In contrast, patients with the second most frequent phenotype are homozygous for valine at codon 129 of the PRNP gene, accumulate Type 2 PrPSc and manifest a different disease course, with early ataxia, predominant extra-pyramidal symptoms, relatively late-onset dementia in the extended course of the disease, and large plaque-like deposits of PrPSc[21]. The gene discussed is PRNP; the disease is dementia.