Delayed diagnosis of congenital duodenal obstruction in early adolescence in a patient with Down syndrome and autism spectrum disorder

Congenital duodenal obstruction (CDO) is a recognised anomaly frequently associated with Down syndrome (DS). While complete obstruction is typically diagnosed in the neonatal period, incomplete obstruction may present with milder, non-specific symptoms, often delaying diagnosis.We report a boy in early adolescence with DS and autism spectrum disorder (ASD) in whom CDO was diagnosed in adolescence. Since early childhood, his eating behaviour was restricted to finely chopped foods, initially interpreted as a behavioural feature related to DS and ASD. This likely masked gastrointestinal symptoms and contributed to the delayed recognition of CDO. It is also possible that subclinical duodenal obstruction became symptomatic as food intake increased during puberty.This case highlights the importance of considering incomplete CDO in children with DS, especially those with ASD, when persistent feeding difficulties are present—particularly if attributed solely to developmental or sensory issues.