The Prader-Willi phenotype of fragile X syndrome

J Dev Behav Pediatr. 2007 Apr;28(2):133-8. doi: 10.1097/01.DBP.0000267563.18952.c9.


The Prader-Willi phenotype (PWP) of fragile X syndrome (FXS) is associated with obesity and hyperphagia similar to Prader-Willi syndrome (PWS), but without cytogenetic or methylation abnormalities at 15q11-13. Thirteen cases of PWP and FXS are reported here that were identified by obesity and hyperphagia. Delayed puberty was seen in 5 of 9 cases who had entered puberty, a small penis or testicles in seven of 13 cases, and infant hypotonia and/or a poor suck in seven of 13 cases. Autism spectrum disorder occurred in 10 of 13 cases, and autism was diagnosed in seven of 13 cases. We investigated cytoplasmic interacting FMR1 protein (CYFIP) expression, which is a protein that interacts with FMR1 protein (FMRP) because the gene for CYFIP is located at 15q11-13. CYFIP mRNA levels were significantly reduced in our patients with the PWP and FXS compared to individuals without FXS (p < .001) and also individuals with FXS without PWP (p = .03).

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adolescent
  • Adult
  • Autistic Disorder / diagnosis
  • Autistic Disorder / genetics
  • Child
  • Child, Preschool
  • Chromosomes, Human, Pair 15 / genetics
  • Fragile X Mental Retardation Protein / genetics
  • Fragile X Syndrome / diagnosis
  • Fragile X Syndrome / genetics*
  • Gene Expression Regulation / physiology
  • Humans
  • Male
  • Phenotype*
  • Prader-Willi Syndrome / diagnosis
  • Prader-Willi Syndrome / genetics*
  • Puberty, Delayed / diagnosis
  • Puberty, Delayed / genetics
  • RNA, Messenger / genetics


  • Adaptor Proteins, Signal Transducing
  • CYFIP1 protein, human
  • FMR1 protein, human
  • RNA, Messenger
  • Fragile X Mental Retardation Protein