Introduction:
Severity of Cornelia de Lange syndrome (CdLS) based on physical features has been associated with greater neurologic abnormalities and hearing impairment; however, the relationship between CdLS severity and behavioral phenotype has not been well explored.

Methods:
Here, we utilized data collected through the Coordination of Rare Diseases registry at Sanford. Specifically, data from those with an identified gene variant associated with CdLS were included. A total of 13 caregivers of an affected individual with CdLS (Mean age=10.84, SD=8.98, age 3 to 38 years) completed the assortment of inventories assessing medical history, developmental history and behavior functioning to compute an adapted form of the CdLS Severity Criteria (Kline et al. 2007).

Results:
In our sample, approximately 38% of participants had a severe form of CdLS, 46% had moderate involvement and 15% mild severity. Severity of CdLS was associated with greater deficit in verbal communication (r=0.73, p=0.01), and trended towards significance with nonverbal communication (r=0.55, p=0.06), but not a history of self injurious behaviors, behavior regulation, or restrictive and repetitive behaviors, despite controlling for age. Interestingly, when these relationships were explored in small subgroups of those with NIBPL (N=6) and SMC1A (N=5) variants, this pattern was mainly observed among those with the NIPBL variants.

Conclusion:
Preliminary findings suggest severity of the clinical spectrum of CdLS based on physical features may be more intimately linked to select cognitive domains such as communicative functioning, particularly as related to CdLS genotypes.