Genetic testing in dementia-A medical genetics perspective

Genetic testing in dementia

There is growing public awareness and concern regarding dementia risk. In addition, genetic testing is increasingly accessible and is at the point of being integrated into routine clinical practice. As a result, there is a pressing need for treating clinicians to have the appropriate knowledge base to request and consent for diagnostic genetic testing in cognitive clinics. We outline our approach to genetic testing in patients with Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies and vascular cognitive impairment. We discuss when to consider testing, the consenting process, and the interpretation and communication of genetic test results.

Long-Term Exposure to PM2.5 Constituents, Genetic Susceptibility, and Incident Dementia: A Prospective Cohort Study among 0.2 Million Older Adults

Fine particulate matter, known as PM2.5, is recognized as a risk factor for dementia. However, the specific linkage between PM2.5 constituents and dementia is not well understood. We conducted a cohort of 217,336 participants of the UK Biobank to explore the association of long-term exposure to PM2.5 constituents with all-cause dementia, Alzheimer's disease (AD), and vascular dementia. We estimated PM2.5 constituents based on residential addresses by an evaluation model and used time-varying Cox models and Quantile g-computation models to assess the effects of individual constituents and their mixtures. Genetic susceptibility to dementia was assessed using a polygenic risk score, and its multiplicative and additive interactions with PM2.5 constituents were analyzed. Our results showed that black carbon (BC), ammonium (NH4+), organic matter (OM), and sulfate (SO42-) were positively associated with all-cause dementia, while BC and OM were linked to AD, with BC being the most influential. The combined effect of PM2.5 constituents and genetic risk was stronger than their individual effect. This study offers new insights into the association between PM2.5 constituents and dementia, especially those from fuel combustion and automobile exhaust, and highlights the need for effective prevention strategies.

A survey in Austria supports the significance of genetic counseling and pharmacogenetic testing for mental illness

Introduction

Genetic counseling and testing in psychiatry warrant attention, but research results on attitude, knowledge, personal experience and interest are limited. There are only a few studies that have compared the opinions of the general population and experts regarding genetic counseling and genetic testing in mental illness.

Methods

This study aimed to investigate these gaps through a cross-sectional survey conducted in Austria, involving a sample of the web-active population, representative according to gender, age and geographical location (n=1,000, 24.5% of them had a psychiatric diagnosis), and experts (n=145, 83.4% of them psychiatrists). Two questionnaires were developed. Pearson chi-square statistics were used to compare responses, and regression analyses were employed to measure the strength of psycho-sociodemographic influences on answers.

Results

The findings revealed that public considered genetic counseling to be more important than experts did (68.8% versus 54.2%; Pearson chi-square 12.183; df=1; p<0.001). The general population believed that genetic testing is useful for diagnosing mental disorders, which contrasted with experts' opinions (67.9% versus 17.2%; Pearson chi-square 137.236; df=1; p<0.001). Both groups agreed on the potential benefits of pharmacogenetic testing (79% versus 80%). A small number of individuals from the public had sought genetic counseling (8%), and only a minority of experts had specific training and experience in this field (28%).

Discussion

This is the first survey study on the topic conducted in Austria, with limited international studies available. Austrian experts place less value on genetic counseling compared to their counterparts in other countries. Despite recognized importance placed on genetic counseling and testing, utilization rates remain low. The value of pharmacogenetics is predicted to increase in the future. Consequently, it is crucial for medical training programs to emphasize the significance of genetic counseling and enhance the understanding of genetic aspects related to mental illnesses to enable experts to provide adequate psychoeducation and personalized care to the extent possible to patients and their families.

Clinical application of whole genome sequencing in young onset dementia: challenges and opportunities

INTRODUCTION

Young onset dementia (YOD) by its nature is difficult to diagnose. Despite involvement of multidisciplinary neurogenetics services, patients with YOD and their families face significant diagnostic delays. Genetic testing for people with YOD currently involves a staggered, iterative approach. There is currently no optimal single genetic investigation that simultaneously identifies the different genetic variants resulting in YOD.

AREAS COVERED

This review discusses the advances in clinical genomic testing for people with YOD. Whole genome sequencing (WGS) can be employed as a 'one stop shop' genomic test for YOD. In addition to single nucleotide variants, WGS can reliably detect structural variants, short tandem repeat expansions, mitochondrial genetic variants as well as capture single nucleotide polymorphisms for the calculation of polygenic risk scores.

