Differential diagnosis between autism spectrum disorder and other developmental disorders with emphasis on the preschool period

Background Neurodevelopmental disorders are a heterogeneous group of conditions that manifest as delays or deviations in the acquisition of expected developmental milestones and behavioral changes. Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in communication and social interaction and by repetitive and restricted patterns of behavior, interests and activities. The aim of this review is to discuss the clinical features of the differential diagnoses of ASD that are prevalent among preschoolers, focusing on their similarities and disparities. Data sources The international medical literature search was conducted using PubMed and was revised regarding the subject using single and/or combined keywords as follows: differential diagnosis, preschoolers, diagnostic challenge, attention deficit hyperactivity disorder, intellectual disability, high abilities/giftedness, childhood apraxia of speech, social communication disorder, Landau–Kleffner syndrome, stereotyped movement disorder and excessive screen time. Results We describe conditions commonly found in clinical practice, taking ASD as a reference. We addressed converging and divergent aspects of behavior, cognition, communication, language, speech, socialization, and stereotypes for the diagnosis of ASD and other disorders identified as potential differential or comorbid diagnoses. Conclusions The ranking and characterization of symptoms appear to be essential for better understanding the underlying common ground between children with developmental disorders and children with ASD, thus properly diagnosing and directing social, professional, or medication interventions. This detailed discussion adds to the literature since, although ASD differential diagnoses are frequently mentioned and discussed in textbooks and journal articles, they rarely occupy a prominent place as we aimed herein.