122: Autism Spectrum Disorders

Key Points

• Disease Summary:

  • Autism spectrum disorders (ASD) are a heterogeneous group of disorders characterized by impairments in social communication and the presence of restricted interests or repetitive behaviors.

  • With increasing recognition of autism, it may also be diagnosed in adults who have received other diagnoses in the past (e.g. Intellectual Disability).

  • Autism is usually a lifelong condition. However, the range of disability is variable. Some individuals may be able to function in the community with variable levels of supports, whereas others may require more intensive residential based supports.

  • Management of Autism is multidisciplinary and involves addressing the core deficits (communication and restricted/repetitive behaviors) as well as comorbid psychiatric and medical conditions.

• Differential Diagnosis:

  • Autism is often confused with intellectual disability. Although the two conditions often co-occur, intellectual disability is not a core diagnostic feature of autism. Other disorders with features that may be confused with autism include social anxiety/selective mutism, obsessive-compulsive disorder, expressive/receptive language delay, Attention Deficit Hyperactivity Disorder, schizophrenia, acute psychological trauma, and rare epilepsy syndromes leading to speech regression and hearing loss.

• Monogenic Forms:

  • Monogenic forms of autism include both "syndromic" and "non-syndromic" autism. "Syndromic" autism includes disorders associated with congenital malformations, facial dysmorphic features, abnormal head sizes or linear growth, seizures, and hypotonia and/or muscle weakness. Monogenic "non-syndromic" autism is often due to genes that encode neuronal and synaptic proteins; they are typically not associated with other clinical features, except for intellectual disability.

• Family history:

  • Monogenic autism can be inherited in an autosomal dominant, autosomal recessive, and X-linked pattern, but there can be variable expressivity and variable penetrance.

  • Some individuals with autosomal dominant forms of autism have de novo mutations and hence would not have any family history of the condition.

  • Female carriers of X-linked syndromic autism may have mild manifestations of some autistic features such as rigid personality and a strong desire for routines. The empiric recurrence risk of having a second child with autism (ie, having a sibling with autism) in cases where the underlying etiology is unknown is about 3%-5%.

• Environmental factors:

  • Prenatal exposure to specific teratogens can be associated with syndromic autism. Postnatal exposure to lead in young children may also result in autism. Gene-environment interactions may also play a role in the pathogenesis of autism in some individuals.

• Genome Wide Association Studies:

  • These studies have identified numerous chromosomal loci associated with autism. The causative genes at a few of these loci are now known, but the causative genes at many of these loci are still unknown.

• Pharmacogenomics:

  • Considering the genetic heterogeneity in autism, pharmacogenomics are of great interest. However, at the time of writing no specific pharmacogenomically driven intervention strategies are approved.

Diagnostic Criteria and Clinical Characteristics

Clinical Characteristics

Autism spectrum disorders (ASDs) are a heterogeneous group of disorders characterized by impairments in social communication and the presence of restricted interests or repetitive behaviors. Although autistic disorder, Asperger syndrome, and ...