Lost in Transition: Delayed Diagnosis of Autism Spectrum Disorder Following Early Migration.

We present the case of a 16-year-old male whose diagnosis of autism spectrum disorder (ASD) was significantly delayed due to the masking effect of early migration. At the age of five, during a critical window for neurodevelopmental identification, he migrated from Portugal to the United Kingdom following an eight-month separation from his primary caregiver. In the years that followed, early autistic features such as language regression, sensory sensitivities, and social withdrawal were attributed to cultural adjustment and second-language acquisition. A comprehensive retrospective developmental assessment in adolescence ultimately revealed that these behaviours were not solely adaptive responses but reflected longstanding features of ASD. This case underscores how environmental transitions during key developmental periods may hinder early identification of neurodevelopmental conditions. It highlights the need for meticulous developmental history-taking and culturally sensitive assessment, particularly when evaluating migrant children whose presentation may be shaped by both intrinsic vulnerabilities and external contextual factors.