When I was diagnosed at the age of two, the doctors seemed to be unusually taken with me. I presented a unique case for them - I tested incredibly high on the IQ test administered to me and most importantly was (and still am) female. In 1990, it was largely assumed autism was exclusively present in boys who bordered on or were mentally retarded. I can only assume this was the reason they wanted to hospitalize me for a month for further study - smart autistic girls apparently are a rarity.
For the record, my mother refused to let them do that. I cannot be more grateful for that decision - I already begun to bond with my mother and would have missed her.
In fact, it's still considered a rarity. Boys and men are four times more likely to receive an autism diagnoses than their female counterparts. It just seems to be easier to notice when a boy is antisocial and withdrawn with specialized interests than when a girl is. Whether that's due to neurological differences or general societal expectation, it's created the image of autism looking like a little white boy.