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Deletion of chromosome 22q11 concerns nearly 1/5.000 births, and is the most frequent interstitial microdeletion. The deletion generates various phenotypes which were initially regarded as distinct syndromes. 1) Di George syndrome was described in 1962 by immunologists, and associates thymic and parathyroid hypoplasia, cardiac malformation, and dysmorphic face; the prognosis is severe, as Di George syndrome is a life-threatening condition. 2) The velocardiofacial syndrome was described in 1978 by stomatologists, and associates palate abnormalities, cardiac malformations, dysmorphic faces, and learning disabilities. 3) The Takao syndrome was described in the late seventies by cardiologists as a clinical condition associating cardiac abnormalities and dysmorphic faces. During the nineties, a common molecular etiology was identified, and a new name proposed: CATCH 22, an acronyme for Cardiac abnormalities, Abnormal face, Thymic hypoplasia, Cleft palate, Hypocalcemia, deleted chromosome 22. Furthermore, new phenotypes have been recently recognized, most of them belonging to the psychiatric spectrum. Descriptive studies of large samples of children with 22q11 deletion, conducted, both in the United States and european countries, have shown the following pattern of associated symptoms:--abnormal face (100%), which expression varies with age, and can be discrete;--cardiac abnormalities (84%), including cardiac malformations of conotroncal types;--mouth abnormalities (49%), including cleft palate (14%), and velar dysfunction (20%);--urinary tract abnormalities (36%), including ureteric reflux, lung dysplasia;--transitory hypocalcemia (60%) mostly during infancy, and due to transitory hypoparathyroid dysfunction;--seizures (21%), which are usually a consequence of hypocalcemia;--immunodeficiency (1%), which worsens the prognosis. Deletion of chromosome 22q11 has been also associated with various psychiatric phenotypes, which can be classified into two groups, developmental abnormalities and psychiatric conditions. The great majority of patients with the deletion exhibit impairment of language and motor development, mild mental retardation, persistent coordination deficits, and poor academic performance. The deletion of chromosome 22q11 is also associated with high frequency of behavioral disorder with attention deficit during childhood, and with high frequency of psychotic disorder (bipolar disorder, and schizophrenia) during adolescence and young adulthood. The link between the 22q11 deletion and schizophrenia has been also supported by recent studies showing that the rate of 22q11 deletion in adults with schizophrenia (2%) is higher than it is in the general population. The rate may even be higher (6%) in subjects with childhood onset schizophrenia. The present work reviews the psychiatric literature associated with 22q11 deletion. We also report a case of 22q11 deletion in a 17-year-old girl that was initially diagnosed as paranoid schizophrenia. We will discuss the diagnostic, prognostic, and therapeutic consequences that such a genetic diagnosis implies. In the case reported here, transitory hypocalcemia induced: 1) dystonic symptoms that was believed to be catatonic symptoms or neuroleptic secondary effects, by clinicians; 2) a poor response to neuroleptic medication.