LAUSR

Purpose The behavioral phenotype of fragile X syndrome (FXS) and intellectual disability (ID) proposed by Hagerman et al. (2009) was primarily based on data from male children and teens. The purpose of this study was to promote a better understanding of how this condition manifests in adults. Design/methodology/approach A total of 18 men of FXS were paired with men with Down syndrome on the basis of age and level of ID. A screening checklist was created on the basis of existing scales and the Hagerman et al. (2009) behavioral phenotype and completed by care providers. Findings Five of the 12 features of the phenotype were significantly more present among men with FXS than in men with Down syndrome. Originality/value This study provides partial confirmation for Hagerman et al.’s (2009) behavioral phenotype of FXS among men with moderate ID and identified some traits that warrant further investigation.