Mutations in SMC1A (OMIM 300040) and SMC3 (OMIM 606062) also give rise to syndromes that fall within the CdLS spectrum, and account for about 5% of CdLS cases (Musio et al., 2006; Deardorff et al., 2007; Mannini et al., 2010). The gene discussed is SMC1A; the disease is Cornelia de Lange syndrome.