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Macrocephaly in autism and other pervasive developmental disorders
D J Fidler1, J N Bailey, S L Smalley
1UCLA Neuropsychiatric Institute, Los Angeles, CA, USA.
Insights
Children with autism show higher rates of macrocephaly, a larger head circumference, and this trait appears to be familial. This suggests macrocephaly may be a risk factor in the development of autism.
Area of Science:
- Neurodevelopmental disorders
- Genetics and heritability
Background:
- Macrocephaly, defined as a head circumference significantly larger than average, is observed in various neurodevelopmental conditions.
- The prevalence and familial contribution of macrocephaly in autism spectrum disorder (ASD) require further investigation.
Purpose of the Study:
- To determine the prevalence of macrocephaly in children with autism and related pervasive developmental disorders.
- To assess the familial aggregation of head circumference in families of children with autism.
- To compare macrocephaly rates in autism with a comparison group with tuberous sclerosis complex (TSC) or seizure disorders.
Main Methods:
- A study involving 41 children diagnosed with autism and 21 children with TSC or unspecified seizure disorders.
- Head circumference measurements were taken for probands and 133 first-degree relatives to assess familiality.
- Statistical comparison with published normative data and within the study groups.
Main Results:
- Macrocephaly was significantly more prevalent in children with autism (12.2%) and their first-degree relatives (15.5%) compared to normative data.
- The comparison group with TSC/seizure disorders also showed higher than normative rates (9.5% in probands, 8.3% in relatives), but the association was stronger in autism.
- Head circumference and extreme macrocephaly scores demonstrated moderate heritability (H2 = 0.47).
Conclusions:
- The elevated prevalence of macrocephaly in relatives of children with autism suggests it may be a familial risk factor in autism's pathogenesis.
- Macrocephaly is a heritable trait that is disproportionately associated with autism spectrum disorder.
- These findings highlight the potential role of genetic factors influencing head growth in the development of autism.
Abstract:
To assess the prevalence of macrocephaly (head circumference > or = 1.88 standard deviations above normative data for age and sex or > 97th centile) in autism and other pervasive developmental disorders, 41 children with autism, and a comparison group of 21 children with tuberous sclerosis complex (TSC) or an unspecified seizure disorder were studied. Familiality of head circumference was also assessed from measurements of 133 first-degree relatives. Significantly higher rates of macrocephaly were found in probands with autism (12.2%) and their first-degree relatives (15.5%) when compared against a published normative sample. The incidence of macrocephaly in the comparison group of probands with TSC and seizure disorder (9.5%) and their first-degree relatives (8.3%) was higher than normative data as well, although the relation between macrocephaly and autism was more pronounced. Head circumference and extreme scores reflecting macrocephaly were moderately heritable in the present sample (H2 = 0.47). The increased prevalence of macrocephaly in relatives of children with autism compared with control children suggests that this characteristic may be a familial risk factor in the pathogenesis of autism.
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