Autism Spectrum Disorder Differential Diagnoses

Updated: Nov 27, 2018
  • Author: James Robert Brasic, MD, MPH; Chief Editor: Caroly Pataki, MD  more...
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Diagnostic Considerations

A major public health problem in the care of children with autism spectrum disorder and other pervasive developmental disorders is the inconsistent diagnosis of autism. Criteria for the diagnosis of autism are included in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, and the International Classification of Diseases, Ninth Revision, Clinical Modification, Fourth Edition (ICD-9-CM) . [4, 101]

Although the criteria for autism and other pervasive developmental disorders differ between the DSM-V and the ICD-9-CM, they are both widely accepted and are used around the world by clinicians and researchers.

A discussion of the differences in the criteria for autism and related conditions in the DSM-V, the ICD-9-CM, and other nomenclatures is beyond the scope of this article. The key point for pediatricians and other clinicians is that the criteria for autism and related conditions in the DSM-V and the ICD-9-CM are presented in an outline form without a discussion of the terms used.

The DSM-V and the ICD-9-CM are poor textbooks of child development and child psychopathology; they do not fully describe the concepts incorporated in the criteria for autism and related conditions. Therefore, an inexperienced clinician is likely to incorrectly apply the criteria for autism and related conditions in the DSM-V and the ICD-9-CM.

The diagnosis of Autistic Disorder in DSM-V has 2 key criteria [4] :

  • Impairments in social communication and social interaction

  • A restricted, repetitive range of interests, behaviors, and activities

Diagnostic error and clinician experience

To administer tools for the diagnosis of autism and related conditions in a reliable and valid manner requires extensive training and experience. Therefore, unless they have wide experience with children with autism and understand the concepts implicit in the diagnostic criteria and rating scales, pediatricians and other clinicians are advised to refer patients with possible autism to experienced clinicians for definitive diagnostic evaluations.

Delayed diagnosis of autistic disorder and related conditions is a serious problem, because early initiation of treatment increases the likelihood of a favorable outcome. Many parents report raising concerns to their pediatricians about the patient's development in the first months and years and being told only that the child will outgrow the problem.

Screening tests

Procedures are available for diagnostic screening by practicing pediatricians, including the Checklist for Autism in Toddlers (CHAT) and its revisions, the Modified CHAT (MCHAT) and the Quantitative CHAT (QCHAT). [90, 91] Some items of the CHAT appear to have strong cultural biases that rule out the direct application of this instrument to populations outside the United Kingdom; however, cross-cultural adaptions of CHAT have been prepared. [102]

However, the 3 items of the CHAT that are highly predictive of the development of autistic disorder (ie, protodeclarative pointing, gaze monitoring, pretend play) can be quickly assessed by clinicians during well-baby visits (see Presentation for detailed descriptions of these items). Pediatricians can facilitate early diagnosis of autistic disorder and related conditions by performing a screening procedure at every visit, including well-baby check-ups, school examinations, and immunization appointments.

Assessment of motor and self-care skills in children with autism is recommended to address clumsiness and sensory issues. [103] If a standardized test to assess sensory processing difficulties is warranted, one of the following tools is recommended [104] :

  • Sensory Processing Measure - For children aged 5-12 years

  • Short Sensory Profile - For children aged 37 months to 9 years

  • Infant/Toddler Sensory Profile - For children aged 7-36 months

Cultural considerations

Of note are cultural considerations in the evaluation of a child with possible autism. Cultural and familial differences exist in expectations regarding eye contact, play, social interaction, and pragmatic use of language. When English is not the family’s primary language, professionals should be conscious of finding ways to communicate effectively with the family, including finding professionals and/or translators who speak the primary language. [105]

Other disorders

Other disorders to consider in the differential diagnosis of autism are as follows:

  • 44,XXX karyotype

  • 47 chromosomes

  • (7;20) balanced chromosomal translocation

  • Angelman syndrome

  • Deletion 1p35

  • Duplication of bands 15q11-13

  • Extra bisatellited marker chromosome

  • Habit disorder

  • Infantile hydrocephalus

  • Interstitial deletion of (17)(p11.2)

  • Inv Dup (15)(pter->q13)

  • Language disorder - Mixed, phonologic, receptive, or stuttering

  • Long Y chromosome

  • Minamata disease

  • Moebius syndrome

  • Nonketotic hyperglycinemia (NKH)

  • Partial 6p trisomy

  • Epilepsy

  • Infantile spasms

  • Tourette disorder

  • Trisomy 22

Children with lead poisoning may demonstrate neurobehavioral changes. Constipation, abdominal pain, and/or anorexia are common. Lead poisoning in children at risk should be ruled out through appropriate testing.

Age of onset

Autistic disorder manifests in early childhood. By contemporary criteria, the absence of abnormalities in the first 30 months of life rules out autistic disorder. For information about individuals with later onset of symptoms consistent with autistic disorder, see the following articles:

Many parents report normal development in their child until age 2 years before noticing the deficits in social and communicative skills.

Differential Diagnoses