Definition

 

​A pervasive neurodevelopmental disorder characterised by abnormal or impaired development in:

1. Social interaction

2. Communication

3. Restricted, repetitive behaviours

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ICD-10 F84.0 -- Childhood autism requires symptoms before age 3, affecting at least:

• Reciprocal social interaction

• Communication

• Repetitive behaviours or stereotypical interests

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Epidemiology

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• ​Prevalence: ~1 in 36 children

• Male:Female ratio = 4:1 (females often underdiagnosed)

• Onset: Symptoms typically before age 3

• Comorbidities: ADHD, intellectual disability, anxiety, seizures, epilepsy

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✅ High Yield Associations

• Fragile X = most common inherited cause of autism

• Tuberous sclerosis, Rett syndrome also associated

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Pathophysiology

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• Genetics

  • CNVs (e.g. 16p11.2)​

  • Mutations in CHD8, SHANK3. FMR1

• ​Neuroanatomy

  • Increased total brain volume (especially frontal lobes, amygdala)​

  • Macrocephaly in infancy

• Neurofunction​

  • Decreased activity in fusiform face area​

  • Mirror neurone system dysfunction

• Neurotransmitters

  • Abnormal ​GABA and  glutamate

  • Increased serotonin synthesis

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✅ High yield Exam Prep

• Mirror neuron dysfunction --> impaired social learning and empathy

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Clinical Features​

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Core features (per ICD-10):

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A. Impairment in social interaction

• Poor eye contact

• Lack of joint attention or emotional reciprocity

• Difficulty form age-appropriate peer relationships

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B. Impairment in communication

• Delayed or absent spoken language

• No interest in conversation

• Echolalia or stereotyped speech

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C. Restricted, repetitive behaviours or interests

• Stereotyped movements (e.g. hand flapping, spinning)

• Insistence on routines

• Highly fixated interests

• Hyper- or hypo-reactivity to sensory input

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+ Additional Features

• Developmental regression (~25% lose previously acquired skills)

• Motor clumsiness

• Gastrointestinal symptoms (constipation common)

• Sleep disturbances

• Aggression or irritability

• Savant syndrome (rare; e.g. perfect pitch, calendar calculation) 

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✅ High yield Exam Clue

• Child with normal development --> sudden language/social regression before age 3

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Diagnosis --> Clinical diagnosis based on ICD-10​

 

ICD-10 criteria for F84.0:

• Onset before age 3

• Abnormalities in at least three areas:

  • Reciprocal social interaction​

  • Communication

  • Repetitive behaviours or interests

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Investigations --> To rule out differentials​

 

Bedside:

• Full developmental history

• Behavioural observation (ADOS)

• Parent or carer collateral history

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Bloods:

• Genetic testing (microarray, Fragile X)

• Thyroid function

• Lead levels

• Metabolic screen - if regression or dysmorphism

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Imaging:

• MRI brain only if: focal signs, seizures, regression

• EEG: if seizures or developmental regression without cause

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Management --> Based on biopsychosocial model​​

 

Biological -- to manage associated symptoms​

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• Aggression, irritability --> risperidone, aripiprazole (in children >5 years)​​

• Hyperactivity, impulsivity --> If comorbid ADHD: stimulants (e.g. methylphenidate) or non-stimulants (atomoxetine, guanfacine)

• Anxiety, repetitive behaviours --> SSRIs (e.g. sertraline, fluoxetine)

• Sleep disturbances --> melatonin (first-line), sleep hygiene interventions

• Epilepsy --> antiepileptics (e.g. levetiracetam, valproate)

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Psychological -- focuses on managing communication, social, emotional, and adaptive skills

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• Applied Behaviour Analysis (ABA) --> structured reinforcement learning

• Speech and Language Therapy (SALT) --> for delayed expressive/receptive language, supports non-verbal communication

• Occupational Therapy (OT) --> helps with motor co-ordination and sensory processing difficulties

• Social skills training --> teaches appropriate play, conversion, and peer interaction

• Cognitive Behavioural Therapy (CBT) --> adapted for children with ASD and anxiety or depression

• Parent training programmes --> TEACCH, EarlyBird (UK): teach parents how to support structured, low-stress environments

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Social -- to address the context of the child's life: school, home, family, community

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Educational

• Education Health Care Plan (EHCP) --> document ensuring tailored support in schools

• Special Educational Needs and Disability (SEND) support --> adjustment in mainstream education

• 1:1 teaching assistants --> to improve engagement and inclusion

• Visual schedules and structured environments --> to reduce anxiety and behavioural outbursts

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Family support

• Respite care --> support for family caregivers

• Parent support groups

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Community and safeguarding

• Early help services

• Safeguarding review

• Multi-agency meetings

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Differential Diagnoses

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• Intellectual disability​​

• Selective mutism -- speaks at home but silent at school, normal social interest

• Social communication disorder -- no restricted or repetitive behaviour

• Hearing impairment -- can mimic speech/language delay

• Childhood-onset schizophrenia -- later onset (>7 years), hallucinations and delusions present

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Prognosis

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​Good prognostic indicator​​:

• Early intervention

• Language by age 5

• Higher IQ

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Poor prognostic indicator:

• Seizures

• Intellectual disability

• Regression