My son is only 4.5 He was diagnosed at birth with Mosaic Down Syndrome, Mosaic Klinefelter syndrome and still has normal cells present that aren't affected by either syndrome. He's the only known person with that genetic makeup. So far he hasn't showed any outward symptoms that we've noticed. He has not seen a specialist either. They said he didn't need monitored until he started puberty which I hope is true since he's never been seen.