Spinocerebellar ataxia
What is Spinocerebellar Ataxia?
Spinocerebellar ataxia (Ataxia in Greek means disorder) is a rare genetic neurological disease that are characterized by degenerative changes in the part of brain which results in worsening of movement and coordination. Spinocerebellar ataxia (SCA) usually begins at the age of 18 years.
Most common subtypes of spinocerebellar ataxia:
- SCA Type 1 (Shut's disease)
- SCA Type 2
- SCA Type 3 (Machado-Joseph disease)
- SCA Type 6
- SCA Type 7
Frequency of occurrence: 2:100000
Heredity: autosomal dominant
Description of the DNA test
Spinocerebellar ataxia DNA test tests for changes in the number of trinucleotide CAG repeats in genes:
- ATXN1 (SCA type 1) - encodes protein ataxin 1,
- ATXN2 (SCA type 2) - encodes protein ataxin 2,
- ATXN3 (SCA type 3) - encodes protein ataxin 3,
- CACNA1A (SCA type 6) - encodes calcium voltage-gated channel subunit alpha1A,
- ATXN7 (SCA type 7) - encodes protein ataxin 7.
Interpretation of results
Interpretation of CAG trinucleotide repeats of ATXN1, ATXN2, ATXN3, CACNA1A and ATXN7 genes:
- Normal allele of the ATXN1 gene: <36 CAG repeats without insertions. <44 CAG repeats with CAT insertion;
- Normal allele of the ATXN2 gene: <31 CAG repeats with or without insertions;
- Normal allele of the ATXN3 gene: <40 CAG repeats;
- CACNA1A gene normal allele: <18 CAG repeats;
- Normal allele of the ATXN7 gene: <19 CAG repeats.
What if a DNA test confirms a diagnosis of spinocerebellar ataxia?
In cases when a tested gene mutation is detected in a patient, we recommend to consult a neurologist. The family would also be advised to consult a geneticist to determine the risk of the disease and the status of the mutation carrier, especially for close family members.