The vast majority of autism cases are congenital. Because sufferers are no different from normal children in appearance, the condition is difficult to discover during early infancy. The symptoms become more apparent at the age of 12 to 30 months.
絕大多數的自閉症都是先天的，因外表與正常的孩子無異，在襁褓期不容易發現，在十二個至卅個月之間的嬰幼兒期，症狀較顯著。