Did you know that individuals who have siblings with autism or related pervasive developmental disorders have a greater chance of having the disorder as well? Studies also show that identical twins are more likely to share autistic traits than fraternal twins. These are major indicators that there may be a genetic cause for autistic disorder. Current research says that there may be other factors that contribute to the autism including gene abnormality and gene mutation. The combination of gene mutations might help to explain why there is such a wide spectrum of abilities in individual who have autism or related pervasive developmental disorders. Some cases of autism are quite severe while others are very mild. If the problems are caused by a combination of different genetic abnormalities then we can expect the disorder to manifest itself in a number of ways. Researchers are targeting certain chromosomal regions in order to pinpoint the specific genes that may have a direct link to autistic disorder. As of right now there is no conclusive evidence that all pervasive developmental disorders are caused by genetic mutations.