Clinicians' experiences with the fragile X clinical and research consortium

Disease-Targeted Treatment Translation in Fragile X Syndrome as a Model for Neurodevelopmental Disorders

Fragile X syndrome (FXS), the most common monogenic cause of intellectual disability and autism spectrum disorder, has been one of the first neurodevelopmental disorders in which molecular and neuronal mechanisms of disease were identified, leading to the concept of targeting the underlying disease to reverse symptoms. Translating findings in basic science and animal models to humans with FXS has proven difficult. These challenges have prompted the FXS field to organize to build interlocking projects and initiatives to improve consistency of supportive care, make clinical research accessible to families, generate collaborative research on natural history, outcome measures and biomarkers, and create clinical trial consortia and novel trial designs. This work has resulted in improved success in recent clinical trials, providing key steps toward regulatory approval of disease-targeted treatments for FXS. Progress in the FXS field has informed translation of transformative new disease-targeted therapies for other monogenic neurodevelopmental disorders.

Sleep problems in fragile X syndrome: Cross-sectional analysis of a large clinic-based cohort

Fragile X syndrome (FXS), the leading cause of inherited intellectual disability and autism spectrum disorder, is associated with multiple neurobehavioral abnormalities including sleep difficulties. Nonetheless, frequency, severity, and consequences of sleep problems are still unclear. The Fragile X Online Registry with Accessible Research Database (FORWARD-version-3), including Clinician Report and Parent Report forms, was analyzed for frequency, severity, relationship with behavioral problems, and impact of sleep difficulties in a mainly pediatric cohort. A focused evaluation of sleep apnea was also conducted. Six surveyed sleep difficulties were moderately frequent (~23%-46%), relatively mild, affected predominantly younger males, and considered a problem for 7%-20% of families. Snoring was more prevalent in older individuals. All sleep difficulties were associated with irritability/aggression and most also to hyperactivity. Only severe snoring was correlated with sleep apnea (loud snoring: 30%; sleep apnea: 2%-3%). Sleep difficulties are prevalent in children with FXS and, although they tend to be mild, they are associated with behavioral problems and negative impact to families. Because of its cross-sectional nature, clinic-origin, use of ad hoc data collection forms, and lack of treatment data, the present study should be considered foundational for future research aiming at better recognition and management of sleep problems in FXS.

The association between mosaicism type and cognitive and behavioral functioning among males with fragile X syndrome

Mosaicism in fragile X syndrome (FXS) refers to two different FMR1 allele variations: size mosaicism represents different numbers of CGG repeats between the two alleles, such that in addition to a full mutation allele there is an allele in the normal or premutation range of CGG repeats, while methylation mosaicism indicates whether a full-mutation allele is fully or partially methylated. The present study explored the association between mosaicism type and cognitive and behavioral functioning in a large sample of males 3 years and older (n = 487) with FXS, participating in the Fragile X Online Registry with Accessible Research Database. Participants with methylation mosaicism were less severely cognitively affected as indicated by a less severe intellectual disability rating, higher intelligence quotient and adaptive behavior score, and lower social impairment score. In contrast, the presence of size mosaicism was not significantly associated with better cognitive and behavioral outcomes than full mutation. Our findings suggest that methylation mosaicism is associated with better cognitive functioning and adaptive behavior and less social impairment. Further research could assess to what extent these cognitive and behavioral differences depend on molecular diagnostic methods and the impact of mosaicism on prognosis of individuals with FXS.

Fragile X Syndrome: Supportive Treatment, Unmet Needs, and Paths to Novel Interventions and Disease-Targeted Therapies

Fragile X syndrome (FXS), as a monogenic cause of intellectual disability and autism spectrum disorder, has been one of the first neurodevelopmental disorders in which molecular and neuronal mechanisms of disease have been identified, leading to the concept of targeting the underlying disease to reverse symptoms. Translating findings in basic science and animal models to humans with FXS has proven difficult. These challenges have prompted the FXS field to organize to build interlocking projects to support initiatives to improve supportive care, make clinical research accessible to families, generate collaborative research on natural history and outcome measures, and create clinical trial consortia and novel trial designs.

Improving the Diagnosis of Autism Spectrum Disorder in Fragile X Syndrome by Adapting the Social Communication Questionnaire and the Social Responsiveness Scale-2

We carried out a psychometric assessment of the Social Communication Questionnaire (SCQ) and the Social Responsiveness Scale (SRS-2) in fragile X syndrome (FXS), relative to clinician DSM5-based diagnosis of autism spectrum disorder (ASD) in FXS. This was followed by instrument revisions that included: removal of non-discriminating and/or low face validity items for FXS; use of receiver operating characteristic (ROC) curves to determine optimal cut points for the original and revised measures; an exploratory factor analysis to outline subscales better representing ASD in FXS; and creation of a "triple criteria" diagnosis to better delineate ASD subgroups in FXS. These methods improved the sensitivity and/or specificity of the SCQ and SRS-2, but diagnostic accuracy of ASD remains problematic in FXS.

Toilet Training in Fragile X Syndrome

OBJECTIVE

To characterize bladder and bowel toileting skill acquisition in children with fragile X syndrome and to identify associated demographic, behavioral, and clinical factors.

METHODS

Using baseline data from the Fragile X Online Registry With Accessible Research Database (FORWARD), bivariate analyses and logistic regression models were used to identify differences between subjects who were and were not bowel and/or bladder trained by the age of 10 years. Cox proportional hazard models were used to assess the rate of completion of toilet training (TT) as a function of sex and autism spectrum disorder (ASD) diagnosis.

RESULTS

In bivariate analyses, male sex, lower language level, inability to write one's name, more impaired intellectual level, ASD, and more severe behavioral deficits all predicted lack of bladder training (n = 313, p < 0.001) and bowel training (n = 300, p = 0.0004-0.0001) by the age of 10 years. In logistic regression models, lower level of language acquisition (p < 0.001) and higher Aberrant Behavior Checklist Irritability scores (p < 0.04) were associated with lower odds of bladder training by the age of 10 years. Lower level of language acquisition (p < 0.001) and ASD (p < 0.025) were associated with lower odds of bowel training by the age of 10 years. For both bladder and bowel training, Cox proportional hazard models indicated that delayed training was associated with male sex, lower levels of language acquisition, and ASD for both bladder training (n = 486; p < 0.001) and bowel training (n = 472; p < 0.001).

CONCLUSION

These findings emphasize the importance of both slower language development and ASD diagnosis in predicting bowel and bladder training delays and can be used to develop and evaluate targeted approaches to TT based on sex, ASD diagnosis, and other clinical features identified in this study.