Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay in Two Half-Siblings.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by biallelic pathogenic variants in the SACS gene. We report the clinical, radiologic and neurophysiologic features of a pair of half-siblings who presented with progressive cerebellar ataxia, peripheral neuropathy and upper motor neuron signs. After significant diagnostic delay, genetic testing revealed both harboured a shared, paternally inherited microdeletion encompassing the SACS gene, and each harboured a different single nucleotide variant in SACS, each likely maternally inherited. Recognition of the clinical and radiologic phenotype of ARSACS may facilitate early diagnosis of this disorder even in the face of uncommon inheritance patterns.