title: Prevalence of Prader-Willi syndrome among infants with hypotonia.
abstract: OBJECTIVE
  To investigate the prevalence of Prader-Willi syndrome (PWS) in infants with hypotonia between the ages of 0 and 2 years.
  
  
  METHODS
  Karyotyping studies were performed in all infants with hypotonia. The study group was composed of infants with hypotonia for whom the karyotyping was found to be normal. Fluorescence in situ hybridization and methylation analysis were performed simultaneously in the study group. Molecular studies for uniparental disomy were undertaken in the patients without deletions with an abnormal methylation pattern.
  
  
  RESULTS
  Sixty-five infants with hypotonia with a mean age of 8 months were enrolled. A deletion was detected in 6 patients by fluorescence in situ hybridization analysis. Only 1 patient had no deletion but had an abnormal methylation pattern. A maternal uniparental disomy was observed in this patient. PWS was diagnosed in 10.7 % (7/65) of the infants with hypotonia.
  
  
  CONCLUSIONS
  The prevalence of PWS syndrome is high among infants with hypotonia. PWS should be considered by pediatricians and neonatologists in the differential diagnosis of all newborns with hypotonia. Early diagnosis of PWS is important for the management of these patients.
authors.affiliation: Department of Pediatric Genetics, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey. Electronic address: beyhantuysuz@yahoo.com.
authors.forename: Beyhan
authors.initials: B
authors.lastname: Tuysuz
authors.affiliation: Department of Pediatric Genetics, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: Nuray
authors.initials: N
authors.lastname: Kartal
authors.affiliation: Department of Neonatology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: Tugba
authors.initials: T
authors.lastname: Erener-Ercan
authors.affiliation: Department of Genetics, Institute for Experimental Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Filiz
authors.initials: F
authors.lastname: Guclu-Geyik
authors.affiliation: Department of Neonatology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Vural
authors.affiliation: Department of Neonatology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: Yildiz
authors.initials: Y
authors.lastname: Perk
authors.affiliation: Department of Pediatric Genetics, Dokuzeylul University, İzmir, Turkey.
authors.forename: Derya
authors.initials: D
authors.lastname: Erçal
authors.affiliation: Department of Genetics, Institute for Experimental Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Nihan
authors.initials: N
authors.lastname: Erginel-Unaltuna
mesh_terms: D002675:Child, Preschool; D019175:DNA Methylation; D003937:Diagnosis, Differential; D005260:Female; D005820:Genetic Testing; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009123:Muscle Hypotonia / Q000209:etiology*; D011218:Prader-Willi Syndrome / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D015995:Prevalence; D017384:Sequence Deletion