Dopamine dysfunction in 22q11 deletion syndrome: possible cause of motor symptoms

Role of COMT V158M Polymorphism in the Development of Dystonia after Administration of Antipsychotic Drugs

Antipsychotics (APDs) represent the main pharmacological strategy in the treatment of schizophrenia; however, their administration often may result in severe adverse effects, such as extrapyramidal symptoms. Typically, dystonic movements are considered the result of impaired function and/or abnormalities of dopaminergic neurotransmission/signaling in the basal ganglia. The catechol O-methyltransferase (COMT) gene is located within the 22q11.2 region, and its product is an enzyme involved in transferring a methyl group from S-adenosylmethionine to catecholamines, including dopamine. Studies showed that COMT Val158Met polymorphism modifies enzymatic activity and, consequently, synaptic dopamine concentration in specific brain areas. We identified a patient with 22q11.2 deletion syndrome presenting with cervical and trunk dystonia after paliperidone administration, which persisted even after drug discontinuation. Given the patient’s genetic condition, we hypothesized that the dopaminergic dysfunction had been aggravated by COMT involvement, thus causing dystonia. In line with this hypothesis, we carried out a study on psychiatric patients in chronic treatment with APD to evaluate the distribution of the COMT Val158Met polymorphism and its role in the onset of adverse extrapyramidal symptoms. The study included four patients with dystonia after administration of APDs compared to 17 patients who never presented adverse drug reactions. Our data suggest that the Val/Val and Met/Met polymorphisms of the COMT gene are associated with a protective effect for the development of collateral extrapyramidal symptoms in patients treated with APDs, while the Val/Met genotype could be considered a risk factor for the development of dystonia after APDs administration.

22q11 microdeletion syndrome and ultra-high risk for psychosis: The role of neurological soft signs as an independent marker of vulnerability for psychosis

AIM

22q11 microdeletion syndrome has an increased risk for psychosis, similar to subjects at ultra-high risk for psychosis. Neurological soft signs are considered an endophenotype of psychotic disorders and a marker of vulnerability to Schizophrenia, consisting of overflow movements, dysrhythmia and speed of timed activities. To date, there are no studies that have evaluated the presence of the neurological soft signs in subjects with 22q11 microdeletion syndrome and there are a few studies that have analysed this issue in subjects at ultra-high risk.

METHODS

We sought to measure neurological soft signs in these two conditions, compared to healthy controls and to analyse the possible correlation between neurological soft signs and positive/negative symptoms both in 22q11 microdeletion syndrome and ultra-high-risk groups. 54 drug-naive patients (29 with 22q11 microdeletion syndrome and 25 at ultra-high risk for psychosis) and 25 healthy controls were evaluated for neurological soft signs.

RESULTS

Both clinical groups showed a greater number of neurological soft signs compared to healthy control, although the two clinical groups did not differ for the number of neurological soft signs. Positive correlation between speed of timed activities and negative symptoms was found in subjects at ultra-high risk.

CONCLUSION

Neurological soft signs could represent a marker of atypical neurodevelopment in the two populations examined. Since we did not found a strong correlation between neurological soft signs and positive/negative symptoms, we suggest that neurological soft signs could be indicators of vulnerability to psychosis independent from the psychopathology.