Key pointsWe have identified a patient with a smaller deletion in the WS critical region and an atypical cognitive and behavioural profile.The patient had SVAS and vesicoureteric reflux with megaureter. He had normal development, with a mild delay in language acquisition.The subject’s cognitive performance was compared to an age matched control group of nine WS subjects with a typical deletion (WSCG) and the results were significantly different for both general intelligence (borderline IQ v mild impairment) and for visuospatial and visuoconstructive abilities (relatively preserved v compromised). His cognitive profile did not show the usual WS cognitive and behavioural pattern. His development differs from both the WSCG and normally developing children.