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Autism Spectrum Disorder
Published in Ivanka V. Asenova, Brain Lateralization and Developmental Disorders, 2018
Recently, Mottron et al. [87] have proposed the Trigger-Threshold-Target Model to describe the phenotypic, cognitive and genetic heterogeneity of autism. According to the model, upregulated synaptic plasticity due to genetic mutations triggers brain reorganization in individuals with low plasticity threshold, mostly within regions sensitive to cortical reallocations, the multimodal association cortices. Perturbation of the experience-dependent development of cortical organization and behavioral phenotypic consequences are the final results of this plasticity reaction. Differences in the target of brain reorganization, perceptual versus language regions, account for the main autistic subgroups: with and without speech onset delay. Since, in the model, non-syndromic and syndromic autism are considered as the two ends of the ASD, it is suggested that enhanced but normal plasticity may underlie non-syndromic autism, whereas altered synaptic plasticity, triggered by genetic mutation or event, may underlie syndromic autism with intellectual disability and dysmorphism in addition to autism.
Genetics
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
Jane A. Hurst, Richard H. Scott
Males with fragile X typically have moderate learning difficulties. Behavioural difficulties, often leading to a diagnosis of autism, are common. Physical features present in some include relative macrocephaly, a long face, prominent ears, squint, joint laxity, mitral valve prolapse and large testes (Fig. 15.25). Affected females typically have mild learning difficulties. Diagnosis: Southern blotting and/or PCR analysis to identify the causative expansion mutation in the FMR1 gene.Inheritance: X-linked recessive.Natural history: the features of the fragile X syndrome are largely static.Differential diagnosis: chromosome abnormalities.Sotos syndrome.Non-syndromic autism of unknown cause.
Leo Kanner and autism: a 75-year perspective
Published in International Review of Psychiatry, 2018
More than 100 genetic syndromes have been linked to ASD (Betancur, 2011). The number of genetic syndromes associated with ASD reflects its clinical heterogeneity (de la Torre-Ubieta, Won, Stein, & Geschwind, 2016). Overall genetic findings, diagnostic methodology, clinical differences, within-syndrome comparisons, distinctiveness of behavioural phenotypes, and individual developmental trajectories must be considered. Similarities and differences among syndromes and non-syndromic autism must be carefully evaluated by detailed fine grained analysis of the full behavioural phenotype of each syndrome. For those with genetic syndromes and social deficits, the new DSM-5 diagnosis of social (pragmatic) communication disorder might be more appropriate.
Nitric oxide pathway as a plausible therapeutic target in autism spectrum disorders
Published in Expert Opinion on Therapeutic Targets, 2022
Rishab Mehta, Anurag Kuhad, Ranjana Bhandari
Autism is generally characterized into two broad categories, that is, syndromic autism and idiopathic autism. Syndromic autism also known as secondary autism is known to be caused by well-defined cause such as gene mutation like Fragile X syndrome, Timothy syndrome, Angelman syndrome and tuberous sclerosis, and so on [6,16]. The alteration or mutation in a single gene is responsible for 10% of autistic cases. Table 1 represents various syndromes that occur due to certain genetic mutations leading to autism and associated disorders.