Autism Spectrum Disorder (Regressive Autism, Child Disintegrative Disorder)

Epidemiology

Autism spectrum disorder becoming increasingly prevalent, and its prevalence is reported to be 1 in 68. Childhood disintegrative disorder is a rare disease, with only 1.7 in 100,000 cases, and the prevalence of this disease is estimated to be 1 to 2 in 100,000.

Childhood disintegrative disorder is 4 times more common in boys than girls.

Pathophysiology

There is no clear-cut pathology of the disease, so the causes of childhood disintegrative disorder are still unknown. Regression occurs in children who have achieved normal developmental milestones, and this regression sometimes occurs very rapidly. This condition develops in days or over time and is most commonly seen in the fourth year of life, but there can be variation. Some consider it to be childhood dementia, indicating that the deposition of amyloid in the brain can be the possible cause of the disease, but this needs to be proven.[3][4]

History and Physical

The symptoms of ASD are usually identified by 2 years of age, and one-third of children experience regression of skills at the same time. The symptoms of childhood disintegrative disorder usually start later, at around 4 years of age. In ASD, regression of skills develops around 2 years of age, while in childhood disintegrative disorder, regression is later, more severe, and more global in extent. Children with childhood disintegrative disorder generally have the worst outcome among individuals with ASD. Their cognitive and communication skills are affected. Most children with childhood disintegrative disorder experience a distinct prodrome characterized by bouts of anxiety and terror with no consistent medical, environmental, or psychosocial triggers.

A child affected with childhood disintegrative disorder shows normal development, and they normally develop age-appropriate verbal and nonverbal communication, as well as social relationships, motor, play, and self-care skills as compared to other same-aged children. However, by 2 to 10 years of age, they almost completely lose their acquired skills in 2 of the following 6 functional areas:

• Receptive language skills (comprehension of language: Listening and understanding what is communicated)
• Expressive language skills (being able to produce speech and communicate a message)
• Social skills and self-care skills
• Bowel and bladder control
• Motor skills
• Play skills

Impairment of function also occurs in social interactions and communications.

The 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) Criteria for Childhood Disintegrative Disorder Diagnosis (WHO)

• Normal development up to the age of at least 2 years; the presence of normal age-appropriate milestones are achieved in the areas of communication, social relationships, play, and adaptive behavior at age 2 years or later are required for this diagnosis.
• A definite loss of previously acquired skills at the onset of the disorder. The diagnosis requires a clinically significant loss of skills (and not just a failure to use them in certain situations) in at least 2 of the following areas:
  • Expressive or receptive language
  • Play
  • Social skills or adaptive behavior
  • Bowel or bladder control
  • Motor skills
• Qualitatively abnormal social functioning, manifest in at least 2 of the following areas:
  • Qualitative abnormalities in reciprocal social interaction (of the type defined for autism)
  • Qualitative abnormalities in communication (of the type defined for autism)
  • Restricted, repetitive, and stereotyped patterns of behavior, interests, and activities, including motor stereotypies and mannerisms
  • General loss of interest in objects and the environment
• The disorder is not attributable to the other varieties of the pervasive developmental disorder acquired aphasia with epilepsy, elective mutism, schizophrenia, Rett syndrome

Evaluation

Children diagnosed with childhood disintegrative disorder rarely reveal an underlying neurological or medical cause. Complete medical and neurological examinations are done and tests to exclude reversible  causes of the condition:

• Complete blood count
• Urea and electrolytes/glucose
• Liver function test
• Thyroid function test
• Heavy metal levels
• HIV testing
• Urine screening for aminoaciduria
• Neuroimaging studies (MRI or CT scan)
• Electroencephalogram (EEG)

These tests are usually done during initial assessment in secondary care. Electroencephalogram (EEG) and neuroimaging studies are done to exclude the alternative diagnosis.