Autism has a genetic component, so people can be born with it. Others are born with a susceptibility to autism that is probably triggered by an environmental factor. So, there are newborns with autism. Usually, autism is not diagnosed until age 2 or 3, but some cases are diagnosed earlier, and some are not identified until much later.
Her youngest son has Down's Syndrome, but she has a nephew with autism.
An Autistic is a person with Autism.
A person does not 'develop' autism - a person is born autistic.
A person does not 'develop' autism - a person is born autistic.
A person does not develop autism. Autism is a neurological difference, as such it starts within the womb during the second trimester when the brain is being formed.
Someone who is born on the autism spectrum/has autism spectrum disorder/is autistic. Often used in an offensive manner towards autistic people.
The eyes of a person with autism look the same as the eyes of other people.
A person does not develop autism, autism is not something that occurs to neurotypical people, in the same way that a white person doesn't develop into another race. A person is born autistic, their brains form in the womb.
A teenager doesn't develop autism - a person is autistic from birth.
Autism can be inherited from parents with genes for autism. Autism can also be the result of the spontaneous mutation of a gene. It is suspected that a person with the genes for autism might need an environmental factor (in the womb or shortly after birth) to trigger the development of autism.
A person does not 'have' autism, a person is Autistic. Autism is a neurological variation that results from genetics, there's nothing conclusive to say that environmental factors contribute to this.
The youngest person would constantly be changing as it would be the newest born person.