When rare meets common: Treatable genetic diseases are enriched in the general psychiatric population.

Mental illnesses are one of the biggest contributors to the global disease burden. Despite the increased recognition, diagnosis and ongoing research of mental health disorders, the etiology and underlying molecular mechanisms of these disorders are yet to be fully elucidated. Moreover, despite many treatment options available, a large subset of the psychiatric patient population is nonresponsive to standard medications and therapies. There has not been a comprehensive study to date examining the burden and impact of treatable genetic disorders (TGDs) that can present with neuropsychiatric features in psychiatric patient populations. In this study, we test the hypothesis that TGDs that present with psychiatric symptoms are more prevalent within psychiatric patient populations compared to the general population by performing targeted next-generation sequencing of 129 genes associated with 108 TGDs in a cohort of 2301 psychiatric patients. In total, 48 putative affected and 180 putative carriers for TGDs were identified, with known or likely pathogenic variants in 79 genes. Despite screening for only 108 genetic disorders, this study showed a two-fold (2.09%) enrichment for genetic disorders within the psychiatric population relative to the estimated 1% cumulative prevalence of all single gene disorders globally. This strongly suggests that the prevalence of these, and most likely all, genetic diseases is greatly underestimated in psychiatric populations. Increasing awareness and ensuring accurate diagnosis of TGDs will open new avenues to targeted treatment for a subset of psychiatric patients.

The Diagnostic Landscape of Adult Neurogenetic Disorders.

Neurogenetic diseases affect individuals across the lifespan, but accurate diagnosis remains elusive for many patients. Adults with neurogenetic disorders often undergo a long diagnostic odyssey, with multiple specialist evaluations and countless investigations without a satisfactory diagnostic outcome. Reasons for these diagnostic challenges include: (1) clinical features of neurogenetic syndromes are diverse and under-recognized, particularly those of adult-onset, (2) neurogenetic syndromes may manifest with symptoms that span multiple neurological and medical subspecialties, and (3) a positive family history may not be present or readily apparent. Furthermore, there is a large gap in the understanding of how to apply genetic diagnostic tools in adult patients, as most of the published literature focuses on the pediatric population. Despite these challenges, accurate genetic diagnosis is imperative to provide affected individuals and their families guidance on prognosis, recurrence risk, and, for an increasing number of disorders, offer targeted treatment. Here, we provide a framework for recognizing adult neurogenetic syndromes, describe the current diagnostic approach, and highlight studies using next-generation sequencing in different neurological disease cohorts. We also discuss diagnostic pitfalls, barriers to achieving a definitive diagnosis, and emerging technology that may increase the diagnostic yield of testing.

Exome and genome sequencing in adults with undiagnosed disease: a prospective cohort study.

BACKGROUND: Exome and genome sequencing have been demonstrated to increase diagnostic yield in paediatric populations, improving treatment options and providing risk information for relatives. There are limited studies examining the clinical utility of these tests in adults, who currently have limited access to this technology. METHODS: Patients from adult and cancer genetics clinics across Toronto, Ontario, Canada were recruited into a prospective cohort study evaluating the diagnostic utility of exome and genome sequencing in adults. Eligible patients were ≥18 years of age and suspected of having a hereditary disorder but had received previous uninformative genetic test results. In total, we examined the diagnostic utility of exome and genome sequencing in 47 probands and 34 of their relatives who consented to participate and underwent exome or genome sequencing. RESULTS: Overall, 17% (8/47) of probands had a pathogenic or likely pathogenic variant identified in a gene associated with their primary indication for testing. The diagnostic yield for patients with a cancer history was similar to the yield for patients with a non-cancer history (4/18 (22%) vs 4/29 (14%)). An additional 24 probands (51%) had an inconclusive result. Secondary findings were identified in 10 patients (21%); three had medically actionable results. CONCLUSIONS: This study lends evidence to the diagnostic utility of exome or genome sequencing in an undiagnosed adult population. The significant increase in diagnostic yield warrants the use of this technology. The identification and communication of secondary findings may provide added value when using this testing modality as a first-line test.

