B (protein phosphatase 2 regulatory subunit Bbeta) (eg, spinocerebellar ataxia) gene analysis, evaluation to detect abnormal (eg, expanded) alleles

Molecular genetic testing is a critical procedure used to identify specific genetic abnormalities associated with various disorders. In the case of CPT® Code 81343, the focus is on the PPP2R2B gene, which encodes the protein phosphatase 2 regulatory subunit Bbeta. This gene is particularly relevant in the context of spinocerebellar ataxia type 12 (SCA12), a neurodegenerative condition that primarily affects the cerebellum, the part of the brain responsible for coordinating movement. The PPP2R2B gene is situated on the long (q) arm of chromosome 5 at position 32 (5q32) and plays a significant role in regulating cell growth and division through its protein product. The symptoms associated with SCA12 include a progressive loss of coordination in both gait and hand movements, the presence of action tremors, difficulties with hand-eye coordination, and in some cases, the emergence of pyramidal and extrapyramidal symptoms, as well as dementia. These symptoms typically begin to manifest in individuals between the ages of 40 and 50, although they can appear as early as age 8 and as late as age 55. The genetic analysis performed under this code specifically looks for abnormal alleles of the PPP2R2B gene, characterized by an expanded CAG repeat sequence. Normally, this sequence consists of 7 to 28 repeats; however, in individuals with SCA12, this repeat can expand to between 55 and 78 repeats. The identification of these abnormal alleles is crucial for diagnosis and understanding the genetic basis of the disorder.