We report a young patient with phenotypic, cognitive and behavioural features consistent with a diagnosis of Lujan-Fryns syndrome. He exhibited a severe eating disorder with food refusal and psychogenic loss of appetite, which led to a serious state of malnutrition. Behavioural difficulties including shyness, hyperactivity and emotional instability are present in almost 80% of the described patients with Lujan-Fryns syndrome but eating disorders have not been previously reported in this condition. A review of the behavioural problems in Lujan-Fryns syndrome and an approach to their management is discussed.