Autistic spectrum disorder (ASD) is characterised by persistent deficits in the ability to initiate and to sustain reciprocal social interaction and social communication, and by a range of restricted, repetitive and inflexible patterns of behaviour, interests or activities that are clearly atypical or excessive for the individual's age and sociocultural context

Aetiology

• No clear unifying pathological mechanism - combination of environmental, biological, and genetic factors
• M:F ratio about 4:1
  • Suggested link to sex hormones
  • Some have suggested the difference is due to misdiagnosis of girls
• Co-morbidities frequent e.g. depression, anxiety, EDs, Tourettes, OCD, ADHD, learning disabilities

Risk factors

• Rubella in the pregnant mother
• Tuberous sclerosis
• Fragile X syndrome
• Encephalitis
• Untreated PKU
• ASD and gender identity:
  • 8-10% of children and adolescents seen at GID clinics meet the clinical diagnostic criteria for autism (3-4 x more common than in general population)
  • Studies in girls with congenital adrenal hyperplasia showed more traits of ASD than controls and higher levels of gender dysphoria

Pathophysiology

Neuroanatomy of autism

• Frontal lobes, amygdala, and cerebellum appear pathological in autism

Neurochemistry of autism

• Glutamine receptors, GABA and serotonin seem implicated
• GABA has a key role in the regulation of early developmental stages of cell migration, neuronal differentiation and stages of maturation
• Glutamate is an essential exctitatory neurotransmitter which dysregulation can lead to neuronal damage
• Serotonin neurotransmitter system has a critical role in the regulation of crucial steps of neuronal development