BACKGROUND: Klinefelter's syndrome is a sex chromosome abnormality affecting 
approximately 1 in 1000 men. There have been suggestions that it is associated 
with a higher than average prevalence of sexual offending but to what extent 
does research evidence support this assertion?
AIMS: This study aimed to conduct a systematic review of published research to 
establish the prevalence of sexual offending in men with Klinefelter's syndrome.
METHOD: The databases MEDLINE, PsycINFO and EMBASE were searched from inception 
until 31 December 2016 by using a range of terms for Klinefelter's syndrome and 
for sexual offending. All selected papers were examined for quality by using the 
Strengthening the Reporting of Observational Studies in Epidemiology checklist.
RESULTS: We identified 53 relevant papers of which 10 met our inclusion 
criteria. All but one were prevalence studies conducted in a prison or hospital 
setting. The one, Danish, register-based cohort study did suggest an increased 
risk of sex offending among Klinefelter men, probably established before the 
diagnosis was made and, therefore, any hormone replacement instituted.
CONCLUSION: There is insufficient evidence to date to support concerns about 
exceptional risk of sex offending among men with Klinefelter's syndrome. Rather, 
it is arguable that there is a research gap in understanding how the experience 
of and treatment for their condition may affect them. Copyright © 2017 John 
Wiley & Sons, Ltd.