|
|
||
Introduction
Autism and Rett Syndrome
are devastating, lifelong neurological disorders that are classified as pervasive
developmental
disorders (sometimes abbreviated PDD). Autism and Rett Syndrome are characterized
clinically by severe, pervasive
impairment in communication skills and in reciprocal social interaction skills.
Stereotyped behavior and interests are
typical. In many cases, autism and Rett Syndrome are accompanied by mental retardation
as well as seizures. These
disorders cause significant hardships for the affected children and adults,
as well as their families, schools and
communities.
Today, the diagnosis of
autism and related pervasive developmental disorders such as Asperger's Syndrome
is based
upon clinical criteria. There are no known biological causes. There are very
few proven neurochemical, genetic,
neuroanatomical, neurophysiological, structural, metabolic, or other molecular
differences between these patients and the
normal population.
Autism: what is known
Autism was first described
in the 1940s by Leo Kanner of Johns Hopkins. It is characterized by a triad
of deficits: (1) an
individual's failure to have normal reciprocal social interactions, (2) impaired
language or communication skills, and (3)
restricted, stereotyped patterns of interests and activities. Some autistic
children appear to develop normally but then
undergo a period of regression in language skills between 18 and 24 months of
age. 75% of autistic individuals have
mental retardation. The prevalence of autism has been estimated to be from 1:500
to 1:2,000 individuals.
The cause of autism is unknown,
but the disorder is clearly genetic. The concordance between monozygotic twins
is 60%,
and >90% if coaffected twins are defined as having classically defined autism
or more generalized impairments in social
skills, language, and cognition. Most genetic linkage studies have not resulted
in the identification of genes that are
significantly associated with autism, although the long arm of chromosome 15
has been implicated.
Some autism web links:
National Alliance for Autism Research (NAAR)
National Autistic Society (NAS)(includes many autism-related links)
Rett Syndrome: Background
Rett Syndrome affects girls
almost exclusively. The diagnosis is based upon clinical criteria including
deceleration of head
growth during development, loss of purposeful hand movements, development of
severely impaired language, and
sterotyped movements. Twin studies suggest that the cause is genetic, and linkage
studies implicated the X chromosome.
In October 1999, Huda Zoghbi
and colleagues discovered
that mutations in the gene encoding methyl-CpG binding
protein 2 (MeCP2) cause some cases of Rett Syndrome. MeCP2 is a transcriptional
repressor, and mutations in this gene could allow many other genes to be inappropriately
overexpressed.
Some Rett Syndrome web links:
International Rett Syndrome Foundation (IRSF)
The Great Mississippi River Race for Rett Syndrome
Updated 1-21-10