Hemizygous <i>SACS</i> Variant in a Czech Patient With Autosomal Recessive Spastic Ataxia of Charlevoix–Saguenay

ABSTRACT Autosomal recessive spastic ataxia of Charlevoix–Saguenay (ARSACS; MIM 270550) is a rare neurodegenerative disorder caused by pathogenic variants in the SACS gene. We report the case of a 27‐year‐old male patient from the Czech Republic with early‐onset progressive neurological symptoms consistent with ARSACS. Clinical manifestations included delayed motor development, cerebellar ataxia, spastic paraparesis of the lower limbs, and progressive gait impairment. Whole‐exome sequencing identified compound heterozygosity for two pathogenic variants in the SACS gene: a maternally inherited nonsense variant, c.1162C&gt;T, p.(Gln388*), present in a hemizygous state due to a de novo microdeletion encompassing the entire SACS gene on the paternally inherited chromosome. This case expands the molecular spectrum of ARSACS by reporting a novel nonsense variant in a hemizygous state, underscoring the diagnostic value of integrating sequence and copy number analysis derived from WES data in patients with hereditary spastic ataxia.