PDD-NOS, psychotic features and executive function deficits in a boy with proximal 22q11.2 microduplication: Evolution of the psychiatric symptom profile from childhood to adolescence

The effectiveness and tolerability of pharmacotherapy for psychosis in 22q11.2 Deletion Syndrome: A systematic review

OBJECTIVE

The 22q11.2 Deletion Syndrome (22q11.2DS) is the most common microdeletion in humans with over 180 phenotypic expressions. Approximately 30-40% of affected individuals will develop psychosis and 25% meet the criteria for schizophrenia. Despite this, pharmacotherapy for managing psychosis in 22q11.2DS is poorly understood and 22q11.2DS psychosis is frequently labelled as treatment resistant. The objectives of this paper are to evaluate the effectiveness and tolerability of pharmacotherapy for 22q11.2DS psychosis and evaluate the evidence for treatment resistance.

METHOD

A systematic search was performed using CINAHL, The Cochrane Library (Cochrane Database of Systematic Reviews; Cochrane Central Register of Controlled Trials and Cochrane Clinical Answers), EMBASE, PsycINFO, PubMed, Scopus and Web of Science Core Collection from inception to December 2022. It yielded 39 case reports, 6 case series and 1 retrospective study which met the inclusion criteria.

RESULTS

Based on the current literature, individuals with 22q11.2DS psychosis experience a greater rate of medical co-morbidities such as cardiac arrhythmias, seizures and movement disorders, which complicate pharmacotherapy. Poor tolerability rather than poor clinical response motivates the switching of antipsychotics, which may explain the labelling of treatment resistance in the literature.

CONCLUSION

There are insufficient data to recommend a single antipsychotic for 22q11.2DS psychosis. Nonetheless, with proactive management of co-morbidities, antipsychotic medication in 22q11.2DS psychosis is an effective treatment commonly resulting in improvement in quality of life.

Modeling and Predicting Developmental Trajectories of Neuropsychiatric Dimensions Associated With Copy Number Variations

Copy number variants, such as duplications and hemizygous deletions at chromosomal loci of up to a few million base pairs, are highly associated with psychiatric disorders. Hemizygous deletions at human chromosome 22q11.2 were found to be associated with elevated instances of schizophrenia and autism spectrum disorder in 1992 and 2002, respectively. Following these discoveries, many mouse models have been developed and tested to analyze the effects of gene dose alterations in small chromosomal segments and single genes of 22q11.2. Despite several limitations to modeling mental illness in mice, mouse models have identified several genes on 22q11.2-Tbx1, Dgcr8, Comt, Sept5, and Prodh-that contribute to dimensions of autism spectrum disorder and schizophrenia, including working memory, social communication and interaction, and sensorimotor gating. Mouse studies have identified that heterozygous deletion of Tbx1 results in defective social communication during the neonatal period and social interaction deficits during adolescence/adulthood. Overexpression of Tbx1 or Comt in adult neural progenitor cells in the hippocampus delays the developmental maturation of working memory capacity. Collectively, mouse models of variants of these 4 genes have revealed several potential neuronal mechanisms underlying various aspects of psychiatric disorders, including adult neurogenesis, microRNA processing, catecholamine metabolism, and synaptic transmission. The validity of the mouse data would be ultimately tested when therapies or drugs based on such potential mechanisms are applied to humans.

A Not So Benign Family Pedigree With Hereditary Chorea: A Broader Phenotypic Expression or Additional Picture?

NKX2-1 mutations have been usually associated with a non-progressive neurological disease. Recent reports revealed a vast variability regarding its clinical expressivity. Aim of this work was widening the Benign Hereditary Chorea neurological, cognitive and behavioral phenotype through the description of a child and her family pedigree. Molecular analysis focused on NKX2-1 gene revealed a novel frameshift mutation in the three-generation members described. Cognitive scales detected a relevant developmental delay, and the clinical observation and Autism Diagnostic Observation Schedule -2 administration allowed the diagnosis of autism spectrum disorder in the proband. Microarray testing, further executed to exclude a double hit contextually provoking the complex neurodevelopmental disorder, revealed the 22q11.2 Duplication Syndrome. This paper may contribute to enlarge Benign Hereditary Chorea variable expressivity and, together with other studies reported in the literature, underlines the need to reconsider the term "benign," verifying the opportunity of more a complex diagnosis.

Episodic Behavioural Regression in an 8-Year-Old Female: Sequelae of 22q11.2 Duplication Syndrome

22q11.2 duplication syndrome is a recently discovered genetic syndrome with unclear neuropsychiatric sequelae. While its connection to 22q11.2 deletion syndrome is actively investigated, case reports on the neuropsychiatric sequelae of affected individuals have been previously described, largely focusing on comorbid autism spectrum disorder. Here, we present the case of an 8-year-old female experiencing episodes of severe behavioural regression following medical illness. We analyze the case and relate it to the available literature and identify potential risk factors.

Critical reappraisal of mechanistic links of copy number variants to dimensional constructs of neuropsychiatric disorders in mouse models

Copy number variants are deletions and duplications of a few thousand to million base pairs and are associated with extraordinarily high levels of autism spectrum disorder, schizophrenia, intellectual disability, or attention-deficit hyperactivity disorder. The unprecedented levels of robust and reproducible penetrance of copy number variants make them one of the most promising and reliable entry points to delve into the mechanistic bases of many mental disorders. However, the precise mechanistic bases of these associations still remain elusive in humans due to the many genes encoded in each copy number variant and the diverse associated phenotypic features. Genetically engineered mice have provided a technical means to ascertain precise genetic mechanisms of association between copy number variants and dimensional aspects of mental illnesses. Molecular, cellular, and neuronal phenotypes can be detected as potential mechanistic substrates for various behavioral constructs of mental illnesses. However, mouse models come with many technical pitfalls. Genetic background is not well controlled in many mouse models, leading to rather obvious interpretative issues. Dose alterations of many copy number variants and single genes within copy number variants result in some molecular, cellular, and neuronal phenotypes without a behavioral phenotype or with a behavioral phenotype opposite to what is seen in humans. In this review, I discuss technical and interpretative pitfalls of mouse models of copy number variants and highlight well-controlled studies to suggest potential neuronal mechanisms of dimensional aspects of mental illnesses. Mouse models of copy number variants represent toeholds to achieve a better understanding of the mechanistic bases of dimensions of neuropsychiatric disorders and thus for development of mechanism-based therapeutic options in humans.