Introduction: Autism spectrum disorder (ASD) is one of the most prevalent neurodevelopmental disorders and has a major genetic heterogeneity. Comparing monogenetic causes of ASD can contribute to...Show moreIntroduction: Autism spectrum disorder (ASD) is one of the most prevalent neurodevelopmental disorders and has a major genetic heterogeneity. Comparing monogenetic causes of ASD can contribute to understanding its genetic aetiology. This study compares patients with fragile X syndrome (FXS) to patients with tuberous sclerosis complex (TSC) in terms of ASD severity and symptomatology to create an image of their ASD symptom profiles. This could lead to more focused diagnoses and specialized treatment for these patient groups. Methods: This study included children and adolescents (ages 1–18, mean age = 9.01 years) with FXS (n = 57, 80.7% males) or TSC (n = 105, 49.5% males). The second editions of the Autism Diagnostic Observation Scale and the Social Responsiveness Scale were used to assess ASD symptomatology. First, the prevalence of official ASD diagnoses among FXS and TSC patients was compared. Next, patients with an official diagnosis were compared in terms of (1) overall autism severity, (2) severity of problems within the restricted and repetitive behaviour (RRB) and social affect domains, and (3) more specific ASD symptoms such as ‘reciprocal communication’. Intelligence quotient (IQ; mean IQ = 58.08) was included as a predictor in the logistic regression and as a covariate in both between-group analyses of covariance and all multivariate analyses of covariance. Results: FXS patients are more likely to receive an official ASD diagnosis (χ2 = 4.081, p = .043). Higher IQ is related to less autism symptomatology (χ2 = 8.592, p = .003). Overall, ASD severity of patients with an official ASD diagnosis does not differ between the patient groups. The FXS patients with ASD exhibited more severe RRB (F = 8.21, p = .005). No significant difference was found for social affect or any specific symptoms. Conclusion: ASD prevalence is higher in children with FXS than in children with TSC, with FXS patients exhibiting more severe RRB. This study illustrates the relevance of comparing symptomatology in monogenetic causes of ASD, indicating that syndrome-symptom relationships can be found. This could lead to earlier intervention and focused treatment for these patients and contributes to research on the genetic aetiology of ASD.Show less
