Clinicopathological Stratification of Idiopathic Autism and Autism with 15q11.2-q13 Duplications

Postmortem studies of brains of individuals with idiopathic autism and 15q11.2–q13 duplications autism (dup(15)) identify a cluster of neuropathological features differentiating these cohorts. They show a need for both reclassification of autism according to etiology, clinical presentation and neuropathology, and a commonality of clinical and neuropathological traits justifying autism diagnosis. The features differentiating these cohorts include: (a) maternal origin in patients with dup(15); (b) autism in 78% of subjects; (c) more severe clinical phenotypes, with intellectual deficit (100%), early-onset of severe or intractable seizures in 78% of subjects, and increased prevalence (up to 67%) of sudden unexplained death; (d) high prevalence of microcephaly, with mean brain weight 300g less than in idiopathic autism; (e) several-fold increase in the number of developmental abnormalities, including defects of migration and dysplastic changes, especially numerous in the hippocampal formation; and (f) significant increase in the intraneuronal amyloid load, reflecting enhanced amyloid-β precursor protein processing with α-secretase.