The Diagnostic and Statistical Manual of
Mental Disorders, 1994
299.00 Autistic Disorder
Differential Diagnosis
Periods of developmental
regression may be observed in normal
development, but these are neither as severe
or as prolonged as in Autistic Disorder.
Autistic Disorder must be differentiated from
other Pervasive Developmental Disorders.
Rett’s Disorder differs from
Autistic Disorder in its characteristic sex
ratio and pattern of deficits. Rett’s
Disorder has been diagnosed only in females,
whereas Autistic Disorder occurs much more
frequently in males. In Rett’s Disorder,
there is a characteristic pattern of head
growth deceleration, loss of previously
acquired purposeful hand skills, and the
appearance of poorly coordinated gait or
trunk movements. Particularly during the
preschool years, individuals with Rett’s
Disorder may exhibit difficulties in social
interaction similar to those observed in
Autistic Disorder, but these tend to be
transient. Autistic Disorder differs from Childhood
Disintegrative Disorder, which has a
distinctive pattern of developmental
regression following at least 2 years of
normal development. In Autistic Disorder,
developmental abnormalities are usually noted
within the first year of life. When
information on early development is
unavailable or when it is not possible to
document the required period of normal
development, the diagnosis of Autistic
Disorder should be made. Asperger’s
Disorder can be distinguished from
Autistic Disorder by the lack of delay in
language development. Asperger’s
Disorder is not diagnosed if criteria are met
for Autistic Disorder.