This is my last disorder related post. Make sure you've studied because there will be a quiz next post!
Rett Syndrome occurs almost exclusively in girls. It occurs because of a defect in a gene on the X chromosome. Because females have two X's, the extra allows the girl to survive. Males with Rett die very, very early if they survive at all - most are stillborn or miscarried.
Like autism, individuals with Rett can show symptoms by 6 months and are able to be diagnosed by 18 months. The symptoms in social areas are close to autism - lack of verbal ability, avoidance of eye contact and little emotional or social interest in others.
What sets Rett apart from autism is the genetic factor and the physical problems. Most individuals with it cannot walk, have small hands, feet and heads, and may have dystonia. 80% have seizures.
The prognosis of someone with Rett Syndrome is similar to that of a person with severe classical autism. They can be helped through various types of therapy including speech, physical, play and occupational therapy, however, they are unlikely to live on their own or be self-sufficient. They also tend to die at a younger age - around 40 years old - from complications
The next disorder is Childhood Disintegrate Disorder, or CDD. This can be one of the most frightening ASD-related problems because of the late and sudden onset.
Children with CDD develop normally until they reach a point between two and ten years old and then suddenly lose skills. Some parents have reported that their children were aware of the skill loss and scared by it. The skills lost are usually language, self-care, motor and social-related ones, areas of functioning which are normally impaired in autism. Children may also develop seizures, another regular feature of autism.
There's no exact cause known for this disease. Some associate it with a buildup of fatty acids in the brain or a brain infection. The treatments for it are the same as all other pervasive developmental disorders - behaviour therapies to teach the skills which were lost, and medication to control severe seizures and psychotic symptoms.
There are more disorders which are considered closely related to autism, but the five I've detailed in these posts are the most common ones which are considered part of the spectrum. There are variations of all of them - for instance, there is such thing as high-functioning autism which is not related to Asperger's Syndrome - and some people list different symptoms or ways of assessing children for the disorders.
In the end, it's all a pervasive developmental disorder and early treatment is always the key.