Using the Autism Dysmorphology Measure (ADM), children with Autism Spectrum Disorders (ASD) may be categorized into either “complex” or “essential” autism. Individuals with complex autism are differentiated from essential autism by the presence of microcephaly and/or dysmorphology. Previous studies with moderate sample sizes have found differences between complex and essential autism for certain developmental and medical markers. The complex subgroup was found to have lower IQ scores, poorer response to behavioral intervention, more seizures, and more abnormal EEGs and brain MRIs compared to the essential subgroup.
Objectives: The objective of this study is to determine if there are differences in complex vs. essential subjects based on developmental profile (cognitive level, adaptive behavior, autism severity, quality of life, and behavioral ratings) as well as medical comorbidities (GI symptomatology, sleep problems and medication usage) that have been associated with ASD, in a larger cohort of subjects with well-defined ASD.
Methods:
This study utilizes data from 1,347 individuals (2-17 years old) enrolled in Autism Treatment Network (ATN) Registry. ASD diagnosis was established based on DSM-IV criteria and a standardized battery of assessments, which includes an Autism Diagnostic Observation Schedule (ADOS) and a medical evaluation. The ADM was used by trained physicians to classify subjects as complex or essential. Comparisons between complex versus essential for cognitive level, adaptive behavior, autism severity, quality of life, and behavioral ratings were assessed. Comparisons between the two groups for GI issues, sleep problems, and number of medications were also evaluated.
Results: The sample was homogenous in age and gender. 5.6% of the sample were classified as complex, with complex subjects more likely to have an Autistic Disorder diagnosis vs. Asperger ( p<.021). For the developmental profile, significantly lower scores are seen for complex subjects in cognitive level (p< .025), adaptive behavior (p<.001), quality of life (p<.050). No significant differences in behavioral ratings or ADOS calibrated autism severity scores were found . For the medical comorbidities, complex subjects showed significantly increased physician-documented GI symptoms (p<.003), and are on higher number of medications (p<.001). No significant differences were found in parent-reported sleep problems .
Conclusions:
Using a large ASD sample, this study shows that complex and essential autism have distinct developmental and medical correlates, and thus underlines the importance of looking for dysmorphology, even minor features, in the evaluation of a child with autism. Determining this distinction in autism may have implications in prognosis, identifying medical co-morbidities, directing diagnostic evaluations, recommending treatment interventions, and future research participation.
See more of: Clinical Phenotype
See more of: Symptoms, Diagnosis & Phenotype