Cornelia de Lange Syndrome (CdLS) is a rare developmental disorder that is present from birth. The syndrome was named after the Dutch children’s doctor Cornelia de Lange, who first described the disorder in 1933. It is estimated that between 1 in 10,000 and 1 in 30,000 people in the population have CdLS.

CdLS can affect many parts of the body and individuals with CdLS may display physical, cognitive and behavioural characteristics. Cognitive characteristics are brain-based processes like memory and thinking. Behavioural characteristics refer to certain behaviours that individuals with CdLS are more likely to have. These characteristics can vary widely among affected individuals and range from small differences compared to other people to very noticeable differences.