Investigations in Autism Spectrum Disorder & Autism Mimics

Outline of Presentation

  • Genetic investigations
  • Neurometabolic testing
  • Neuroimaging
  • EEG
  • Other tests

Genetic Counselling

  • Multifactorial inheritance
  • RR in siblings - 7% if the affected child is a girl
  • RR in siblings - 4% if the affected child is a boy
  • If a second child has autism, RR of 25–35%
  • 2–3% of families have more than one affected children

Genetic Testing

Yield: 30-40%

  • DNA testing
  • Karyotype
  • Chromosomal Microarray
  • Next Generation Sequencing

DNA Testing

  • Monogenic genetic syndromes(Upto 10%)
    • Fragile X syndrome
    • Tuberous Sclerosis
    • Rett syndrome
  • First tier: Molecular Fragile X screening
  • Next: Direct gene analysis/ MLPA for deletion or duplication
  • PTEN mutations: If macrocephaly

Courtesy: Division of Genetics, AIIMS, New Delhi


  • Upto 5 % (structural rearrangements, aneuploidy)
  • Recurrent abortions
  • For cytogenetically visible deletion

Courtesy: Division of Genetics, AIIMS, New Delhi

Array CGH

  • For copy number variations (submicroscopic deletions, duplications, insetions)
  • Increases the yield to upto 30%

Genet Med 2010

Next Generation Sequencing

  • Single nucleotide variations (SNVs) and very small insertion or deletions
  • Helpful in those with negative array CGH (increases yield by another 7 to10%)
  • Trio studies help in detecting novel candidate genes and de novo mutations

Am J Hum Genet 2013;
Mol Autism 2014

Current Recommendation

  • MLPA/ Karyotype: Recognisable Phenotype
  • Array CGH
  • NGS

Metabolic Screening

Indications (variable combination, yield <1%)

  • Consanguinity
  • Global regression
  • Refractory epilepsy
  • Movement disorder
  • Skin rashes
  • Focal neurological deficits
  • Abnormal head size
  • Lethargy
  • Cyclical vomiting
  • Multiorgan dysfunction
  • Abnormal odour of bodyfluids
  • Dysmorphism

DMCN 2016

Tests Recommended

  • Tailored to individual cases
  •  Serum NH3
  •  Arterial lactate
  •  Urinary aminoacidogram
  •  Blood TMS
  •  Urine GCMS
  •  Urine MPS screen
  •  CSF sugar/lactate/neurotransmitters

DMCN 2013


  • Focal neurological signs
  • Dysmorphic features
  • Neurocutaneous stigmata
  • Abnormal head size (small/large)
  • MRS: Metabolic disorders

AAP 2012

Tuberous Sclerosis

MRS: Cerebral Creatine Deficiency

Role of EEG

  • Clinical seizures
  • Unexplained encephalopathy or behavioral changes
  • Cognitive Decline

AAP 2012



Role of Other Tests

  • Blood heavy metals (particularly in those with pica, serum lead levels)
  • Serum Iron studies can be done in all

Not recommended

  • Food allergy tests
  • Hair mineral analysis
  • Immunologic investigation
  • Assay of vitamin B6 and magnesium levels
  •  Investigations to identify yeast over-growth in the gut

AAP 2012

Autism Mimics

  • ESES: LKS and CSWS
  • Autoimmune encephalitis: NMDAR
  • Paraneoplastic
  • Drugs induced behavioral problems


  • Activation or potentiation of epileptiform discharges in sleep
  • (Near)-continuous, bilateral, or occasionally lateralized slow spikes and waves
  • Occurrence “during a significant proportion” of the non-REM sleep with a threshold ranging from 25% to 85%
  • Original definition suggested >85%
    • This criteria not required by ILAE
  • Awake
    • Most frequent locations of epileptiform discharges are
      • Frontotemporal
      • Centrotemporal
    • In some cases, focal and generalized spike-wave complexes partially overlap
  • Sleep
    • Spiking becomes more frequent and ultimately generalized
    • Frequently with a frontal or central maximum

ESES vs Autistic Regression

Autoimmune Encephalitis

  • Anti NMDA receptor and Anti GAD encephalitis
  • Expressive dysphasia and mutism are common clinical features in children and adults
  • Result of NMDAR hypofunction
  • A prodromal loss of social and communication skills can typify that of an autistic regression, particularly when presenting under age of 3 yrs
  • Role of immunotherapy

Other Mimics (Case Reports)

  • Paraneoplastic: Associated with ALPS
  • Drug induced behavioral problems: associated with levetiracetam


  • Yield of genetic testing in ASD is 30-40%
  • Tiered approach is recommended for genetic testing
  • Indication based investigation are recommended
  • Role of EEG: in distinguishing autism mimics

Thank You

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