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| Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disorder with an incidence of approximately 1 in 20,000. SCA1 is characterized by progressive ataxia, dysarthria, amyotrophy, and bulbar dysfunction. Anticipation occurs within SCA1 families, and generally SCA1 is adult onset; however, juvenile onset can occur. A molecular analysis is available for a complex differential diagnosis suggesting SCA1. The mutation responsible for SCA1 resides in the ataxin-1 gene which maps to 6p22-p23 and is characterized by expansion of an unstable CAG trinucleotide repeat. Normal individuals have 36 or fewer repeats, while SCA1 patients have expansions of 45 repeats or greater. Correlations of length of the repeat with age of onset of disease are not precise enough to be used clinically. Reasons for Referral:
We recommend that genetic and/or psychological counseling be made available to all patients considering having confirmatory or predictive testing for SCA1. Testing Methodology:Direct Mutation Analysis: PCR analysis across the CAG region of the SCA1 gene to determine allele sizes. All normal sized alleles and the vast majority of expanded alleles will be detected in this analysis. Southern analysis is used to identify extremely large CAG repeat expansions. Allele-size ranges are subject to change as more information becomes available. Specimen Requirements:
Blood: EDTA (purple-top) tubes: Adults: 14 cc; Child: 6
cc; Infant: 2-3 cc Turnaround Time:3 weeks CPT Codes and Prices:83898, 83891, 83892, 83894x2, 83896, 83897, 83912 Shipping InformationForms: >> DNA
Requisition Test Codes:
Index: 6054 |