High Rates of Genetic Diagnosis in Psychiatric Patients with and without Neurodevelopmental Disorders: Toward Improved Genetic Diagnosis in Psychiatric Populations.

OBJECTIVE: There is a paucity of literature on genetic diagnosis in psychiatric populations, particularly the vulnerable population of patients with concomitant neurodevelopmental disorder (NDD). In this cross-sectional study, we investigated the genetic diagnostic rate in 151 adult psychiatric patients from two centers in Ontario, Canada, including a large subset (73.5%) with concurrent NDD, and performed phenotypic analysis to determine the strongest predictors for the presence of a genetic diagnosis. METHOD: Patients 16 years of age or older and affected with a psychiatric disorder plus at least one of NDD, neurological disorder, congenital anomaly, dysmorphic features, or family history of NDD were recruited through the genetics clinics between 2012 and 2016. Patients underwent genetic assessment and testing according to clinical standards. Chi-squared test was used for phenotypic comparisons. Multivariate logistic regression analysis was performed to determine which phenotypic features were predictive of genetic diagnosis types. RESULTS: Overall, 45.7% of patients in the total cohort were diagnosed with genetic disorders with the vast majority of diagnoses (89.9%) comprising single gene and chromosomal disorders. There were management and treatment implications for almost two-thirds (63.8%) of diagnosed patients. Presence of a single gene disorder or chromosomal diagnosis was predicted by differing combinations of neurological, NDD, and psychiatric phenotypes. CONCLUSION: The results of this study highlight the frequency and impact of genetic diagnosis in psychiatric populations, particularly those with concomitant NDD. Genetic assessment should be considered in psychiatric patients, particularly those with multiple brain phenotypes (psychiatric, neurodevelopmental, neurological).

Utilization of the 2017 diagnostic criteria for hEDS by the Toronto GoodHope Ehlers-Danlos syndrome clinic: A retrospective review.

The new 2017 diagnostic criteria for hypermobile Ehlers-Danlos Syndrome (hEDS) provide a framework for diagnosing hEDS but are more stringent than the previous Villefranche criteria. Our clinical experience at the GoodHope EDS clinic was that the 2017 criteria left many highly symptomatic patients without a diagnosis of hEDS. We conducted a retrospective cohort study to confirm our clinic experience and assess the accuracy of the 2017 diagnostic criteria for hEDS in patients who had a previous hEDS diagnosis based on the Villefranche criteria. Our study found that 15% (n = 20 of 131) of patients with a prior diagnosis of hEDS met the 2017 diagnostic criteria, and many of the traits used to distinguish hEDS were not significantly more frequent in patients who met 2017 criteria versus those who did not. In both groups objective systemic manifestations were found less frequently than subjective systemic manifestations. Beighton score (BS) as assessed by primary care practitioner was found to be higher than assessment by EDS practitioner in 81% (n = 74 of 91) of cases. Generalized joint hypermobility was confirmed in only 46% (n = 51 of 111) of patients who had a previous diagnosis of hEDS. Higher BS did not correlate with increased number of systemic manifestations in our cohort. Common comorbidities of hEDS were found with similar frequency in those who met 2017 criteria and those who did not. Based on our cohort, the 2017 hEDS diagnostic criteria require refinement to improve its diagnostic accuracy.

Adult patient perspectives on phenylketonuria care: Highlighting the need for dedicated adult management and services.

Phenylketonuria (PKU) is an autosomal recessive metabolic disorder characterized by an inability to metabolize the amino acid phenylalanine (Phe). If left untreated, an accumulation of Phe results in neurodevelopmental, neurological and psychological impairments. Advancements in detection and treatment of PKU have improved outcomes and life expectancy for these patients, emphasizing the need for life-long, specialized care. Due to the paucity of adult-focused PKU clinics, patients who are well into adulthood are still being treated in pediatric centers. This retrospective study evaluates the perceived expectations, benefits and challenges of 50 adult PKU patients (mean age 31.3 ± 10.4 years) transitioning from a pediatric to adult care setting using a transition questionnaire administered at the first clinic visit at the adult PKU care center. Patients reported a lack of access to adult resources and adult-specific PKU educational material in their pediatric PKU clinic. In contrast, the established relationships with the pediatric health care team and familiarity with treatment plans were aspects of pediatric care that patients enjoyed. The results from this study will contribute to the optimization of adult PKU patient care, establishment of strategies for transitioning adults with PKU and other metabolic disorders from pediatric to adult care, and support the need to establish adult-only PKU care facilities.

