Infantile-onset spinocerebellar ataxia

Infantile-onset spinocerebellar ataxia (IOSCA), also known as OHAHA syndrome (ophthalmoplegia, hypoacusis, ataxia, hypotonia, and athetosis), is a rare hereditary neurodegenerative disorder that primarily affects the nervous system. It is caused by mutations in the C10orf2 gene (also known as TWNK), which encodes the mitochondrial helicase Twinkle, essential for mitochondrial DNA replication. IOSCA was first described in the Finnish population, where it is most prevalent due to a founder effect. The disease typically manifests between 1 and 2 years of age in children who previously appeared to develop normally. Key clinical features include progressive cerebellar ataxia (loss of coordination), peripheral neuropathy (sensorimotor), ophthalmoplegia (impaired eye movements), sensorineural hearing loss, and hypotonia. As the disease progresses, patients may develop epileptic seizures, optic atrophy, and athetoid movements. The ataxia worsens over time, and most affected individuals lose the ability to walk independently. Cognitive function may also decline, and some patients develop liver involvement. The central and peripheral nervous systems, as well as the auditory and visual systems, are primarily affected. There is currently no cure or disease-modifying treatment for IOSCA. Management is supportive and symptomatic, including physical therapy to maintain mobility, hearing aids or cochlear implants for hearing loss, antiepileptic medications for seizure control, and occupational therapy. Regular monitoring by a multidisciplinary team including neurologists, audiologists, and ophthalmologists is recommended. The prognosis is variable, but the disease is generally progressive, with significant disability developing during childhood and adolescence.

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