IntroductionThe paper discusses the problem of psychiatric treatment of rare diseases and “diagnostic screening” of certain psychic symptoms that affect people with intellectual disabilities. Prader–Willi (PWS) is a genetic syndrome that belongs to a group of rare diseases and is caused by deficiency or loss of function of genes on chromosome 15 inherited from the father. This disease affects both sexes and its main characteristics are: obesity, hyperphagia, mental retardation and hypogonadism. Chronical feeling of insatiable hunger and slow metabolism leads to excessive body weight which is, according to existing date sources and monitoring studies, the primary cause of premature death of patients with PWS. Anxiety, psychomotor agitation, behavioral problems, difficulties with short-term memory, frequent skin injury in the form of wounds and bruises are the symptoms of this disease that hinder diagnosis and treatment. Research suggests that patients with PWS have unusual reactions to the standard drug dosages, specifically anxiolytics.AimWe shall present a multidisciplinary approach of pharmacological and psychotherapeutic treatment of a 16-year-old female patient with PWS.ResultThis patient responded well to a small dosage of quetiapine, at the same time monitoring other physical parametres. Pharmacotherapy, combined with psychotherapy, along with providing counseling and support for parents resulted in decreased psychomotor restlessness and, subsequently, better control of food intake and prevention of weight gain.ConclusionThis paper has emphasis on the importance of a multidisciplinary approach, as well as experience from clinical practice in the treatment of complex and rare syndrome diseases.Disclosure of interestThe authors have not supplied their declaration of competing interest.