Copy number variant syndromes are frequent in schizophrenia: Progressing towards a CNV-schizophrenia model.

The genetic underpinnings of schizophrenia (SCZ) remain unclear. SCZ genetic studies thus far have only identified numerous single nucleotide polymorphisms with small effect sizes and a handful of copy number variants (CNVs). This study investigates the prevalence of well-characterized CNV syndromes and candidate CNVs within a cohort of 348 SCZ patients, and explores correlations to their phenotypic findings. There was an enrichment of syndromic CNVs in the cohort, as well as brain-related and immune pathway genes within the detected CNVs. SCZ patients with brain-related CNVs had increased CNV burden, neurodevelopmental features, and types of hallucinations. Based on these results, we propose a CNV-SCZ model wherein specific phenotypic profiles should be prioritized for CNV screening within the SCZ patient population.

Understanding the schizophrenia phenotype in the first patient with the full SCN2A phenotypic spectrum.

The sodium voltage-gated channel α subunit 2 (SCN2A) gene encodes a subunit of sodium voltage-gated channels expressed primarily in the central nervous system that are responsible for action potential initiation and propagation in excitable cells. SCN2A mutations underlie a spectrum of distinct phenotypes, including seizure disorders, neurodevelopmental disorders, and rarer instances of episodic ataxia and schizophrenia. We report on a 38-year-old patient with adult-onset psychotic symptoms on a background of infantile-onset seizures, autistic features and episodic ataxia. Whole-exome sequencing revealed a de-novo novel SCN2A mutation (c.4966T > C, p.Ser1656Pro). This and other SCN2A mutations associated with the schizophrenia phenotype overlap those seen in neurodevelopmental disorders, suggesting a common underlying mechanism. This is the first report of a patient with the entire known SCN2A phenotypic spectrum. We highlight the importance of recognizing the psychiatric phenotypes associated with SCN2A mutations and that the phenotypic spectrum is more fluid, and less categorical, than previously thought.

The Nose Knows or Does it? Olfactory Reference Syndrome in Patients Presenting for Assessment of Unusual Body Odor.

Olfactory reference syndrome (ORS) is a rarely diagnosed psychiatric disorder in which individuals falsely believe that they emit an offensive body odor. This retrospective cohort study characterizes the clinical and demographic features of 54 individuals who presented to a Canadian genetics clinic for query trimethylaminuria (TMAU), an inherited disorder in which a pungent fishy odor is produced. The majority (83%) were found to have a likely diagnosis of ORS and a high rate (73.3%) of concomitant psychiatric disorders; only two patients were diagnosed with TMAU. This study highlights the genetics clinic as an unexpected and major ascertainment point for ORS, and shows that ORS can be differentiated from TMAU by age of onset (~28 years), odor characterization (refuse-related), and the presence of associated comorbid psychiatric diagnoses. There is a low diagnostic rate of ORS, attesting to the need for improved education and awareness.

Enrichment of pathogenic variants in genes associated with inborn errors of metabolism in psychiatric populations.

Many genetic conditions can mimic mental health disorders, with psychiatric symptoms that are difficult to treat with standard psychotropic medications. This study tests the hypothesis that psychiatric populations are enriched for pathogenic variants associated with selected inborn errors of metabolism (IEMs). Using next-generation sequencing, 2046 psychiatric patients were screened for pathogenic variants in genes associated with four IEMs, Niemann-Pick disease type C (NPC), Wilson disease (WD), homocystinuria (HOM), and acute intermittent porphyria (AIP). Among the 2046 cases, carrier rates of 0.83, 0.98, and 0.20%, for NPC, WD and HOM, and affected rates of 0.10 and 0.24% for NPC and AIP were seen, respectively. An enrichment of known and predicted pathogenic variants in the genes associated with NPC and AIP was found in the psychiatric cohort and especially in schizophrenia patients. The results of this study support that pathogenic variants in genes associated with IEMs are enriched in psychiatric populations. Underlying undiagnosed IEMs could account for the psychiatric symptomatology in a subset of psychiatric patients. Further studies are warranted to investigate the possibility that carriers for IEMs may have an increased risk for psychiatric disorders, particularly in the context of poor treatment response.

