Potocki-Shaffer syndrome (PSS) is a rare disorder caused by haploinsufficiency 
of genes located on the proximal short arm of chromosome 11 (11p11.2p12). 
Classic features include biparietal foramina, multiple exostoses, profound 
hypotonia, dysmorphic features, and developmental delay/intellectual disability. 
Fewer than 40 individuals with PSS have been reported, with variable clinical 
presentations due in part to disparity in deletion sizes. We report on a boy who 
presented for initial evaluation at age 13 months because of a history of 
developmental delay, hypotonia, subtle dysmorphic features, and neurobehavioral 
abnormalities. SNP microarray analysis identified a 137 kb deletion at 11p11.2, 
which maps within the classically defined PSS interval. This deletion results in 
haploinsufficiency for all or portions of six OMIM genes: SLC35C1, CRY2, 
MAPK8IP1, PEX16, GYLTL1B, and PHF21A. Recently, translocations interrupting 
PHF21A have been associated with intellectual disability and craniofacial 
anomalies similar to those seen in PSS. The identification of this small 
deletion in a child with developmental delay and hypotonia provides further 
evidence for the genetic basis of developmental disability and identifies a 
critical region sufficient to cause hypotonia in this syndrome. Additionally, 
this case illustrates the utility of high resolution genomic approaches in 
correlating clinical phenotypes with specific genes in contiguous gene deletion 
syndromes.