PNKP and Friedreich ataxia: The most frequent were SACS, KIF1C, and PNKP. To note, Friedreich ataxia, AOA (AOA1 and 2) and L-2-hydroxyglutaric aciduria had been previously screened and found to be the most prevalent types of AR-HCA [10]; KIF1C and PNKP were described only a few years later to be the causative genes for SPAX2 and AOA4 [11,39].