Atypical autism: what is it and what subgroups of this disorder exist?

We explain this diagnostic category used in the ICD-10 manual for rare cases of autism.

Diagnostic classifications categorize autism spectrum disorders in different ways. Thus, the DSM-5 eliminates the distinction between Kanner's or classic autism, Asperger's syndrome, Rett syndrome and childhood disintegrative disorder present in the fourth edition of the manual, while the ICD-10 includes the diagnosis of autism in the fourth edition of the manual. ICD-10 includes the diagnosis of "atypical autism"..

In this article we will explain the basic characteristics of this variant of autistic disorder. The diagnostic category is primarily used to describe forms of autism in which the symptoms are mild, uncommon or simply not present in all areasor the age of onset does not correspond to the classic one.

Autism spectrum disorders

The autism spectrum disorders are characterized by deficits in communication and social interaction and alterations in behavioral patterns; in particular, repetitive behaviors and restricted interests are often present.In particular, repetitive behaviors and restricted interests are often present. Intellectual functional diversity, developmental delays and sensory problems are also common.

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which is used as a reference by many clinical psychologists but has received a great deal of criticism, redefined the pervasive developmental disorders described in DSM-IV into a single category: Pervasive Developmental Disorder (PDD). a single category: Autism Spectrum Disorder (ASD)..

Both the DSM-IV and the tenth edition of the International Classification of Diseases (ICD-10) divide autism spectrum disorders or pervasive developmental disorders into different diagnoses: infantile autism or autistic disorder, Asperger's and Rett syndromes and childhood disintegrative disorder.

Both classifications also include an extra category; in the case of DSM-IV this is the "Pervasive Developmental Disorder Not Otherwise Specified" catch-all, which broadly corresponds to the diagnosis of "atypical autism" described in ICD-10.. Let's see what this disorder consists of.

What is atypical autism?

ICD-10 defines atypical autism as a pervasive developmental disorder that does not meet the diagnostic criteria for autism. does not meet the diagnostic criteria for autism.This includes cases in which symptoms and deficits manifest themselves after the age of 3 years or do not occur in the three classic areas of autism: social interaction, communication and restricted, repetitive or stereotyped behavior.

According to this manual, atypical autism appears mainly in individuals with severe intellectual deficits whose low level of functioning prevents them from certain behaviors, as well as in others with severe receptive language disorders. As we will see below, research suggests that these cases can be classified into three distinct subgroups.

There is some debate about the specific characteristics of this form of autism. While some experts describe it as a variant of some experts describe it as a mild variant of classical autism, others of classic autism, others consider that its clinical features and the relationship with other disorders make atypical autism worthy of consideration as a distinct disorder.

Generally speaking, it seems that studies indicate that the average severity of atypical autism cases would be between that of classic autism and Asperger syndrome, which is associated with better social and cognitive functioning. However, given its diagnostic characteristics, atypical autism is an entity composed of very diverse cases.

Subgroups of atypical autism

A study by Walker et al. (2004) published in the Journal of the American Academy of Child & Adolescent Psychiatry compared the level of functioning of children with autistic disorder, Asperger's syndrome and atypical autism.

This research team identified three distinct subgroups that met the diagnostic criteria for classic autism, in addition to finding that in general it is a mild variant of classic autism.

1. With limited stereotypies

The most common subgroup of atypical autism, which accounts for more than 50% of cases, is children who meet all the diagnostic criteria for autistic disorder but present with reduced signs in the area of repetitive behaviors.. This means that the social deficits are much more significant than the stereotypies and restriction of interests.

2. Incomplete autism criteria

According to this research 25% of people with atypical autism present symptoms and signs in the three relevant areas. symptoms and signs in the three areas relevant for diagnosis (communication, interaction and stereotypic (communication, interaction and stereotyped behaviors), although they are not sufficiently marked to meet the criteria. This subgroup would include many cases of autism with severe intellectual deficit.

3. High-functioning

The third set of cases has similarities to Asperger's syndromeis characterized by relatively normal language functioning, but this diagnosis cannot be made because there is a delay in linguistic development and/or relevant cognitive deficits. The proportion of this subtype is also about 25%.