SNP Shot: Genomic Insights

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a disorder that primarily affects motor skills. Individuals with ARSACS commonly experience muscle stiffness (spasticity), impaired balance and coordination (cerebellar ataxia), and diminished sensation along with weakness in the limbs (peripheral neuropathy).

Furthermore, ARSACS can manifest as muscle atrophy (amyotrophy), uncontrolled eye movements (nystagmus), and difficulties in swallowing (dysphagia) and speech (dysarthria). Other characteristics associated with ARSACS may include high arches in the feet (pes cavus), a curved spine (scoliosis), the presence of yellowish fatty streaks in the retina (hypermyelination of the retina), urinary problems, cognitive impairment, hearing impairment, and recurring seizures (epilepsy).

The initial indication of ARSACS is typically an unstable manner of walking (gait). Difficulties with walking usually appear between 12 and 18 months of age, coinciding with the period when toddlers are learning to walk. These motor impairments progress with time, leading to greater spasticity and ataxia in the arms and legs. In some instances, spasticity may seem to lessen, but this apparent improvement is believed to stem from nerve atrophy in the extremities. A majority of affected individuals require wheelchair assistance by their third or fourth decade of life.

Although named after the Charlevoix-Saguenay region of Quebec, Canada, where it was initially observed, ARSACS has since been diagnosed in people across the globe.

Inheritance:

ARSACS is inherited in an autosomal recessive manner. This means that for a person to develop the condition, they must inherit a mutated copy of the responsible gene from each parent. The parents, who each carry only one copy of the mutated gene, usually do not exhibit any symptoms of the condition themselves.