Autosomal dominant cerebellar ataxia

Autosomal dominant cerebellar ataxia (ADCA), also known as spinocerebellar ataxia (SCA), encompasses a large and heterogeneous group of neurodegenerative disorders characterized by progressive cerebellar dysfunction inherited in an autosomal dominant pattern. These conditions primarily affect the cerebellum — the part of the brain responsible for coordinating movement and balance — but frequently involve other parts of the nervous system as well, including the brainstem, spinal cord, peripheral nerves, and in some subtypes, the basal ganglia and cerebral cortex. More than 40 genetic subtypes have been identified (SCA1, SCA2, SCA3/Machado-Joseph disease, SCA6, SCA7, SCA17, etc.), many caused by trinucleotide repeat expansions, while others result from conventional point mutations or other genetic mechanisms. The hallmark symptom is progressive gait and limb ataxia, meaning patients develop increasing difficulty with walking, balance, and coordination of voluntary movements. Additional features vary by subtype but commonly include dysarthria (slurred speech), dysphagia (difficulty swallowing), oculomotor abnormalities (such as nystagmus and slow saccades), pyramidal signs (spasticity, hyperreflexia), peripheral neuropathy, and cognitive impairment. Some subtypes have distinctive features: SCA7 is associated with progressive retinal degeneration leading to visual loss, while SCA3 may present with prominent dystonia and bulging eyes. Harding's classification historically divided ADCAs into three types: ADCA type I (cerebellar ataxia with additional neurological features), ADCA type II (cerebellar ataxia with retinal degeneration), and ADCA type III (pure cerebellar ataxia). Onset is typically in adulthood, though age of onset varies considerably both between and within subtypes, ranging from childhood to late adulthood. The disease course is generally progressive over years to decades, often leading to significant disability including wheelchair dependence and eventually premature death. There is currently no cure or disease-modifying therapy for most forms of ADCA. Management is supportive and symptomatic, including physical therapy, occupational therapy, speech therapy, and assistive devices to maintain function and quality of life. Genetic counseling is essential for affected families. Research into antisense oligonucleotides and gene-silencing therapies is ongoing for several subtypes.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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