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Spinocerebellar Ataxia Panel (SCA1, 2, 3, 6, 7, 12, 17)
Blood
Report in 192Hrs
At Home
No Fasting Required
Details
Genetic panel for SCA.
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Spinocerebellar Ataxia Panel (SCA1, 2, 3, 6, 7, 12, 17)
- Why is it done?
- Detects mutations in genes associated with spinocerebellar ataxias (SCA), a group of inherited neurological disorders characterized by progressive loss of coordination and muscle control
- Evaluates patients presenting with progressive ataxia, gait disturbance, dysarthria, nystagmus, or other cerebellar dysfunction symptoms
- Identifies individuals with family history of ataxia or hereditary neurological disorders
- Confirms suspected diagnosis of spinocerebellar ataxia when clinical features suggest genetic ataxia
- Enables genetic counseling and reproductive risk assessment in affected families
- Typically performed when patients present with progressive cerebellar ataxia and family history or when imaging excludes acquired causes
- Normal Range
- Normal Result (Negative): No pathogenic mutations detected in any of the seven SCA genes tested (SCA1, SCA2, SCA3, SCA6, SCA7, SCA12, SCA17); normal CAG repeat numbers within expected range for each gene
- Normal CAG Repeat Ranges:
- SCA1: <45 CAG repeats
- SCA2: <33 CAG repeats
- SCA3: <44 CAG repeats
- SCA6: <19 CAG repeats
- SCA7: <37 CAG repeats
- SCA12: <66 CAG repeats
- SCA17: <42 CAG repeats
- Positive Result (Abnormal): Pathogenic CAG repeat expansion detected in one or more SCA genes; repeats exceed upper limit for normal range
- Borderline/Intermediate Results: CAG repeats in intermediate or reduced penetrance range; may be reported separately with recommendation for genetic counseling and possible monitoring
- Units: Number of CAG trinucleotide repeats in affected genes
- Interpretation
- Pathogenic Mutation Detected:
- Indicates confirmed diagnosis of spinocerebellar ataxia (SCA1, SCA2, SCA3, SCA6, SCA7, SCA12, or SCA17)
- CAG repeat length may correlate with age of onset (earlier onset with larger expansions) and disease severity
- Each SCA type presents with distinct clinical features; specific gene mutation helps guide prognosis and management
- No Mutation Detected:
- Excludes SCA1, 2, 3, 6, 7, 12, and 17; other genetic causes or acquired ataxia should be considered
- May recommend testing for other SCA types (SCA5, SCA10, SCA11, etc.) or alternative genetic/metabolic investigations
- Intermediate/Reduced Penetrance Alleles:
- May not cause disease in the individual but could expand to pathogenic levels in offspring
- Genetic counseling recommended to discuss reproduction risks and family implications
- Factors Affecting Interpretation:
- Anticipation: CAG repeats may expand in successive generations, leading to earlier onset and more severe phenotype in offspring
- Somatic mosaicism: Repeat number may vary slightly between different tissues
- Genetic background and modifying genes: May influence age of onset and disease progression
- Homozygous mutations: Rare but may result in more severe phenotype
- Associated Organs
- Primary Organ Systems Involved:
- Cerebellum: Primary site of neurodegeneration; responsible for coordination and balance
- Brainstem: Often affected; leads to dysarthria and oculomotor dysfunction
- Spinal cord: Pyramidal and dorsal column pathways affected; causes weakness and sensory changes
- Peripheral nervous system: Neuropathy and myopathy may occur depending on SCA type
- Common Conditions Associated with Abnormal Results:
- Progressive cerebellar ataxia with gait disturbance, dysarthria, and coordination loss
- Nystagmus and oculomotor abnormalities
- Cognitive decline and dementia (variable by SCA type)
- Parkinsonism and movement disorders (some SCA types)
- Retinal degeneration and progressive vision loss (SCA7 particularly)
- Psychiatric manifestations including depression and anxiety
- Potential Complications of Abnormal Results:
- Severe disability and loss of independence with disease progression
- Falls, injuries, and increased fracture risk
- Dysphagia and aspiration risk with associated pneumonia
- Cardiac arrhythmias and conduction abnormalities (some SCA types)
- Genetic implications for family members with inheritance risk
- Follow-up Tests
- Recommended Based on Positive Results:
- Neurological examination and assessment: Detailed evaluation of ataxia severity, functional status, and disease progression
- Brain MRI: Assess for cerebellar atrophy and other structural changes characteristic of SCA type
- Ophthalmological evaluation: Especially for SCA7 which includes progressive retinal degeneration
- Cognitive assessment and neuropsychological testing: Evaluate for dementia and cognitive decline
- Electrocardiogram (ECG): Screen for cardiac conduction abnormalities and arrhythmias if indicated
- Genetic counseling: Comprehensive discussion of diagnosis, prognosis, inheritance pattern, and family implications
- Expanded SCA panel or sequencing: If negative, test for other SCA types (SCA4, SCA5, SCA8, SCA10, SCA11, etc.)
- Further Investigations:
- Whole exome or whole genome sequencing: Consider if SCA panel negative but clinical suspicion remains high
- Functional MRI and advanced neuroimaging: Research and prognostic studies
- Metabolic and toxicology screening: If presenting features atypical for SCA
- Family Testing and Monitoring:
- Cascade genetic testing: First-degree relatives should be offered testing if desired, after genetic counseling
- Presymptomatic testing: Asymptomatic carriers may opt for testing; longitudinal monitoring recommended
- Monitoring Frequency:
- Annually: Neurological assessment and evaluation of disease progression
- Every 2-3 years: Neuroimaging (MRI) to assess structural changes and disease progression
- As clinically indicated: Symptomatic management and specialist referrals (neurology, ophthalmology, cardiology, etc.)
- Fasting Required?
- Fasting Required: No
- This is a genetic test performed on a blood sample that is not affected by fasting status, food intake, or nutritional state
- Patient Preparation:
- No special preparation needed
- Patient may eat and drink normally before the test
- No medications need to be discontinued
- Sample Collection:
- Blood sample collected via venipuncture (standard blood draw) into appropriate EDTA or other anticoagulant tube
- Sample processed for DNA extraction and genetic analysis
- Special Instructions:
- Informed consent: Important to obtain informed consent as this is genetic testing with significant implications for patient and family
- Genetic counseling: Recommended before testing to discuss risks, benefits, limitations, and psychological implications
- Genetic counseling recommended after testing: To discuss results and implications, particularly for positive findings
- Turnaround time: Typically 2-4 weeks depending on laboratory and testing complexity
How our test process works!
