SNP Shot: Genomic Insights

Infantile-onset spinocerebellar ataxia (IOSCA) is a neurodegenerative condition that worsens over time. Infants with IOSCA initially develop as expected for the first year. However, in early childhood, they begin to show signs of impaired coordination (ataxia), reduced muscle tone (hypotonia), involuntary limb movements (athetosis), and diminished reflexes. By adolescence, individuals with IOSCA typically need a wheelchair.

IOSCA frequently causes issues with the autonomic nervous system, which regulates involuntary bodily processes. This can lead to symptoms such as excessive sweating, difficulty with bladder control, and severe constipation.

Vision and hearing impairments also occur in IOSCA, usually starting around age 7. Affected children develop weakness in the eye muscles (ophthalmoplegia). During their teenage years, they may experience optic atrophy (degeneration of the optic nerves), potentially causing vision loss. Sensorineural hearing loss, resulting from nerve damage, usually begins in childhood and progresses to profound deafness.

Seizures (epilepsy) are common in individuals with IOSCA. These seizures can lead to significant brain impairment (encephalopathy).

Most individuals with IOSCA live into adulthood. However, a small number experience a particularly severe form of IOSCA characterized by liver damage and encephalopathy in early childhood, and their lifespan is typically limited to around 5 years.

Inheritance:

IOSCA is inherited in an autosomal recessive manner. This means that both copies of the relevant gene in each cell must be mutated for the condition to manifest. Individuals with autosomal recessive disorders inherit one mutated copy of the gene from each parent, who are typically carriers but do not exhibit symptoms of the condition themselves.