EXPERT OPINION

WGS, when used as the initial genetic test, can enhance the likelihood of a precision diagnosis and curtail the time taken to reach this. Finding a clinical diagnosis using WGS can reduce invasive and expensive investigations and could be cost effective. These advances need to be balanced against the limitations of the technology and the genetic counseling needs for these vulnerable patients and their families.

Atypical Neuropsychiatric Presentation of FTD-ALS Caused by a Pathogenic Repeat Expansion in C9orf72: A Case Report

The case report describes the presentation of a 42-year-old male ultimately diagnosed with FTD-ALS caused by a genetic mutation, who initially presented with atypical psychiatric symptoms. Given that the initial clinical manifestations of FTD-ALS can be quite variable, the diagnosis is often challenging; the case report aims to highlight several key considerations in the diagnostic assessment, including genetic testing in order to guide clinicians in more timely diagnosis and ultimately improve patient care.

Genetic testing in adults with neurologic disorders: indications, approach, and clinical impacts

The role of genetic testing in neurologic clinical practice has increased dramatically in recent years, driven by research on genetic causes of neurologic disease and increased availability of genetic sequencing technology. Genetic testing is now indicated for adults with a wide range of common neurologic conditions. The potential clinical impacts of a genetic diagnosis are also rapidly expanding, with a growing list of gene-specific treatments and clinical trials, in addition to important implications for prognosis, surveillance, family planning, and diagnostic closure. The goals of this review are to provide practical guidance for clinicians about the role of genetics in their practice and to provide the neuroscience research community with a broad survey of current progress in this field. We aim to answer three questions for the neurologist in practice: Which of my patients need genetic testing? What testing should I order? And how will genetic testing help my patient? We focus on common neurologic disorders and presentations to the neurology clinic. For each condition, we review the most current guidelines and evidence regarding indications for genetic testing, expected diagnostic yield, and recommended testing approach. We also focus on clinical impacts of genetic diagnoses, highlighting a number of gene-specific therapies recently approved for clinical use, and a rapidly expanding landscape of gene-specific clinical trials, many using novel nucleotide-based therapeutic modalities like antisense oligonucleotides and gene transfer. We anticipate that more widespread use of genetic testing will help advance therapeutic development and improve the care, and outcomes, of patients with neurologic conditions.

Presenilin Gene Mutation-associated Psychosis: Phenotypic Characteristics and Clinical Implications

Although psychotic symptoms have been described in association with rare presenilin ( PSEN ) gene mutations underlying early-onset Alzheimer disease (AD), no contemporary reviews on this topic exist. The purpose of this review is to characterize the psychiatric phenotype (specifically with respect to psychosis) of PSEN1 and PSEN2 variant-associated AD. A PubMed search was completed in July 2023. Only articles that described individuals harboring a PSEN1 or PSEN2 mutation who experienced symptoms of psychosis were included in the review. Thirty-three articles describing 52 individuals were included in the review, as well as one other study that provided limited information pertaining to an additional 21 cases. While visual hallucinations were the most common psychotic symptom, followed by persecutory delusions, auditory hallucinations occurred in ~17% of individuals. In ~33% of the reviewed cases psychotic symptoms were present at or near disease onset, and 9 of these individuals experienced auditory hallucinations and/or delusions in the absence of visual hallucinations (~17% of all cases). In many cases, symptoms developed at a relatively young age. As presenilin gene variant-associated psychosis may resemble a primary psychotic disorder, clinicians should be vigilant with respect to screening for signs/symptoms suggestive of neurodegeneration in first-episode psychosis.