Oculoleptomeningeal Amyloidosis Secondary to the Rare Transthyretin c.381T>G (p.Ile127Met) Mutation.

BACKGROUND: Oculoleptomeningeal amyloidosis (OLMA) represents a rare subtype of familial transthyretin (TTR) amyloidosis, characterized by deposition of amyloid in cranial and spinal leptomeninges along with ocular involvement. Of >100 TTR mutations identified, few have been associated with OLMA. Herein we describe the first report of leptomeningeal amyloidosis associated with the c.381T>G (p.Ile127Met) TTR mutation, linking this variant to the OLMA phenotype. CASE DESCRIPTION: A 53 year-old man presented with a 2-year history of progressive symptoms including upper and lower limb weakness, ataxia, and peripheral and autonomic neuropathy. Neuroimaging, including gadolinium-enhanced magnetic resonance imaging of the brain and spinal axis, identified diffuse leptomeningeal enhancement along the brainstem and spinal cord plus evidence of hemosiderosis. Pathologic and genetic analyses of biopsy material from enhancing intradural extramedullary tissue at the thoracolumbar junction was diagnostic of amyloidosis of a transthyretin type secondary to a TTR c.381T>G (p.Ile127Met) mutation. CONCLUSIONS: OLMA represents a rare subtype of heritable transthyretin amyloidosis that may present with progressive neurological decline secondary to central nervous system leptomeningeal amyloid deposition. This case identifies the c.381T>G (p.Ile127Met) TTR mutation variant as being implicated in the OLMA phenotype.

Mutations in the genes for thyroglobulin and thyroid peroxidase cause thyroid dyshormonogenesis and autosomal-recessive intellectual disability.

We have used single-nucleotide polymorphism microarray genotyping and homozygosity-by-descent (HBD) mapping followed by Sanger sequencing or whole-exome sequencing (WES) to identify causative mutations in three consanguineous families with intellectual disability (ID) related to thyroid dyshormonogenesis (TDH). One family was found to have a shared HBD region of 12.1 Mb on 8q24.21-q24.23 containing 36 coding genes, including the thyroglobulin gene, TG. Sanger sequencing of TG identified a homozygous nonsense mutation Arg2336*, which segregated with the phenotype in the family. A second family showed several HBD regions, including 6.0 Mb on 2p25.3-p25.2. WES identified a homozygous nonsense mutation, Glu596*, in the thyroid peroxidase gene, TPO. WES of a mother/father/proband trio from a third family revealed a homozygous missense mutation, Arg412His, in TPO. Mutations in TG and TPO are very rarely associated with ID, mainly because TDH is generally detectable and treatable. However, in populations where resources for screening and detection are limited, and especially where consanguineous marriages are common, mutations in genes involved in thyroid function may also be causes of ID, and as TPO and TG mutations are the most common genetic causes of TDH, these are also likely to be relatively common causes of ID.

The expanding phenotypic spectrum of female SLC9A6 mutation carriers: a case series and review of the literature.

Christianson syndrome (OMIM 300243), caused by mutations in the X-linked SLC9A6 gene, is characterized by severe global developmental delay and intellectual disability, developmental regression, epilepsy, microcephaly and impaired ocular movements. It shares many common features with Angelman syndrome. Carrier females have been described as having learning difficulties with mild to moderate intellectual disability, behavioural issues and psychiatric illnesses. There is little literature on the carrier female phenotype of Christianson syndrome. We describe a large extended family with three affected males, four carrier females, one presumed carrier female and one obligate carrier female with a c.190G>T, p.E64X mutation known to cause a premature stop codon in SLC9A6. We characterize and expand the clinical phenotype of female SLC9A6 mutation carriers by comparing our described family with female carriers previously discussed in the literature. In particular, we highlight the neurodevelopmental and psychiatric phenotypes observed in our family and previous reports.

