de novo interstitial deletions at the 11q23.3-q24.2 region.

Background: Jacobsen syndrome (JBS) is a contiguous gene deletion syndrome involving 11q terminal deletion. Interstitial deletions at distal 11q are rare and their contributions to the clinical phenotype of JBS are unknown.

Case Presentation: We presented the chromosome microarray (CMA) data and the clinical features of two individuals carrying a non-overlapping de novo deletion each at the 11q23.3-q24.2 region in an effort to analyze the correlation between region of deletion at 11q and phenotype. Both deletions are likely pathogenic for patient's condition. The deletion at 11q23.3q24.1 is associated with short stature, relative microcephaly, failure to thrive, hypotonia and sleeping disorder. The deletion at 11q24.2 involves HEPACAM and our patient's clinical presentation (relative macrocephaly, abnormal MRI, mild developmental delay and seizure) is not inconsistent with Megalencephalic leukoencephalopathy with subcortical cysts 2B.

Conclusions: Our finds support the notion that more than one critical region at 11q23.3-qter are responsible for the variable clinical presentation of JBS, thus JBS is a true contiguous gene deletion syndrome where multiple loci contributed to the clinical characteristics of JBS. Small interstitial deletions at 11q23.3-q24.2 and their associated unique features also suggest emerging novel genomic disorders.