Autism, a neurodevelopmental disorder, is commonly thought to be a genetic disorder and that genetic differences account for problems in early brain development and behavior. We do know there is no single cause for autism. For about 10 percent of children, we can identify a known cause such as Fragile X and chromosome 15 duplications. Researchers have identified several genes that may cause a predisposition to autism in some, but not all, children. Much remains to be learned about genetic factors. Other researchers are attempting to determine if environmental factors, such as toxins and chemicals, play a role in causing autism.