FGF14 (Spinocerebellar Ataxia 27B) Repeat Expansion Testing
Description
Pathogenic GAA repeat expansions in the FGF14 gene have been associated with autosomal dominant spinocerebellar ataxia 27B (SCA27B), a late onset ataxia which is considered to be one of the most common SCAs, particularly in the French-Canadian population, though it is also found in other populations.
Pathogenicity is dependent upon GAA repeat length according to the following ranges 1-4:
Normal Alleles | Mutable Normal Alleles | Intermediate/Uncertain Alleles | Reduced Penetrance Alleles | Full Penetrance Alleles |
179 or fewer* | - | 180-249 uninterrupted | 250-300 uninterrupted | 301 or more uninterrupted |
*Larger alleles with non-GAA interruptions are also considered normal and stable.
Note: As SCA27B is typically adult onset, FGF14 repeat expansions are not reported in minors in comprehensive analyses.
Additional Resources
Missed by Others, Found by Us
A 66-year-old male presented with symptoms of ataxia, gait imbalance, dysarthria and gazed-evoked nystagmus. Prior ataxia panel and exome testing was negative. Variantyx testing identified a biallelic FGF14 expansion.
Same Symptoms, Different Diagnoses
Five patients ranging in age from 59-70 presented with similar symptoms of progressive cerebellar ataxia, gait imbalance, progressive sensory neuropathy and dysphagia and/or dysarthria. Each received a different diagnosis with Variantyx testing.
Expanded STR Detection Capability Enables Variantyx to Diagnose Additional Genetic Disorders
Press release: Variantyx, a leader in genomic precision medicine, today announced that the set of short tandem repeat (STR) expansions detected by its Genomic Unity® line of whole genome-based tests has been expanded.