Purpose: The Fragile X Messenger Ribonucleoprotein-1 ( FMR1 ) premutation (FXpm) is a genetic variant that is common in the general population and is associated with health symptoms and disease in adulthood. However, poor understanding of the clinical phenotype during childhood has hindered the development of clinical practice guidelines for screening and intervention. Given that social communication difficulties have been widely documented in adults with the FXpm and are linked with reduced psychosocial functioning, the present study aimed to characterize the communication profile of the FXpm during early childhood. Method: Eighteen children with the FXpm who were identified through cascade testing (89%) or screening at birth (11%) were compared to 21 matched typically developing children, aged 2–4 years. Participants completed standardized assessments of language (Mullen Scales of Early Learning) and adaptive communication (Vineland Adaptive Behavior Scales-II). Social communication was rated from seminaturalistic interaction samples using the Brief Observation of Social Communication Change. Results: Children with the FXpm showed delayed social communication development, with the magnitude of group differences highlighting social communication as a feature that distinguishes children with the FXpm from their peers ( p = .046, η p 2 = .12). The groups did not differ on the standardized language and adaptive communication measures ( p s > .297, η p 2 s < .03). Conclusions: Early screening and treatment of social communication delays may be key to optimizing outcomes for children with the FXpm. Further research is needed to replicate findings in a larger sample, delineate the trajectory and consequences of social communication difficulties across the life span in the FXpm, and determine the potential epidemiological significance of FMR1 as a mediator of developmental communication differences within the general population.
Abstract Background Specifying early developmental differences among neurodevelopmental disorders with distinct etiologies is critical to improving early identification and tailored intervention during the first years of life. Recent studies have uncovered important differences between infants with fragile X syndrome (FXS) and infants with familial history of autism spectrum disorder who go on to develop autism themselves (FH-ASD), including differences in brain development and behavior. Thus far, there have been no studies longitudinally investigating differential developmental skill profiles in FXS and FH-ASD infants. Methods The current study contrasted longitudinal trajectories of verbal (expressive and receptive language) and nonverbal (gross and fine motor, visual reception) skills in FXS and FH-ASD infants, compared to FH infants who did not develop ASD (FH-nonASD) and typically developing controls. Results Infants with FXS showed delays on a nonverbal composite compared to FH-ASD (as well as FH-nonASD and control) infants as early as 6 months of age. By 12 months an ordinal pattern of scores was established between groups on all domains tested, such that controls > FH-nonASD > FH-ASD > FXS. This pattern persisted through 24 months. Cognitive level differentially influenced developmental trajectories for FXS and FH-ASD. Conclusions Our results demonstrate detectable group differences by 6 months between FXS and FH-ASD as well as differential trajectories on each domain throughout infancy. This work further highlights an earlier onset of global cognitive delays in FXS and, conversely, a protracted period of more slowly emerging delays in FH-ASD. Divergent neural and cognitive development in infancy between FXS and FH-ASD contributes to our understanding of important distinctions in the development and behavioral phenotype of these two groups.
Abstract Background Emerging evidence suggests that children with fragile X syndrome (FXS) exhibit abnormal gesture use early in development, although few studies have investigated the emergence of gesture use in this population or the impact of autism spectrum disorder (ASD) features on these behaviours. The present study examined the longitudinal development of gesture use in infants with FXS relative to low‐risk controls and infant siblings of children with ASD (high‐risk siblings), with the goal of establishing potentially unique patterns of gesture development in infants with FXS and understanding the relative impact of ASD symptom severity on these patterns. Method Participants included 86 male infants (39 FXS, 27 high‐risk siblings and 20 low‐risk infants) assessed at 9, 12 and 24 months of age. Multilevel modelling was used to assess differences in number of gestures used and rates of gesture use across groups, as well as the relative impact of ASD symptom severity and nonverbal skills on these patterns. Results Infants with FXS used fewer gestures than high‐risk siblings and low‐risk infants, with this difference being primarily accounted for by the effect of low nonverbal abilities in the FXS group. Furthermore, although higher ASD symptom severity was associated with the use of fewer gestures in both the FXS and high‐risk sibling groups, a significant amount of variance was shared between ASD symptom severity and nonverbal skills in FXS, but not in high‐risk siblings. Conclusions This study presents the first longitudinal analysis of early gesture development in FXS by using a multigroup design, clarifying the relative roles of cognitive deficits and ASD symptom severity in the development of gesture use in FXS. These findings offer novel evidence that early gesture use in FXS may reflect broader features of the FXS phenotype rather than predicting later social‐communicative deficits characteristic of comorbid ASD.
Individuals with Down syndrome (DS) experience deficits across all domains of adaptive functioning, however little is known about the emergence and age‐related changes of these impairments compared to other neurogenetic disorders with similar intellectual disability impairments, such as fragile X syndrome (FXS). Adaptive behavior is key for optimal functioning in these populations. Participants aged 5–45 months comprised three age‐matched groups, DS ( n = 64), FXS ( n = 69), and typically developing controls (TD; n = 69). Adaptive behavior was measured on the Vineland Adaptive Behavior Scales‐II. Regressions were used to examine adaptive behavior in a cross‐sectional design across age. DS infants and toddlers evidenced deficits across all areas of adaptive behaviors compared to the age‐matched TD group, with clear impairments present in the first year of life. Motor skills were the area of greatest weakness in children with DS with significant impairment evident at 12 months of age that remained low through 3 years. Compared to age‐matched children with FXS, children with DS showed initially lower standard scores at 12 months of age, but slower declines in standard scores across age, resulting in less impaired functioning at 36 months. This is the first study to compare adaptive behavior in infants and toddlers with DS to FXS, and demonstrate the phenotypic specificity of adaptive profiles in this diagnostic group. These findings provide evidence that adaptive behavior should be a major target of intervention in children with FXS and DS, and that these differences are potentially driven by unique etiologies attributable to each disorder.
Co-occurring anxiety affects 40-80% of autistic individuals; however, little is understood about how anxiety manifests in young autistic children, especially those with intellectual disability (ID), partly due to the paucity of measures designed to assess anxiety symptoms in this population. The present study examined the utility of the Modified Anxiety Dimensional Observation Scale (M-Anx-DOS), an observational measure of anxiety-related behaviors, in preschool-aged autistic children with and without ID. This study included 48 autistic children (Mean age = 43.96 months; 81.3% with ID) and 30 non-autistic (NA) controls (Mean age = 43.66 months). Anxiety-related behaviors were measured during the M-Anx-DOS. Parent-reported anxiety symptoms were assessed via the Preschool Anxiety Scale-Revised (PAS-R). Groups exhibited comparable scores on both the M-Anx-DOS and PAS-R. Within the autism group, a subset of M-Anx-DOS scores were related to age, autistic features, or IQ. The M-Anx-DOS exhibited excellent inter-rater reliability and acceptable internal consistency. Convergent validity was promising, with specific M-Anx-DOS scores correlated with parent-reported social, separation, and overall anxiety symptoms. M-Anx-DOS scores were not correlated with parent-reported ADHD or externalizing symptoms, suggesting strong discriminant validity. This study provides preliminary evidence of the reliability and validity of the M-Anx-DOS. These findings are promising given the importance of observational measurement of anxiety and lack of existing measures for this critical developmental period. Given the sample size and the complexity of identifying prodromal signs of anxiety in young autistic preschoolers with ID, future longitudinal work is essential to replicate and extend this work.
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