Abstract
Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with rising prevalence, necessitating early diagnosis and intervention. This case report examines the clinical diagnosis approach of ASD in children under two years, emphasizing motor developmental delay, chromosome 19 mutations, prematurity, macrocephaly, and false-negative Modified Checklist for Autism in Toddlers (MCHAT) results. This study identifies gross motor delays as a potential key indicator in the diagnosis of ASD, as all five cases (Patients A, B, C, D, and E) were observed to have such deficits. Two cases (Patients A and B) initially had negative MCHAT results but were later diagnosed with ASD. Patients C and E both had a chromosome 19 abnormality. Patient E had macrocephaly and an amino acid metabolism disorder. ASD atypical behaviors like hand flapping, wringing, and twirling were also noted. Our systematic review validated the key findings presented in this study, unveiling a consistent pattern throughout the existing literature about ASD diagnoses and the associated misconceptions. These cases highlight the significance of early motor delay, genetic factors, and the limitations of MCHAT in early ASD diagnosis. This case report underscores the need for improved screening tools, genetic investigations, and comprehensive assessments to enhance early detection and intervention for ASD. Early identification and personalized interventions hold a promise to improve the outcomes and quality of life for children with autism.