PEARLS >Gerstmann-Straussler-Scheinker disease (GSS) is a rare prion disease characterized by cerebellar ataxia with progressive cognitive decline. >GSS is caused by a mutation within the prion protein gene (PRNP), which commonly exhibits autosomal dominant inheritance pattern. However, a significant portion of previously reported cases showed no family history of the disease, and GSS may also occur through de novo mutation of PRNP. OY-STERS >GSS is clinically heterogeneous and has no characteristic features on imaging. GSS could be considered in patients experiencing unexplained ataxia and subsequent cognitive decline even in those without a family history of the disease.