Birth seasonality in Korean Prader-Willi syndrome with chromosome 15 microdeletion

Abstract

Purpose: 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).

Conclusion: 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.

Keywords: Birth; Microdeletion; Prader-Willi syndrome; Seasonality.

Fig. 1. Monthly distribution of births of patients with Prader-Willi syndrome. In the total group of 138 patients, March was the peak month, with 18 patients (13%). In the deletion group, birth rate was highest in January and March; each month had 11 patients (14.86%). In contrast, the lowest birth rate was seen in June and July (3 patients each; 4%). In the UPD group, there was no apparent systematic distribution. Total, total patients with PWS; Del, microdeletion group; UPD, maternal uniparental disomy group.

Fig. 2. Seasonal distribution of births of patients with Prader-Willi syndrome (PWS). The peak season of PWS in the deletion group was winter,with 23 patients (31%); summer was the lowest, with 10 patients (13%). For the total of 138 patients with PWS (birth year: 2000-2013), spring was a peak season with 39 patients (28%), and summer was the lowest, with 28 patients (20%). In the uniparental disomy (UPD) group, peak season was spring, with seven patients (31%), and trough season was autumn, with four patients (18%). The relationship between the PWS group (deletion, mUPD, total) and seasonality was not statistically significant (chi-square test, P=0.2982). Spring (March-May), summer (June-August), autumn (September-November), winter (December-February). Total, total patients with PWS; Del, microdeletion group; UPD, maternal uniparental disomy group.