Restricted Repetitive Behaviors of Individuals with Comorbid Tuberous Sclerosis Complex and Autism Spectrum Disorder

Background: While atypical language development is the most common area of first concern for children with ASD, restricted repetitive behaviors (RRBs) may be some of the first manifestations of ASD, often presenting prior to language development (Wolff et al., 2014). Children with ASD of varying cognitive and adaptive abilities have significantly greater frequency and severity of RRBs compared to typically developing children (Ozonoff et al.,2008; Wolff et al.,2014). In infancy, children with ASD are likely to display repetitive motor movements including rocking, hand flapping, and unusual posturing (Wolff et al.,2014; Harrop et al.,2014; Ozonoff et al.,2008; Richler et al.,2010). By age 3 years, children with ASD also display unusual sensory preoccupations or interests.

There has been increasing interest in examining ASD within genetic disorders (Moss et al.,2012) such as tuberous sclerosis complex (TSC; McDonald et al.,2017; Jeste et al.,2014; Sundberg & Sahin,2015). However, caregivers and clinicians frequently do not recognize the proper diagnosis as being ASD in individuals with TSC (Capal et al.,2017), as RRBs are not well characterized within the TSC population. Better understanding of RRBs in individuals with TSC, as well as those with comorbid TSC and ASD, may inform earlier diagnosis of ASD, promoting optimal outcomes.

Objectives: The current study aims to examine and define the presence of RRBs in individuals with TSC and ASD.

Methods: Participants included 129 children with TSC participating in a multisite longitudinal study through the TSC Autism Center of Excellence Network. Within this sample, 26 individuals received an ASD diagnosis and 103 did not have ASD. Cognitive ability was assessed via the Mullen Scales of Early Learning, adaptive functioning via the Vineland Adaptive Behavior Scales-Second Edition, and RRBs via the Autism Diagnostic Interview-Revised (ADI-R).

Results: Groups did not significantly differ on age or gender(p’s>0.05). The ASD group had significantly lower cognitive (t(26.5)=-3.14,p<.001) and adaptive scores (t(93)=-4.65,p<.001). Overall, the ASD group had significantly higher scores on ADI-R Total Restricted, Repetitive, and Stereotyped Patterns of Behaviors(p<0.05). Further, the ASD group showed significantly higher scores on C1-Encompassing Preoccupations or Circumscribed Patterns of Interest, C3-Stereotyped and Repetitive Motor Mannerisms, and C4-Preoccupation with Parts of Objects or Nonfunctional Elements of Materials (p’s<0.05). At the item level, the ASD group showed significantly higher scores on Unusual Preoccupations, Hand and Finger Mannerisms, Other Complex Mannerisms or Stereotyped Body Movements, Repetitive Use of Objects, and Unusual Sensory Interests (p’s<0.05). Groups did not differ on Circumscribed Interests, Verbal Rituals, or Compulsions/Rituals.

Conclusions: Results suggest that individuals with TSC and ASD have overall increased amounts and severity of RRBs, specifically increased unusual preoccupations, hand/finger and other complex mannerisms, repetitive use of objects, and unusual sensory interests. This suggests that children with TSC and ASD have a similar RRB profile to children with ASD only at 3 years of age (Wolff et al.,2014; Harrop et al.,2014; Ozonoff et al.,2008; Richler et al.,2010). As such, this profile may aid in detecting individuals with ASD within the TSC population at an earlier age, allowing for better detection of affected individuals.