Prevalence of Autism Spectrum Disorder in Turner Syndrome
Approximately 16-23% of patients with Turner Syndrome meet diagnostic criteria for Autism Spectrum Disorder, representing a four-fold increased risk compared to the general population.
Evidence from Population-Based Studies
The most robust evidence comes from a large Swedish population-based cohort study of 1,392 females with Turner Syndrome, which demonstrated a fourfold increased risk of autism spectrum disorder (OR 4.26,95% CI 2.94-6.18) compared to age- and sex-matched controls 1. This represents one of the largest and highest-quality epidemiological assessments of this association.
A more recent clinical study using standardized diagnostic assessments (DAWBA) found that 23% of children and adolescents with Turner Syndrome met full diagnostic criteria for ASD, with 83% experiencing significant social communication difficulties 2. This study is particularly compelling because it used rigorous diagnostic instruments rather than registry data alone.
Karyotype-Specific Considerations
The mechanism underlying this increased ASD risk relates to sex chromosome effects, specifically the absence of a second X chromosome 3. The evidence suggests:
- The protective effect of having two X chromosomes is lost in Turner Syndrome (45,X karyotype) 3
- Girls with 45,X karyotype show lower full-scale IQ compared to other Turner Syndrome karyotypes, though this did not reach statistical significance after correction for multiple comparisons 4
- The female-protective effect hypothesis posits that a second X chromosome normally protects against ASD, explaining why Turner Syndrome patients have elevated rates 3
Clinical Screening Implications
Routine neuropsychological assessment should specifically screen for ASD in all Turner Syndrome patients, particularly given that:
- 34% have at least one mental health or neurodevelopmental condition 2
- Those with ASD have higher rates of co-occurring emotional disorders and ADHD 2
- 16% prevalence was found in a diverse clinical sample undergoing routine neuropsychological testing 4
- An eightfold increased risk of intellectual disability (OR 8.59,95% CI 6.58-11.20) further complicates the clinical picture 1
Additional Psychiatric Comorbidities
Beyond ASD, Turner Syndrome patients face elevated risks for:
- ADHD (26% prevalence) 4
- Anxiety disorders (26% prevalence) 4
- Specific learning disorder in mathematics (18% prevalence) 4
- Schizophrenia and related disorders (OR 1.98) 1
- Eating disorders (OR 2.03) 1
The high prevalence of ASD and other neurodevelopmental conditions in Turner Syndrome necessitates early screening at key developmental transitions, ideally beginning in preschool years and continuing through adolescence 2, 4. This allows for appropriate behavioral interventions and educational accommodations to be implemented when they are most effective.