Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (SACS)
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an autosomal recessive disorder that is caused by pathogenic variants in the gene SACS, and has the highest prevalence among the French Canadian population. The clinical presentation includes progressive muscle damage and lack of muscle coordination, peripheral weakness and numbness caused by nerve damage (neuropathy), and muscle spasms (spasticity) in the lower limbs. For individuals of Quebec ancestry, the onset of symptoms usually begins between age 12-18 months with difficulty and unsteadiness while walking. Non-Quebec individuals with ARSACS often do not experience symptoms until later in childhood or adulthood. Other symptoms include involuntary eye movements, loss of sensation due to the progressive nerve damage, deformities of the fingers and feet, difficulties with speech, and yellow streaks in the retina. The cognitive skills of those affected with ARSACS tend to be in the lower range of normal, and while the disease is progressive, most individuals are capable of coping with daily living tasks. No genotype-phenotype correlation is currently known.
For information about carrier frequency and residual risk, please see the residual risk table.