A detailed clinical analysis of 13 patients with AUTS2 syndrome further delineates the phenotypic spectrum and underscores the behavioural phenotype.

BACKGROUND: AUTS2 syndrome is an 'intellectual disability (ID) syndrome' caused by genomic rearrangements, deletions, intragenic duplications or mutations disrupting AUTS2. So far, 50 patients with AUTS2 syndrome have been described, but clinical data are limited and almost all cases involved young children. METHODS: We present a detailed clinical description of 13 patients (including six adults) with AUTS2 syndrome who have a pathogenic mutation or deletion in AUTS2. All patients were systematically evaluated by the same clinical geneticist. RESULTS: All patients have borderline to severe ID/developmental delay, 83-100% have microcephaly and feeding difficulties. Congenital malformations are rare, but mild heart defects, contractures and genital malformations do occur. There are no major health issues in the adults; the oldest of whom is now 59 years of age. Behaviour is marked by it is a friendly outgoing social interaction. Specific features of autism (like obsessive behaviour) are seen frequently (83%), but classical autism was not diagnosed in any. A mild clinical phenotype is associated with a small in-frame 5' deletions, which are often inherited. Deletions and other mutations causing haploinsufficiency of the full-length AUTS2 transcript give a more severe phenotype and occur de novo. CONCLUSIONS: The 13 patients with AUTS2 syndrome with unique pathogenic deletions scattered around the AUTS2 locus confirm a phenotype-genotype correlation. Despite individual variations, AUTS2 syndrome emerges as a specific ID syndrome with microcephaly, feeding difficulties, dysmorphic features and a specific behavioural phenotype.

Psychiatric disorders in Ehlers-Danlos syndrome are frequent, diverse and strongly associated with pain.

Ehlers-Danlos syndromes (EDS) are a heterogeneous group of hereditary connective tissue disorders characterized by joint hypermobility, widespread musculoskeletal pain and tissue fragility. Psychiatric disorders and psychosocial impairment are common, yet poorly characterized, findings in EDS patients. We investigated the frequency and types of psychiatric disorders and their relationship to systemic manifestations in a cohort of 106 classic and hypermobility type EDS patients. In this retrospective study, extensive medical chart review was performed for patients referred at two genetics clinics who were diagnosed with EDS. Statistical analysis was undertaken to determine the frequency of psychiatric disorders and association with systemic findings. Psychiatric disorders were found in 42.5% of the EDS cohort, with 22.7% of patients affected with 2 or more psychiatric diagnoses. Anxiety and depression were most commonly reported, with frequencies of 23.6 and 25.5%, respectively. A variety of other psychiatric diagnoses were also identified. Abdominal pain [odds ratio (OR) 7.38], neuropathic pain (OR 4.07), migraines (OR 5.21), joint pain (OR 2.85) and fatigue (OR 5.55) were significantly associated with the presence of a psychiatric disorder. The presence of any pain symptom was significantly associated with having a psychiatric disorder (OR 9.68). Muscle pain (OR 2.79), abdominal pain (OR 5.78), neuropathic pain (OR 3.91), migraines (OR 2.63) and fatigue (OR 3.78) were significantly associated with having an anxiety or mood disorder. Joint hypermobility and the classic dermatological features of EDS showed no significant association with having a psychiatric disorder. Our findings demonstrate a high frequency of psychiatric disorders and an association with pain symptoms in EDS.

Microdeletion 8q22.2-q22.3 in a 40-year-old male.

