22q11.2 deletion syndrome (22q11.2DS) results from a hemizygous microdeletion on chromosome 22 and is characterized by phenotypic variability. Several studies have been conducted on the impact of COMT functional polymorphism in 22q11DS, suggesting that attenuated psychotic manifestations are frequent in children and adolescents and represent one of the strongest predictors for the onset of psychotic disorder.

We explored possible interaction between COMT polymorphism and subclinical psychiatric symptoms in a 22q11.2DS cohort of 42 participants aged 6 to 26 years: 17 hemizygosity for COMT-Met and 25 hemizygosity for COMT-Val.

To analyse impact of COMT gene in 22q11DS and its related psychiatric correlates.

Each participant, genotyped for the catechol O-methyltransferase (COMT) Met/Val polymorphism, underwent structured psychiatric and cognitive assessment. Analysis of positive and negative symptoms was performed by the structured interview for prodromal syndromes (SIPS). Finally, longitudinal data available in a subsample of 24 individuals were used to explore the developmental trajectories of psychotic symptoms one year later.

There was a significant positive correlation between COMT Val polymorphism and positive symptoms; at follow-up, no significant correlation were found between COMT polymorphism and psychiatric symptoms. No other significant differences were found between groups (Comt/Met-Comt/Val) on any other CBCL or QI score.

COMT and additional genes microdeleted might interact in the susceptibility to schizophrenia in 22q11.2DS: psychotic symptoms might result from an epistatic interaction with other genes. Moreover, gene-environment, in presence of genetic vulnerability could increase the risk of schizophrenia in 22q11DS.

The authors have not supplied their declaration of competing interest.