From OMIM
The Cornelia de Lange syndrome (CDLS) is a multisystem malformation syndrome recognized primarily on the basis of characteristic facial dysmorphism, including low anterior hairline, arched eyebrows, synophrys, anteverted nares, maxillary prognathism, long philtrum, thin lips, and 'carp' mouth, in association with prenatal and postnatal growth retardation, mental retardation and, in many cases, upper limb anomalies. However, there is wide clinical variability in this disorder, with milder phenotypes that may be difficult to ascertain on the basis of physical features (summary by Rohatgi et al., 2010). Boyle et al. (2015) provided a detailed review of CDLS, including clinical features, diagnosis, and genetic counseling. Genetic Heterogeneity of Cornelia de Lange Syndrome CDLS1, caused by mutation in the NIPBL gene, accounts for about 50 to 60% of CDLS cases (Musio et al., 2006; Rohatgi et al., 2010). X-linked CDLS2 (300590), caused by mutation in the SMC1A gene (300040), accounts for about 5% of cases. CDLS3 (610759) is caused by mutation in the SMC3 gene (606062), and CDLS4 (614701) is caused by mutation in the RAD21 gene (606462). All 4 genes, NIPBL, SMC1A, SMC3, and RAD21, encode components of the cohesin complex. Another X-linked form, CDLS5 (300882), is caused by mutation in the HDAC8 gene (300269), the vertebrate histone deacetylase of SMC3. CDLS6 (620568) is caused by mutation in the BRD4 gene (608749).  http://www.omim.org/entry/122470

From MedlinePlus Genetics
Cornelia de Lange syndrome is a developmental disorder that affects many parts of the body. The features of this disorder vary widely among affected individuals and range from relatively mild to severe.

Cornelia de Lange syndrome is characterized by slow growth before and after birth leading to short stature; intellectual disability that is usually moderate to severe; and abnormalities of bones in the arms, hands, and fingers. Most people with Cornelia de Lange syndrome also have distinctive facial features, including arched eyebrows that often meet in the middle (synophrys), long eyelashes, low-set ears, small and widely spaced teeth, and a small and upturned nose. Many affected individuals also have features similar to autism spectrum disorder, a developmental condition that affects communication and social interaction.

Additional signs and symptoms of Cornelia de Lange syndrome can include excessive body hair (hypertrichosis), an unusually small head (microcephaly), hearing loss, and problems with the digestive tract. Some people with this condition are born with an opening in the roof of the mouth called a cleft palate.  Seizures, heart defects, and eye problems have also been reported in people with this condition.  https://medlineplus.gov/genetics/condition/cornelia-de-lange-syndrome