BACKGROUND: Interstitial deletions at chromosome 8q22.2-q22.3 have been rarely reported in the literature. To date, six patients have been described in the literature with deletions varying in size from 1.36 Mb to 6.44 Mb. These patients range in age from early childhood to early adulthood. The interstitial deletion phenotype has been described to involve moderate to severe intellectual disability, seizures and a distinct facial phenotype. We report on a 40-year-old male with a 3.351 Mb deletion at chromosome 8q22.2-q22.3 who presents with moderate intellectual disability, autism spectrum disorder, childhood seizure disorder, congenital heart defect and hearing loss. He is the oldest known patient to date. METHODS: Array comparative genomic hybridization (aCGH) was performed on DNA extracted from peripheral blood. CONCLUSION: This is the first report of an individual with chromosome 8q22.2-q22.3 interstitial deletion associated with congenital heart disease and hearing loss. Haploinsufficiency of the GRHL2 gene contained within the microdeletion is proposed as a candidate genetic mechanism for this patient's hearing loss.

Novel VPS13B Mutations in Three Large Pakistani Cohen Syndrome Families Suggests a Baloch Variant with Autistic-Like Features.

BACKGROUND: Cohen Syndrome (COH1) is a rare autosomal recessive disorder, principally identified by ocular, neural and muscular deficits. We identified three large consanguineous Pakistani families with intellectual disability and in some cases with autistic traits. METHODS: Clinical assessments were performed in order to allow comparison of clinical features with other VPS13B mutations. Homozygosity mapping followed by whole exome sequencing and Sanger sequencing strategies were used to identify disease-related mutations. RESULTS: We identified two novel homozygous deletion mutations in VPS13B, firstly a 1 bp deletion, NM_017890.4:c.6879delT; p.Phe2293Leufs*24, and secondly a deletion of exons 37-40, which co-segregate with affected status. In addition to COH1-related traits, autistic features were reported in a number of family members, contrasting with the "friendly" demeanour often associated with COH1. The c.6879delT mutation is present in two families from different regions of the country, but both from the Baloch sub-ethnic group, and with a shared haplotype, indicating a founder effect among the Baloch population. CONCLUSION: We suspect that the c.6879delT mutation may be a common cause of COH1 and similar phenotypes among the Baloch population. Additionally, most of the individuals with the c.6879delT mutation in these two families also present with autistic like traits, and suggests that this variant may lead to a distinct autistic-like COH1 subgroup.

Deletion of 15q11.2(BP1-BP2) region: further evidence for lack of phenotypic specificity in a pediatric population.

Microdeletion of the BP1-BP2 region at 15q11.2 is a recurrent copy number variant (CNV) frequently found in patients undergoing chromosomal microarray (CMA). Genetic counselling regarding this CNV is challenging due to the wide range of phenotypic presentation in reported patients and lack of general population-based data. As one of the most common reasons for CMA is childhood developmental delay, clinicians need to be cognizant of the inherent ascertainment bias in the literature. We performed a detailed medical record review for 55 patients with this 15q11.2 microdeletion and report the clinical features of the 35 patients for whom information was available. We compared our results to the recent report by Cafferkey et al. in this journal. Our conclusion is that the phenotypic spectrum is too broad and non-specific to constitute a bona fide "syndrome" and that further research must be done to delineate the contribution of this CNV to phenotype.

De novo heterozygous mutations in SMC3 cause a range of Cornelia de Lange syndrome-overlapping phenotypes.

Cornelia de Lange syndrome (CdLS) is characterized by facial dysmorphism, growth failure, intellectual disability, limb malformations, and multiple organ involvement. Mutations in five genes, encoding subunits of the cohesin complex (SMC1A, SMC3, RAD21) and its regulators (NIPBL, HDAC8), account for at least 70% of patients with CdLS or CdLS-like phenotypes. To date, only the clinical features from a single CdLS patient with SMC3 mutation has been published. Here, we report the efforts of an international research and clinical collaboration to provide clinical comparison of 16 patients with CdLS-like features caused by mutations in SMC3. Modeling of the mutation effects on protein structure suggests a dominant-negative effect on the multimeric cohesin complex. When compared with typical CdLS, many SMC3-associated phenotypes are also characterized by postnatal microcephaly but with a less distinctive craniofacial appearance, a milder prenatal growth retardation that worsens in childhood, few congenital heart defects, and an absence of limb deficiencies. While most mutations are unique, two unrelated affected individuals shared the same mutation but presented with different phenotypes. This work confirms that de novo SMC3 mutations account for ∼ 1%-2% of CdLS-like phenotypes.