Abstract
An early diagnosis of autism spectrum disorder, leading to a timely enabling intervention, is associated with a better long-term prognosis and allows the early detection of any medical comorbidities that are sometimes found in individuals with autism. It is, therefore, an important challenge to begin the diagnostic procedure of these children as soon as possible. Nowadays, much progress has been made in this respect compared with the past, but considerable work remains. A fundamental role in starting a correct and timely diagnostic procedure is obviously played by the pediatrician. Today, many tools are available for the early screening of autism in the general population, but unfortunately, their real effectiveness has yet to be established. In this narrative review, we address the topic of the early diagnosis of autism spectrum disorder, emphasizing, in particular, those that are now considered the first warning signs. We list a few of the most important signs to consider when a child aged around 18 months presents to a pediatrician, subdivided into three subgroups: social-communication skills; patterns of behavior, interests, or activities; and sensory behaviors and reactivity/temperament. We deal separately with the possible presence of slight motor signs, which can also go unnoticed, but probably they should be considered as very early signs appearing even before social-communication deficits.