We are looking for research participants with Cornelia de Lange syndrome and/or genetic changes in the following genes: ANKRD11, BRD4, CTCF, ESCO1, ESCO2, ESPL1, HDAC8, LEMD2, LMNB1, MAU2, NAA10, NIPBL, OTUD5, PDS5A, PDS5B, RAD21 (SCC1), REC8, SATB2, SGO1, SMC1A, SMC3, STAG1, STAG2, STAG3, WAPL, and YY1. If you or your family member has Cornelia de Lange syndrome and/or a genetic change (variant, mutation, deletion, or duplication) in one of these genes you may be eligible to participate in this study.