Second edition

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with an IQ of 71, although unable to abstract on proverbs
testing or do simple arithmetic, was nevertheless able to ‘correctly
give the day of the week of any day this century’ (Hurst
and Mulhall 1988). In the past, such patients have been
referred to as ‘idiots savants’ (Treffert 1988), and although
this terminology is unfortunate, it does forcefully convey the
sometimes astounding contrast between the ‘islets’ of superior
functioning and the overall intellectual decrement.
Seizures occur in roughly one-third of patients and,
although these are most common in those with mental retardation,
they may also occur in those of normal intelligence.
Infantile spasms may occur in younger children, whereas in
older children and in adults, simple partial, complex
partial, and grand mal seizures may be seen (Danielsson
et al. 2005; Olsson et al. 1988).
Before leaving this discussion of the clinical features of
autism, it is appropriate to comment on the putative entity
known as Asperger’s syndrome. As noted earlier, in some mild
cases of autism, symptoms may not come to light until the
child enters elementary school and, in very mild cases, recognition
may be delayed until much later. Some authors believe
that these cases represent a separate disorder, called Asperger’s
syndrome; myself and others, however, conceive of such
patients as merely constituting the very ‘high-functioning’
end of the spectrum of clinical severity of autism.
Course
The overall outcome is strongly influenced by whether or not
there is an associated mental retardation and, if so, its severity.
With regard to autistic symptoms, there is typically some
gradual improvement by adult years, and, from a prognostic
point of view, the course during middle childhood is particularly
important: those who attain some language and some
social skills around this time have a much more favorable
outcome than those who do not. No matter how great the
spontaneous recovery, however, residual symptoms, such as
aprosodia, social awkwardness, and a reduced awareness of
social conventions, remain in adult years (Rumsey et al.
1985).
Etiology
Etiologic theories regarding autism have changed radically
over the past few decades. This disorder was once believed to
result from faulty child rearing by cold and distant parents.
This theory has now been soundly discredited, and current
research focuses primarily on genetics and neuropathology.
Family studies strongly support a genetic basis. As
noted earlier, the lifetime prevalence is about 0.05 percent;
however, the concordance among monozygotic twins is
over 60 percent (Bailey et al. 1995; Folstein and Rutter
1977). Genetic heterogeneity is almost assured, and linkage
studies have identified loci on various chromosomes,
including chromosomes 2, 3, 7, 11, 15, 19, and X.
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Although MRI studies overall have not been conclusive,
with numerous contradictory results and failures of
replication, two findings appear fairly solid, namely
vermal hypoplasia and a degree of macroencephaly.
Neuropathologic studies (as recently reviewed by Palmen
et al. in 2004), although likewise not conclusive, do suggest
cerebral cortical dysgenesis, abnormalities of neuronal cell
packing and size within the limbic cortex, and a loss of
Purkinje cells within the cerebellum.
It is unclear what role environmental factors play in the
etiology of autism. Recent concerns regarding an etiologic
role of the measles/mumps/rubella vaccine appear
unfounded (Madsen et al. 2002).
Although the etiology of the vast majority of cases of
autism thus remains unclear, it does appear that in a small
minority, perhaps 10 percent, autism occurs secondary to
certain other well-described disorders (Kielinen et al. 2004;
Ritvo et al. 1990), including tuberous sclerosis (Alsen et al.
1994; Lawlor and Maurer 1987), the fragile X syndrome
(Wisniewski et al. 1985c), Rett’s syndrome (Percy et al.
1990), Down’s syndrome (Lund and Munk-Jorgensen
1988), velocardiofacial syndrome (Fine et al. 2005), and
the congenital rubella syndrome (Chess et al. 1978).
Differential diagnosis
As noted, mental retardation is seen in association with
autism in about three-quarters of cases, and hence autism
with mental retardation must be distinguished from
mental retardation of other causes. At times this may be
difficult, given that many patients with mental retardation
of other causes will display repetitive, stereotyped behaviors,
which at times may be similar to the ‘fascinations’ and
stereotypies seen in autism. A cardinal differential feature,
however, is the patient’s social relatedness: upon
approaching a child with mental retardation of other
causes, one may be greeted by a smile and an expectant
posture; by contrast, the child with autism may show no
more interest in the approaching physician than might be
evinced for a machine.
Developmental dysphasia, especially when both expressive
and receptive components are present, may be confused
with autism; however, here again the quality of the
patient’s social relatedness enables a differentiation. The
child with developmental dysphasia, although unable to
communicate verbally, will still, by gesture, tone of voice,
and facial expression, clearly desire social contact, in stark
contrast to the child with autism.
Schizophrenia may enter the differential, especially in
cases characterized by significant inaccessibility and bizarre
stereotypies. Here the age of onset is helpful. As noted
earlier, most cases of autism become obvious by the age of
3 years; by contrast, schizophrenia only very rarely has an
onset before the age of 8 years. Furthermore, in schizophrenia
one finds hallucinations and delusions, symptoms
that are absent in autism.