Amelioration of the typical cognitive phenotype in a patient with the 5pter deletion associated with Cri-du-chat syndrome in addition to a partial duplication of CTNND2

Cri-du-chat is a rare congenital syndrome characterized by intellectual disability, severe speech/developmental delay, dysmorphic features, and additional syndromic findings. The etiology of this disorder is well known, and is attributed to a large deletion on chromosome 5 that typically ranges from band 5p15.2 to the short arm terminus. This region contains CTNND2, a gene encoding a neuronal-specific protein, delta-catenin, which plays a critical role in cellular motility and brain function. The exact involvement of CTNND2 in the cognitive functionality of individuals with Cri-du-chat has not been fully deciphered, but it is thought to be significant. This report describes an 8-year-old African-American female with a complex chromosome 5 abnormality and a relatively mild case of cri-du-chat syndrome. Because of the surprisingly mild cognitive phenotype, although a karyotype had confirmed the 5p deletion at birth, an oligo-SNP microarray was obtained to further characterize her deletion. The array revealed a complex rearrangement, including a breakpoint in the middle of CTNND2, which resulted in a partial deletion and partial duplication of that gene. The array also verified the expected 5p terminal deletion. Although the patient has a significant deletion in CTNND2, half of the gene (including the promoter region) is not only preserved, but is duplicated. The patient's milder cognitive and behavioral presentation, in conjunction with her atypical 5p alteration, provides additional evidence for the role of CTNND2 in the cognitive phenotype of individuals with Cri-du-chat.