Next-generation gene panel testing in adolescents and adults in a medical neuropsychiatric genetics clinic

Intellectual disability (ID) encompasses a clinically and genetically heterogeneous group of neurodevelopmental disorders that may present with psychiatric illness in up to 40% of cases. Despite the evidence for clinical utility of genetic panels in pediatrics, there are no published studies in adolescents/adults with ID or autism spectrum disorder (ASD). This study was approved by our institutional research ethics board. We retrospectively reviewed the medical charts of all patients evaluated between January 2017 and December 2019 in our adult neuropsychiatric genetics clinic at the McGill University Health Centre (MUHC), who had undergone a comprehensive ID/ASD gene panel. Thirty-four patients aged > 16 years, affected by ID/ASD and/or other neuropsychiatric/behavioral disorders, were identified. Pathogenic or likely pathogenic variants were identified in one-third of our cohort (32%): 8 single-nucleotide variants in 8 genes (CASK, SHANK3, IQSEC2, CHD2, ZBTB20, TREX1, SON, and TUBB2A) and 3 copy number variants (17p13.3, 16p13.12p13.11, and 9p24.3p24.1). The presence of psychiatric/behavioral disorders, regardless of the co-occurrence of ID, and, at a borderline level, the presence of ID alone were associated with positive genetic findings (p = 0.024 and p = 0.054, respectively). Moreover, seizures were associated with positive genetic results (p = 0.024). One-third of individuals presenting with psychiatric illness who met our red flags for Mendelian diseases have pathogenic or likely pathogenic variants which can be identified using a comprehensive ID/ASD gene panel (~ 2500 genes) performed on an exome backbone.

17q23.3 de novo microdeletion involving only TANC2 gene: A new case

Neurodevelopmental disorders (NDDs) show a wide range of overlapping clinical features. Intellectual disability (ID), developmental delay (DD), autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD), language and communication disorders with or without motor abnormalities and/or epilepsy have been reported associated to single or multiple genes but in many cases the genetic basis remains unknown. The increasingly use of array-CGH has significantly improved the yield of diagnosing genomic disorders and led to the identification of several novel microdeletion and microduplication syndromes. TANC2 encodes a synaptic scaffold protein interacting with multiple neuropsychiatric disorder-related postsynaptic density (PSD) proteins in dendrites. Here, we describe a new case of TANC2 gene disruption in a 17q23.3 de novo microdeletion identified by array-CGH. The patient presented craniofacial dysmorphic features, hypotonia, and severe cognitive and motor impairment. In conclusion, our data add a further line of evidence supporting the role of TANC2 in NDDs and will help further researches to elucidate the regulatory mechanism of synaptic function and plasticity related to TANC2 haploinsufficiency.

Structural brain anomalies in Cri-du-Chat syndrome: MRI findings in 14 patients and possible genotype-phenotype correlations

INTRODUCTION

Cri-du-Chat Syndrome (CdCS) is a genetic condition due to deletions showing different breakpoints encompassing a critical region on the short arm of chromosome 5, located between p15.2 and p15.3, first defined by Niebuhr in 1978. The classic phenotype includes a characteristic cry, peculiar facies, microcephaly, growth retardation, hypotonia, speech and psychomotor delay and intellectual disability. A wide spectrum of clinical manifestations can be attributed to differences in size and localization of the 5p deletion. Several critical regions related to some of the main features (such as cry, peculiar facies, developmental delay) have been identified. The aim of this study is to further define the genotype-phenotype correlations in CdCS with particular regards to the specific neuroradiological findings.

PATIENTS AND METHODS

Fourteen patients with 5p deletions have been included in the present study. Neuroimaging studies were conducted using brain Magnetic Resonance Imaging (MRI). Genetic testing was performed by means of comparative genomic hybridization (CGH) array at 130 kb resolution.

RESULTS

MRI analyses showed that isolated pontine hypoplasia is the most common finding, followed by vermian hypoplasia, ventricular anomalies, abnormal basal angle, widening of cavum sellae, increased signal of white matter, corpus callosum anomalies, and anomalies of cortical development. Chromosomal microarray analysis identified deletions ranging in size from 11,6 to 33,8 Mb on the short arm of chromosome 5. Then, we took into consideration the overlapping and non-overlapping deleted regions. The goal was to establish a correlation between the deleted segments and the neuroradiological features of our patients.

CONCLUSIONS

Performing MRI on all the patients in our cohort, allowed us to expand the neuroradiological phenotype in CdCS. Moreover, possible critical regions associated to characteristic MRI findings have been identified.

[Multi-organ failure after massive Levothyroxine ingestion: case report]

Levothyroxine is the drug of choice prescribed worldwide for the treatment of Hypothyroidism. The exact daily dosage, mode of consumption and refractoriness to therapy are still subject of discussion. The intoxication with levothyroxine is rare and with severe complications in adults; on the contrary, high prevalence and benign course is observed in pediatric age. We report the case of a 56 year-old woman, presented to the emergency department after intentional ingestion of massive levothyroxine overdose , with acute renal failure, severe disturbances of cardiovascular and central nervous system, that required intensive care support. In absence of a specific treatment, plasmapheresis has been used with good results, despite important clinical complications. In fact the clinical applications of plasmapheresis are rapidly increasing in number and scope: the plasmapheresis appears to be a very important tool for the treatment of acute and severe forms of thyrotoxicosis due to l-thyroxine intoxication.

[Crouzon's syndrome. Description of a case treated surgically in the fifth month of life]

The authors describe a case of Crouzon syndrome, characterized by unusually early and serious symptoms, and surgically corrected during the fifth month of life, with good clinical and aesthetic results.