This article focuses on the consequences of having FraX-E, the rare but well recognised variant of fragile X syndrome. The authors provide some background on the condition and report on recent research and evidence. Three case reports are outlined and the specific behavioural aspects of the syndrome are considered. The authors argue that it is important that the behavioural phenotype for FraX-E is clearly identified and defined in order to give those with the condition relevant psychological and educational support in the future.