Martínez Castilla, PastoraCampos, RuthNieto, Carmen2025-10-242025-10-242025-03-27Martínez-Castilla, P., Campos, R., & Nieto, C. (2025). Developmental trajectory of a toddler with PACS1 syndrome: a longitudinal descriptive case study. International Journal of Developmental Disabilities, 1–12. https://doi.org/10.1080/20473869.2025.24832742047-3869https://doi.org/10.1080/20473869.2025.2483274https://hdl.handle.net/20.500.14468/30597This is the Accepted Manuscript of an article published by Taylor & Francis in "International Journal of Developmental Disabilities, 27 marzo 2025, available online: https://doi.org/10.1080/20473869.2025.2483274Este es el manuscrito aceptado de un artículo publicado por Taylor & Francis en "International Journal of Developmental Disabilities" 27 marzo 2025, disponible en línea: https://doi.org/10.1080/20473869.2025.2483274Financiación: This study received support from project PID2020-117087GB-I00, financed by the Spanish Ministry of Science and Innovation. MICIUObjectives PACS1 syndrome is a rare genetic neurodevelopmental disorder first described in 2012. Despite its severe impact on both affected individuals and their families, to date, there have been no detailed characterizations of the developmental trajectory of children with PACS1 syndrome. Our work aimed to fill this gap. It also sought to raise awareness of this syndrome. Methods A 24-month-old boy with PACS1 syndrome was longitudinally assessed every 6 months until 48 months of age. His cognitive, motor, linguistic and socio-communicative development, as well as his adaptative behaviour and sensory profile, were assessed using different tools. At 51 months, symptoms compatible with Autism Spectrum Disorder (ASD) were also explored. Results Delays were observed in all the areas assessed but no regression was noticed. Strong difficulties were observed in communication and language. The most notable developmental progression was seen in socialization. Yet, symptomatology of ASD was also observed. Conclusions Consistent results were obtained through the evaluation tools used in the study, but slight differences were also noticed, highlighting the need for a comprehensive battery of different assessment methods. Raise in linguistic development was concurrent to an intervention aimed at promoting parents’ sensitive response to their child’s behaviour.eninfo:eu-repo/semantics/openAccess61 PsicologíaartículoACS1 syndromedevelopmental trajectorylongitudinal case studylanguage difficultiesevaluation tools