ABSTRACT
The prevalence of X-linked mental retardation (XLMR) is approximately 1.8 males per 1000. The most common form of XLMR is fragile X syndrome (FXS), which is a syndromic form of XLMR. The behavioral phenotype can be the most important clue leading to the diagnosis of FXS. The behavioral phenotype is marked by the association of four main features: hyperarousal, attention deficit hyperactivity disorder, social anxiety, and autism. A variety of medical problems occur in the first year of life and require medical intervention. Many infants with FXS or non-specific XLMR present with hypotonia and motor delays either at birth or in the first year of life. Anxiety is a significant problem in FXS, and it is related to sensory hyperarousal. Medication intervention includes the use of selective serotonin reuptake inhibitors, although only survey information is available regarding efficacy.
