SCA-17 (SPINOCEREBELLAR ATAXIA): TBP GENE MUTATION

SCA17 IS AN AUTOSOMAL DOMINANT NEUROLOGIC DISORDER CHARACTERIZED BY ATAXIA, PYRAMIDAL AND EXTRAPYRAMIDAL SIGNS, COGNITIVE IMPAIRMENTS, PSYCHOSIS, AND SEIZURES. ANTICIPATION IN SCA17 IS UNCOMMON DUE TO THE INTERRUPTED CONFIGURATION OF THE REPEAT ALLELES, WHICH RESULTS IN STABILIZATION DURING INTERGENERATIONAL TRANSMISSION. IT CAN BE CAUSED BY HETEROZYGOUS EXPANSION OF A TRINUCLEOTIDE REPEAT ENCODING GLUTAMINE (CAG OR CAA) IN THE TATA BOX-BINDING PROTEIN (TBP; 600075). RARELY, SCA17 HAS BEEN FOUND TO BE CAUSED BY HOMOZYGOUS OR COMPOUND HETEROZYGOUS TBP REPEAT EXPANSIONS.