["Journal of Applied Research in Intellectual Disabilities, Volume 39, Issue 4, July 2026. ", "\nABSTRACT\n\nBackground and Aims\nDown syndrome (DS) is associated with intellectual disability, with particular difficulties in expressive language and gross motor abilities, and relative strengths in receptive language. Here, we examine how this profile arises over the first five years of life.\n\n\nMethods\nA total of 104 children with DS (6–63 months) participated in a standardised developmental assessment (Mullen Scales of Early Learning; MSEL). Developmental trajectories were analysed cross‐sectionally and validated with a longitudinal subsample.\n\n\nResults\nThe trajectories gradually diverged from typical development, with an uneven pattern across domains. As children with DS get older, their gross motor difficulties persist, their expressive language becomes a relative weakness, and their receptive language becomes an area of emerging relative strength. Longitudinal data revealed limited stability of individual differences except for visual reception.\n\n\nConclusion\nUnderstanding how the DS profile emerges, as well as how stable individual differences are, presents important steps towards tailored support.\n\n"]