An etiologic classification of autism spectrum disorders.

BACKGROUND: Autism spectrum disorders (ASD) represent a common phenotype related to multiple etiologies, such as genetic, brain injury (e.g., prematurity), environmental (e.g., viral, toxic), multiple or unknown causes.

OBJECTIVES: To devise a clinical classification of children diagnosed with ASD according to etiologic workup.

METHODS: Children diagnosed with ASD (n = 436) from two databases were divided into groups of symptomatic cryptogenic or idiopathic, and variables within each database and diagnostic category were compared.

RESULTS: By analyzing the two separate databases, 5.4% of the children were classified as symptomatic, 27% as cryptogenic and 67.75% as idiopathic. Among other findings, the entire symptomatic group demonstrated language delays, but almost none showed evidence for regression. Our results indicate similarities between the idiopathic and cryptogenic subgroups in most of the examined variables, and mutual differences from the symptomatic subgroup. The similarities between the first two subgroups support prior evidence that most perinatal factors and minor physical anomalies do not contribute to the development of core symptoms of autism.

CONCLUSIONS: Differences in gender and clinical and diagnostic features were found when etiology was used to create subtypes of ASD. This classification could have heuristic importance in the search for an autism gene(s).