Small chromosomal aberrations (copy number variations, genomic imbalances) may confer a risk for schizophrenia, as with the 22q11.2 Deletion Syndrome (22q11.2 DS). This common microdeletion syndrome presents with congenital and late-onset features including a high risk for neuropsychiatric diseases (up to a 25% risk for schizophrenia) (Karayiorgou et al., 1995; Bassett et al., 2005). Attempts to correlate the occurrence of schizophrenia with the extent of the deletion in these patients have been unsuccessful. An increase in the susceptibility to schizophrenia may involve the altered expression of several genes within the 22q11.2 region (Meechan et al., 2007; Sivagnanasundaram et al., 2007), and this may explain the lack of replicable results from studies aiming to implicate individual genes from the deletion region as general susceptibility genes for schizophrenia (Glaser et al., 2006).
