USP18 and cat-eye syndrome: To further characterize the origin and gene content of the sSMC, SNP array was performed, the results of which showed a gain of 1.5 Mb in chromosome 22q11.1q11.21 (with a copy number of 4), which contains SLC25A18, IL17RA, BID, XKR3, PEX26, CECR1, MICAL3, CECR2, TUBA8, USP18, and ATP6V1E1 11 Online Mendelian Inheritance in Man (OMIM) genes, of which two (CECR1 and CECR2) are the primary genes associated with cat eye syndrome (CES) (Figure 1D).