- Hereditary ataxias are caused by repeat expansions in specific genes.
- Testing for repeat expansions is recommended before Next-Generation Sequencing (NGS) analysis.
- Key clinical features often include cerebellar ataxia and other systemic manifestations.
- MRI findings can assist in the diagnosis by revealing characteristic patterns of atrophy.
- The spectrum of spinocerebellar ataxias (SCAs) varies widely in clinical features, onset age, and genetic causes.
- Repeat expansion size influences severity and associated systemic manifestations.
Friedreich's Ataxia (FA)
- Gene: FXN
- Pathological Expansion:
- FA: >700 GAA repeats
- LOFA (Late-Onset FA): <500 GAA
Cerebellar Ataxia, Neuropathy, and Vestibular Areflexia Syndrome (CANVAS)
- FA: 7–25 years
- LOFA: 25–40 years
- VLOFA (Very Late-Onset FA): >40 years
Spinocerebellar Ataxia Type 3 (SCA3)
- FA: Sensory neuropathy, cerebellar ataxia, absent tendon reflexes, Babinski sign, scoliosis, pes cavus, impaired position and vibratory senses, hearing loss, optic neuropathy, diabetes, cardiomyopathy.
- LOFA & VLOFA: Normal tendon reflexes, Babinski sign, spastic ataxia.
Spinocerebellar Ataxia Type 2 (SCA2)