Case of 15q26-qter deletion associated with a Prader-Willi phenotype.

Abstract Prader-Willi syndrome (PWS) is one of the common neurogenetic disorders associated with intellectual disability. PWS involves a complex inheritance pattern and is caused by an absence of gene expression on the paternally inherited 15q11.2-q13 region, either due to deletion, maternal uniparental disomy or imprinting defect. The syndrome is characterized principally by severe neonatal hypotonia, a weak suck in infancy that is later followed by hyperphagia and obesity, developmental delay, intellectual disability and short stature. In the case of the chromosome 15q26-qter deletion syndrome or Drayer's syndrome, very few reports have been published. Its characteristics include intrauterine growth restriction, postnatal growth failure, varying degrees of intellectual disability, developmental delay, typical facial appearance and diaphragmatic hernia. The present paper describes a female patient in whom clinical findings were suggestive of PWS and deletion in the 15q26-qter region. Both karyotyping and methylation-specific polymerase chain reaction were shown to be normal. Nevertheless, fluorescence in situ hybridization showed a 15qter deletion that was later mapped by single nucleotide polymorphism (SNP)-array. The deleted genomic region involves the insulin-like growth factor-1 receptor (IGF1R) gene, which is related to short stature, developmental delay and intellectual disability. This case had various clinical characteristics in common with the cases of 15q26-qter deletionand characteristics compatible with PWS.