CeGaT is setting a new standard in ataxia diagnostics by offering a rare test for FGF14 repeat expansion, which is crucial for diagnosing spinocerebellar ataxia type 27B (SCA27B). Standard sequencing methods fail to detect pathogenic FGF14 expansions, leaving cases undiagnosed. CeGaT is now one of only four providers worldwide offering a diagnostic test to address this gap.
Overcoming the challenge in SCA27B testing
SCA27B is a rare, adult-onset neurodegenerative disorder primarily affecting gait coordination and progressing slowly over time. Symptoms may be episodic or triggered by alcohol or physical exertion. The condition’s cause lies in an abnormal repeat expansion in the DNA. A repeat is a DNA base sequence that occurs multiple times in a row. In SCA27B, the GAA repeat (Guanine, Adenine, Adenine) expands abnormally, increasing the number of copies beyond a pathogenic threshold.
Detecting pathogenic expansions is highly challenging, as the repeat length and purity determine whether the expansion is harmful. In SCA27B, pathogenicity occurs when the GAA sequence expands beyond 300 repeats. Expansions between 250 and 300 GAA are considered likely pathogenic but have low penetrance. Non-pure expansions — where the GAA sequence is interrupted — are typically not pathogenic, regardless of size.
Because standard short-read sequencing methods fail to detect these pathogenic expansions, many cases remain undiagnosed or are identified too late. To close this critical gap, CeGaT has developed a specialized test that accurately identifies FGF14 repeat expansions, ensuring reliable diagnoses.
CeGaT’s approach
Our advanced test combines long-range PCR, capillary electrophoresis, and agarose gel electrophoresis for sizing. Repeat-primed PCR then confirms the suspected SCA27B diagnosis. With this approach, physicians can confidently diagnose SCA27B and make informed treatment decisions.
The FGF14 repeat expansion analysis complements our comprehensive diagnostics portfolio for neurodegenerative diseases. Based on our ExomeXtra® enrichment and with flexible panel options, such as tests for other repeat disorders, CeGaT‘s Panel for Neurodegenerative Diseases provides a stepwise approach to precise genetic diagnostics.
Contact our diagnostic experts at +49 (0) 7071 565 44 55 or diagnostic-support@cegat.com to determine the best strategy for your patients.