A de novo 2q35-q36.1 deletion incorporating IHH in a Chinese boy (47,XYY) with syndactyly, type III Waardenburg syndrome, and congenital heart disease

Reports of terminal and interstitial deletions of the long arm of chromosome 2 are rare in the literature. Here, we present a case report concerning a Chinese boy with a 47,XYY karyotype and a de novo deletion comprising approximately 5 Mb between 2q35 and q36.1, along with syndactyly, type III Waardenburg syndrome, and congenital heart disease. High-resolution chromosome analysis to detect copy number variations was carried out using an Affymetrix microarray platform, and the genes affected by the patient's deletion, including IHH, were determined. However, no copy number changes were observed in his healthy parents. The present case exhibited novel syndactyly features, broadening the spectrum of clinical findings observed in individuals with 2q interstitial deletions. Our data, together with previous observations, suggest that IHH haploinsufficiency is the principal pathogenic factor in the syndactyly phenotype in this study, and that different types of variations at the IHH locus may cause divergent disease phenotypes. This is the first report of the involvement of IHH haploinsufficiency in syndactyly phenotype.