Investigation of SNP rs2060546 Immediately Upstream to NTN4 in a Danish Gilles de la Tourette Syndrome Cohort

Trichotillomania is more related to Tourette disorder than to obsessive-compulsive disorder

OBJECTIVE

Trichotillomania (TTM) is characterized by the pulling out of one's hair. TTM was classified as an impulse control disorder in DSM-IV, but is now classified in the obsessive-compulsive related disorders section of DSM-5. Classification for TTM remains an open question, especially considering its impact on treatment of the disorder. In this review, we questioned the relation of TTM to tic disorder and obsessive-compulsive disorder (OCD).

METHOD

We reviewed relevant MEDLINE-indexed articles on clinical, neuropsychological, neurobiological, and therapeutic aspects of trichotillomania, OCD, and tic disorders.

RESULTS

Our review found a closer relationship between TTM and tic disorder from neurobiological (especially imaging) and therapeutic standpoints.

CONCLUSION

We sought to challenge the DSM-5 classification of TTM and to compare TTM with both OCD and tic disorder. Some discrepancies between TTM and tic disorders notwithstanding, several arguments are in favor of a closer relationship between these two disorders than between TTM and OCD, especially when considering implications for therapy. This consideration is essential for patients.

Clinical and genetic analysis of children with a dual diagnosis of Tourette syndrome and autism spectrum disorder

Gilles de la Tourette Syndrome (TS) is a neurodevelopmental disorder that causes children to make repeated, brief involuntary movements or sounds. TS can be co-morbid with other neurodevelopmental disorders, including autism spectrum disorder (ASD). Clusters of biologically related genes have been associated with neurodevelopmental disorders, suggesting shared pathologies. However, the genetic contribution to TS remains poorly defined. We asked whether children with both TS and ASD differed clinically from children with ASD alone, and identified potentially deleterious genetic events in children with TS and ASD. We compared clinical data from 119 children with ASD and TS to 2603 children with ASD, all from the Simons Simplex Collection. We performed gene set enrichment analysis on de novo genetic events in children with both TS and ASD to identify candidate genes and pathways, and compared these genes and pathways with those previously identified in TS. Children with TS and ASD were diagnosed at an older age, had higher IQ scores, and had more restricted and repetitive behavior than children with ASD but not TS. Gene Ontology analysis revealed that proteins important for specific biological pathways, including regulation of calcium ion-dependent exocytosis, basement membrane organization, and visual behavior and learning, and specific cellular pathways, including basal lamina and ciliary transition zone, are enriched among genes with de novo mutations in children with TS and ASD. Clinical and genetic analysis of cohorts of affected children can help to determine the underlying pathophysiology of TS and other neurodevelopmental disorders.

Genetic Approaches to Understanding Psychiatric Disease

Human genetic studies have been the driving force in bringing to light the underlying biology of psychiatric conditions. As these studies fill in the gaps in our knowledge of the mechanisms at play, we will be better equipped to design therapies in rational and targeted ways, or repurpose existing therapies in previously unanticipated ways. This review is intended for those unfamiliar with psychiatric genetics as a field and provides a primer on different modes of genetic variation, the technologies currently used to probe them, and concepts that provide context for interpreting the gene-phenotype relationship. Like other subfields in human genetics, psychiatric genetics is moving from microarray technology to sequencing-based approaches as barriers of cost and expertise are removed, and the ramifications of this transition are discussed here. A summary is then given of recent genetic discoveries in a number of neuropsychiatric conditions, with particular emphasis on neurodevelopmental conditions. The general impact of genetics on drug development has been to underscore the extensive etiological heterogeneity in seemingly cohesive diagnostic categories. Consequently, the path forward is not in therapies hoping to reach large swaths of patients sharing a clinically defined diagnosis, but rather in targeting patients belonging to specific "biotypes" defined through a combination of objective, quantifiable data, including genotype.