A new case of interstitial 6q16.2 deletion in a patient with Prader-Willi-like phenotype and investigation of SIM1 gene deletion in 87 patients with syndromic obesity.

The association of obesity, phenotypic abnormalities and mental retardation characterizes syndromic obesity. Its most common form is the Prader-Willi syndrome (PWS-- neonatal hypotonia, poor sucking, delayed psychomotor development, hyperphagia, severe obesity, short stature, small hands and feet, hypogonadism, mild to moderate mental retardation and behavioral disorders). A PWS-like phenotype has been described in patients with chromosome abnormalities involving the chromosome region 6q16.2 that includes the SIM1 gene. Herein we report cytogenetic and gene studies including a screening for the SIM1 gene deletion, performed on 87 patients with PWS-like phenotype, and describe the fifth case of syndromic obesity with an interstitial deletion of the chromosome segment 6q16-q21 and suggest that mutational analysis and further studies of the parental origin of chromosome alterations of 6q16.2 in patients with and without PWS-like phenotype are needed to evaluate possible imprinting effects of SIM1 gene and establish the contribution that alterations in this gene makes to the etiology of syndromic and non-syndromic obesity.