It is believed that one of the first documented references to a case of autism was made by Jean Itard (1774-1838), a French physician working at the French National Institute of the Deaf.
In 1800 a boy of approximately 12-years-old who had spent the majority of his childhood in the woods was brought to the Institute. The boy was named Victor of Aveyron and although he could hear he made no direct communication and was very self-absorbed. Recently, autism expert Uta Frith, declared she believes Victor displayed signs of autism.
Victor of Aveyron was, probably, the first documented case of Autism in history
The history has been dramatized in the movie The Wild Child
The history of Victor of Aveyron dramatized in the movie “The Wild Child”
Andreia on Autism 
I find historic attributions of autism extremely problematic, although they usually name famous scientists and have a somewhat positive note to it.
This case though has so many unknown factors in it, as much on the historic of the child before it was found, the conditions of its “diagnosis” and treatment, qualification of doctors and those reporting the case…. I don’t know how this can be reliably seen as an insight of occurrence of autism in history. Mind you, I am not saying there wasn’t any but the circumstances of this child seem to be so odd, that just concluding it from the little we know is rather unscientific in my eyes.
I agree with you that the history of this child has too many unknown variables involved. Although, from the facts that we know about this child he seemed to have several of the characteristics that are now attributed to children with autism spectrum disorder. Even though we can not ascertain from a scientific point of view that this child had autism, it is still of interest for the history of autism. That was the objective of the post, to provide some background on the history of autism and not a scientific account.
I believe it was a case of Autism. And there were probably many more who were killed or so neglected they died.