A new isolated 20q interstitial duplication case and its clinical comparison with similar isolated cases: Duplications of 20q are rare. Here we report a 15 years old boy with de novo duplication of 17.1Mb at chromosome 20q. We made a comparison with the other isolated 20q duplication cases. There are phenotypic similarities between the patients who have the same affected chromosomal regions. We also showed a clinical follow up of the patient. There may be a relationship with Glaucoma and Graves disease between the chromosomal region and these diseases may occur at the other patients when they get older.