Family Communication about Diagnostic Genetic Testing for Younger-Onset Dementia

Younger-onset dementia (YOD) refers to onset before 65 years of age and may be associated with a genetic cause. Family communication surrounding any genetic risk is complex, and this process may be further complicated in a YOD context due to its effects on cognition, behaviour, and associated psychosocial consequences. This study aimed to investigate how individuals experience family communication about potential genetic risk and testing for YOD. Thematic analysis was performed on verbatim transcripts of nine semi-structured interviews undertaken with family members who attended a neurogenetics clinic due to a relative diagnosed with YOD. The interviews explored the participants’ experiences of learning that YOD might be inherited and the ensuing family communication about genetic testing. Four key themes emerged: (1) a clinical diagnostic odyssey was common and could be a motivator for genomic testing, (2) pre-existing family tension and/or disconnection was a common barrier, (3) family members’ autonomy was considered, and (4) avoidant coping strategies influenced communication. Communication regarding potential YOD genetic risk is a complicated process and may be influenced by pre-existing family dynamics, individual coping mechanisms, and a desire to promote autonomy in relatives. To promote effective risk communication, genetic counsellors should pre-emptively address family tensions that may be exacerbated in the context of genetic testing for YOD, with awareness that family strain during a preceding period of diagnostic odyssey is common. Genetic counsellors can offer psychosocial support to facilitate coping with this tension in an adaptive way. The findings also indicated the importance of extending genetic counselling support to relatives.

Young-onset dementia diagnosis, management and care: a narrative review

Young-onset dementia comprises a heterogeneous range of dementias, with onset at less than 65 years of age. These include primary dementias such as Alzheimer disease, frontotemporal and vascular dementias; genetic/familial dementias; metabolic disorders; and secondary dementias such as those that result from alcohol use disorder, traumatic brain injury, and infections. The presentation of young-onset dementia is varied and may include cognitive, psychiatric and neurological symptoms. Diagnostic delay is common, with a frequent diagnostic conundrum being, "Is this young-onset dementia or is this psychiatric?". For assessment and accurate diagnosis, a thorough screen is recommended, such as collateral history and investigations such as neuroimaging, lumbar puncture, neuropsychology, and genetic testing. The management of young-onset dementia needs to be age-appropriate and multidisciplinary, with timely access to services and consideration of the family (including children).

Young-onset dementia: A systematic review of the psychological and social impact on relatives

OBJECTIVE

Young-onset dementia (YOD) has significant impact for the affected person, but also has far-reaching effects on the family. Additionally, biological relatives have an increased genetic risk of developing the condition themselves. This review aimed to identify the psychological and social impacts of YOD in the family, for asymptomatic relatives.

METHODS

A systematic review of key databases for empirical studies about the lived experience of biological relatives at risk for YOD was performed. Data was collated and interpreted via narrative synthesis.

RESULTS

The majority of the nineteen included studies were qualitative and explored the experiences of children with a parent with YOD. Five themes were developed: (1) Onset of YOD disrupts family functioning (2) Emotional impact is significant and varied (3) Uncertain future (due to uncertainty of diagnosis, care-giving responsibilities, and their own increased genetic risk) (4) Lack of visibility in health care and society (5) Coping strategies include physical/cognitive distancing, and emotion-focused coping.

CONCLUSION

Our findings demonstrate a diagnosis of YOD significantly impacts the lives of relatives, yet their experiences and needs often go unnoticed.

PRACTICE IMPLICATIONS

We present a practical framework of questions and strategies for care of relatives, mapped to the self-regulation model of genetic counselling.

Clinical impact of whole-genome sequencing in patients with early-onset dementia

BACKGROUND

In the clinical setting, identification of the genetic cause in patients with early-onset dementia (EOD) is challenging due to multiple types of genetic tests required to arrive at a diagnosis. Whole-genome sequencing (WGS) has the potential to serve as a single diagnostic platform, due to its superior ability to detect common, rare and structural genetic variation.

METHODS

WGS analysis was performed in 50 patients with EOD. Point mutations, small insertions/deletions, as well as structural variants (SVs) and short tandem repeats (STRs), were analysed. An Alzheimer's disease (AD)-related polygenic risk score (PRS) was calculated in patients with AD.

RESULTS

Clinical genetic diagnosis was achieved in 7 of 50 (14%) of the patients, with a further 8 patients (16%) found to have established risk factors which may have contributed to their EOD. Two pathogenic variants were identified through SV analysis. No expanded STRs were found in this study cohort, but a blinded analysis with a positive control identified a C9orf72 expansion accurately. Approximately 37% (7 of 19) of patients with AD had a PRS equivalent to >90th percentile risk.

DISCUSSION

WGS acts as a single genetic test to identify different types of clinically relevant genetic variations in patients with EOD. WGS, if used as a first-line clinical diagnostic test, has the potential to increase the diagnostic yield and reduce time to diagnosis for EOD.