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Review
, 33 (5), 379-94

What Can We Learn About Autism From Studying Fragile X Syndrome?

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Review

What Can We Learn About Autism From Studying Fragile X Syndrome?

Dejan B Budimirovic et al. Dev Neurosci.

Abstract

Despite early controversy, it is now accepted that a substantial proportion of children with fragile X syndrome (FXS) meets diagnostic criteria for autism spectrum disorder (ASD). This change has led to an increased interest in studying the association of FXS and ASD because of the clinical consequences of their co-occurrence and the implications for a better understanding of ASD in the general population. Here, we review the current knowledge on the behavioral, neurobiological (i.e., neuroimaging), and molecular features of ASD in FXS, as well as the insight into ASD gained from mouse models of FXS. This review covers critical issues such as the selectivity of ASD in disorders associated with intellectual disability, differences between autistic features and ASD diagnosis, and the relationship between ASD and anxiety in FXS patients and animal models. While solid evidence supporting ASD in FXS as a distinctive entity is emerging, neurobiological and molecular data are still scarce. Animal model studies have not been particularly revealing about ASD in FXS either. Nevertheless, recent studies provide intriguing new leads and suggest that a better understanding of the bases of ASD will require the integration of multidisciplinary data from FXS and other genetic disorders.

Figures

Fig. 1
Fig. 1
Diagram of the relationship between skills and ASD in FXS. Note that the delay in socialization skills, and not in overall cognitive or language skills, is a selective contributor to the diagnosis and severity (measured as ADI-R/ADOS-G scores) of ASD in FXS. Rec = Receptive; Exp = expressive; lang = language skills; ADI-R = Autism Diagnostic Interview-Revised [36]; ADOS-G = Autism Diagnostic Observation Schedule-Generic [45] (see fig. 4.1, p. 87, in Kaufmann et al. [57]). Reprinted with kind permission of Springer Science + Business Media.
Fig. 2
Fig. 2
Model of the relationships between social withdrawal, cognitive impairment, social anxiety, and ASD in FXS. Note that either severe social withdrawal (SSW: SW-I or SW-S) per se or mild social withdrawal (MSW) in conjunction with lower nonverbal skills would lead to social anxiety (SA). A more complex combination of deficits, specifically the addition of lower socialization or verbal skills, is required for ASD alone or comorbid with social anxiety. SSW = Severe social withdrawal; SW-I = social withdrawal-intermediate; SW-S = social withdrawal-severe; MSW = mild social withdrawal; SA = social anxiety (see fig. 4.2, p. 88, in Kaufmann et al. [57]). Reprinted with kind permission of Springer Science + Business Media.

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