Schizophrenia is considered an heterogenous disorder. Different etiopathological mechanisms can attribute to a similar clinical picture as described in DSM-criteria. We present a case of a young man diagnosed on different occasions with DSM-III-R schizophrenia and mild mental retardation. Clinical examination revealed signs and symptoms most compatible the diagnosis of Lujan-Fryns syndrome, an X-linked mental retardation with `Marfanoid features' and frequently associated with psy- chotic or other psychiatric symptoms. In all patients with symptoms of schizophrenia and mental retardation the Lujan-Fryns syndrome should be considered in the differ- ential diagnosis.