Differential Diagnosis

An autism diagnosis is based on specific criteria (e.g., from the Diagnostic and Statistical Manual, Fifth Edition [DSM-5]) and a health care provider experienced in diagnosing and treating autism is usually needed to make the actual diagnosis. Newer definitions of autism include a wider spectrum (autism spectrum disorders).

A diagnosis of autism often involves routine developmental examinations and evaluations, as well as further testing—including specific screening tools for autism. Other developmental disorders that can produce symptoms similar to autism include the following:

Tests performed to rule out other conditions include the following:

  • Blood tests (to rule out metabolic disorders that affect amino acids and lipids in the blood)
  • Chromosomal analysis (to rule out genetic disorders)
  • Comprehensive hearing test (to rule out deafness as the cause of abnormal language development)
  • Electroencephalogram (EEG; to rule out seizure disorder)
  • Magnetic resonance imaging (MRI scan; to rule out brain disorders)

Asperger's syndrome is no longer considered a distinct condition and is now classified as an autism spectrum disorder. Autism spectrum disorders are more common in boys, usually develop after the age of 3, and may not require lifelong care. Children with autism spectrum disorders have narrow interests, repetitive routines, and are at increased risk for developing depression and anxiety. Symptoms include the following:

  • Excellent rote memory (usually)
  • Excellent musical ability (often)
  • Inability to use language to communicate
  • Lack of facial expressions and emotion
  • Limited interests and an intense interest in one or two areas
  • Severely impaired social interaction
  • Undeveloped motor skills

Childhood disintegrative disorder causes marked deterioration of intellectual, social, and language skills around the age of 3 or 4. The disorder is associated with seizures and is more common in boys. Patients with the condition usually require lifelong care. Childhood disintegrative disorder causes loss of the following:

  • Bowel and bladder control
  • Language (i.e., ability to communicate and understand others)
  • Motor skills
  • Social skills (e.g., ability to play, develop peer relationships)

Rett disorder is a progressive neurological disorder that occurs only in girls. Symptoms of the disorder usually develop between 6 and 18 months of age. It is characterized by the following:

  • Abnormal gait
  • Inability to control hand movements
  • Inability to express feelings
  • Reduced brain size and weight (microcephaly)
  • Reduced muscle tone (hypotonia)
  • Seizures

Patients also may experience constipation, breathing difficulties, weakness of the extremities, and cognitive regression. There is no cure for Rett disorder, but symptoms usually can be managed with appropriate treatment.

Pervasive developmental disorder-not otherwise specified (PDD-NOS) is also now characterized as an autism spectrum disorder involving delayed development of social and communication skills. It usually develops between 2 and 12 years of age. Individual attention and medication to manage behavioral problems can be beneficial. Symptoms include:

  • Abnormal play behavior
  • Desire for sameness in their environment
  • Difficulty using and understanding language
  • Impaired ability to relate to people, objects, and events
  • Repetitive movement and behavior
  • Self-injury
  • Unusual mannerisms

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 29 Feb 2000

Last Modified: 01 Sep 2015