Diagnosis in children with physical and intellective anomalies is very challenging because of the wide spectrum of causes. Array-based comparative genomic hybridization (CGH) has acquired an important role in pediatric diagnostic work up. Interstitial deletion of the long arm of chromosome 12 are rare. To date, deletions including the 12q21 region were reported in only 13 patients. The main features are development delay, eyes and central nervous system anomalies, and heart and kidney defects. We describe a 3-year-old boy with a de novo 15 Mb deletion at 12q21.1q21.32, never reported in the last cases. By screening the critical region and reviewing the literature, we identified SYT1, PPP1R12A, and CEP290 such as pathogenetic genes.