Symptoms of cerebellar ataxia
Predictive diagnostics in persons at risk in affected families
Prenatal diagnostics in known carriers
Spinocerebellar Ataxia Type 2, SCA2 - ATX2
Spinocerebellar ataxia type 2, SCA 2
Clinical Features
Spinocerebellar ataxias of different types show similar clinical features and are therefore not or hardly distinguishable on clinical grounds. The SCAs typically manifest in adulthood and are clinically characterized by cerebellar gait and limb ataxia, dysarthria and oculomotor disturbances, muscular hypotonia, dysdiadochokinesia, intentional tremor, and extrapyramidal symptoms. Pyramidal signs, participation of the peripheral nervous system (polyneuropathy) and autonomous systems (imperative micturition, impotence, orthostatic dysregulation) may occur (see also Information on SCA1 and SCA3).
Genetic Information
The SCA subtype 2 (chromosome 12q24) is inherited in an autosomal dominant manner and caused by expanded CAG repeats of the SCA gene locus.
An increasing repeat number is statistically associated with an earlier disease onset and more severe symptoms. However, an individual prognosis due to the repeat number is not possible. In SCA2, transmission of the repeat from mother to child usually is stable, in paternal transmission however a repeat expansion with earlier onset of symptoms in the child (anticipation) may occur.
| Repeats | |
| normal allele | < 32 |
| patholigical allele, reduced penetrance |
32 - 33 |
| pathological allele |
≥ 32 |
Diagnostic
Indication
Method
Normal and expanded CAG repeats are detected by PCR and subsequent fragment length analysis.
Sample Requirement
2 - 4 ml of EDTA blood
Duration
approx. 2 weeks