Our results indicate that genes present in PARs in sex chromosomes, particularly including ASMTL, ZBED1, AKAP17A, CD99, CSF2RA, DHRSX, and SLC25A6, and those evading XCI, including KDM5C, KDM6A, EIF1AX, and DDX3X, which are biallelically expressed under normal conditions, potentially account for some clinical features of TS and KS. This evidence concerns the gene CD99 and Timothy syndrome.