Deinstitutionalization of psychiatric patients and people with intellectual disabilities has markedly increased the number of referrals of patients with behavioural disturbances and/or psychiatric to outpatient psychiatrist, frequently because of’treatment resistant’ psychiatric syndromes. Given the rapidly growing knowledge of clinical and molecular genetics, co-occurrence of psychological and behavioural dysfunctions with a chromosomal anomaly in an individual patient greatly increases the possibilities for an etiological explanation of the clinical picture, which in turn may serve as guidance for a specific treatment.

To elucidate the phenotype-genotype relation in patients with unexplained behavioural problems.

To advocate the clinical awareness of so called behavioural phenotype.

Detailed presentation of some cases (diagnosis and treatment) that are referred to the outpatient department for neuropsychiatry and who are published by the research group’Psychopathology and Genetics’.

Female (25yrs;IQ:50), reason of referral: psychotic disorder. D/anxieties due to overestimation; de novo duplication 13(q14.1q21.3). Female (30yrs;IQ:< 60) referred for psychotic and autistic symptoms. D/cognitive alexithymia; de novo r21. Female (17yrs;IQ:81), referred for difficulties in school performance. D/panic disorder; distal 22q11 microdeletion. Male (57yrs;IQ:128), reason of referral: treatment resistant depression. D/no psychopathology; Robertsonian translocation 13;14. Female (57yrs;IQ< 60), referred presenile dementia. D/mucopolysaccharidosis SanfilippoB. Male (21yrs;IQ:52). Referred for mood instability. History: XXY. D/atypical bipolar disorder; PWS + XXY.

In patients referred for recurrent challenging behaviours and/or psychiatric symptoms the search for a genetic etiology is mandatory in order to avoid erratic treatment advises.