title: Birth seasonality in Korean Prader-Willi syndrome with chromosome 15 microdeletion.
abstract: OBJECTIVE
  Prader-Willi syndrome (PWS) is a well-known genetic disorder, and microdeletion on chromosome 15 is the most common causal mechanism. Several previous studies have suggested that various environmental factors might be related to the pathogenesis of microdeletion in PWS. In this study, we investigated birth seasonality in Korean PWS.
  
  
  METHODS
  A total of 211 PWS patients born from 1980 to 2014 were diagnosed by methylation polymerase chain reaction at Samsung Medical Center. Of the 211 patients, 138 were born from 2000-2013. Among them, the 74 patients of a deletion group and the 22 patients of a maternal uniparental disomy (UPD) group were compared with general populations born from 2000 using the Walter and Elwood method and cosinor analysis.
  
  
  RESULTS
  There was no statistical significance in seasonal variation in births of the total 211 patients with PWS (χ(2)=7.2522, P=0.2982). However, a significant difference was found in the monthly variation between PWS with the deletion group and the at-risk general population (P<0.05). In the cosinor model, the peak month of birth for PWS patients in the deletion group was January, while the nadir occurred in July, with statistical significance (amplitude=0.23, phase=1.2, low point=7.2). The UPD group showed the peak birth month in spring; however, this result was not statistically significant (χ(2)=3.39, P=0.1836).
  
  
  CONCLUSIONS
  Correlation with birth seasonality was identified in a deletion group of Korean PWS patients. Further studies are required to identify the mechanism related to seasonal effects of environmental factors on microdeletion on chromosome 15.
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Aram
authors.initials: A
authors.lastname: Yang
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Yeon Hee
authors.initials: YH
authors.lastname: Lee
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Soon Young
authors.initials: SY
authors.lastname: Nam
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Yu Ju
authors.initials: YJ
authors.lastname: Jeong
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Yechan
authors.initials: Y
authors.lastname: Kyung
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Rimm
authors.initials: R
authors.lastname: Huh
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jieun
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Younghee
authors.initials: Y
authors.lastname: Kwun
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Sung Yoon
authors.initials: SY
authors.lastname: Cho
authors.affiliation: Department of Pediatics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Dong-Kyu
authors.initials: DK
authors.lastname: Jin
keywords: Birth; Microdeletion; Prader-Willi syndrome; Seasonality