American Society of Human Genetics 2017

People who have a mutation linked to autism plus a second genetic glitch tend to have more severe symptoms than those with the mutation alone.

Mutations in the gene PTEN that are tied to autism may be less harmful than those linked to a syndrome characterized by benign tumors.

More than 5 percent of mutations thought to have arisen spontaneously in a child with autism may in fact be inherited.

Rare autism mutations linked to low intelligence

People with autism who have rare, damaging mutations tend to have low scores on intelligence tests.

People with attention deficit hyperactivity disorder may carry certain rare, harmful mutations in many of the same genes as people with autism.