Autistic Spectrum Disorders 51regression (often accompanied by marked anxiety and loss of bladder
and bowel control), leading to lifelong severe intellectual disability with
pronounced features of autism.
Intense early deprivation
Severe psychosocial deprivation is sometimes followed by persistent fea-
tures of autism. This has been evident from studies of trans-nationally
adopted children who have been deprived in their first year or two of life
of adequate nutrition, physical care, cognitive and linguistic stimulation,
and ordinary social interaction. Though most such children do remarkably
well within a few years of being adopted, a small minority continue to
have social and communicative impairments associated with intense cir-
cumscribed interests, and preoccupations with specific sensations. In early
childhood, the distinction from autism can be difficult. As the children
mature, the clinical picture evolves, with loss of autistic-like features in
around a quarter, leaving social disinhibition and circumscribed intense
interests as the predominant features.
The fragile X syndrome
This is commonly associated with behaviours that bear a superficial re-
semblance to autism. Social avoidance and poor eye contact are common,
but they seem to result from social anxiety rather than social indifference.
Setting aside these features that superficially resemble autism, it remains
controversial whether the fragile X syndrome is any more likely than other
intellectual disability syndromes to result in classical autism.
Deafness
This is often suspected when young children with autism pay no heed to
people speaking to them. A careful history usually establishes that they
have no difficulty hearing sounds that interest them, for example, the
rustle of a crisp packet! Unlike children with autism, deaf children are
typically sociable and keen to communicate, for example, by gesture.
Aetiology and pathogenesis
Roughly 10–15% of individuals with autism have identifiable medical con-
ditions. The likelihood of finding an underlying medical cause is probably
higher when there is severe or profound intellectual disability. A wide
variety of medical disorders have been reported; some may be chance
associations and others may reflect a non-specific increase in the rate of
autistic disorders in any condition that results in intellectual disability. It
is unlikely that the link with intellectual disability is entirely non-specific,
however, since autistic disorders are over-represented in some conditions
that commonly result in intellectual disability, such as tuberous sclerosis
with seizures, but much less commonly seen in others, such as severe
cerebral palsy.