Expanding ACMG variant classification guidelines into a general framework

Accelerating genetic diagnostics in retinitis pigmentosa: implementation of a semi-automated bespoke cohort analysis workflow for Hong Kong Genome Project

The study aims to enhance the efficiency of the genetic variant curation process at the Hong Kong Genome Institute by developing a Semi-Automated Bespoke Cohort Analysis Workflow (S-BCAW) for patients with, or suspected to have, retinitis pigmentosa (RP) in the Hong Kong Genome Project (HKGP), leveraging advances in next-generation sequencing (NGS). A comparative analysis involving 79 RP patients was conducted using both the conventional manual workflow and the novel S-BCAW, which integrates initial filtering and variant classification based on ACMG guidelines, followed by detailed manual review. The diagnostic yields from both methods were identical, but the bespoke workflow reduced analysis time by approximately 60% (1.5 h/sample). This efficiency increase resulted from automated application of ACMG rules and systematic aggregation of supportive data, including disease-specific information. The study reports 25 positive cases with a diagnostic yield of 32%, including three novel variants. The S-BCAW significantly improves efficiency, helping to end the diagnostic odyssey for patients in the HKGP. This approach facilitates rapid assessment of variant pathogenicity, enhancing the feasibility and timeliness of NGS technology for clinical applications, especially in urgent scenarios.

Genetics and clinical implications of SPINK1 in the pancreatitis continuum and pancreatic cancer

Serine peptidase inhibitor, Kazal type 1 (SPINK1), a 56-amino-acid protein in its mature form, was among the first pancreatic enzymes to be extensively characterized biochemically and functionally. Synthesized primarily in pancreatic acinar cells and traditionally known as pancreatic secretory trypsin inhibitor, SPINK1 protects the pancreas by inhibiting prematurely activated trypsin. Since 2000, interest in SPINK1 has resurged following the discovery of genetic variants linked to chronic pancreatitis (CP). This review provides a historical overview of SPINK1's discovery, function, and gene structure before examining key genetic findings. We highlight three variants with well-characterized pathogenic mechanisms: c.-4141G > T, a causative enhancer variant linked to the extensively studied p.Asn34Ser (c.101A > G), which disrupts a PTF1L-binding site within an evolutionarily conserved HNF1A-PTF1L cis-regulatory module; c.194 + 2T > C, a canonical 5' splice site GT > GC variant that retains 10% of wild-type transcript production; and an Alu insertion in the 3'-untranslated region, which causes complete loss of function by forming extended double-stranded RNA structures with pre-existing Alu elements in deep intronic regions. We emphasize the integration of a full-length gene splicing assay (FLGSA) with SpliceAI's predictive capabilities, establishing SPINK1 the first disease gene for which the splicing impact of all possible coding variants was prospectively determined. Findings from both mouse models and genetic association studies support the sentinel acute pancreatitis event (SAPE) model, which explains the progression from acute pancreatitis to CP. Additionally, SPINK1 variants may contribute to an increased risk of pancreatic ductal adenocarcinoma (PDAC). Finally, we discuss the therapeutic potential of SPINK1, particularly through adeno-associated virus type 8 (AAV8)-mediated overexpression of SPINK1 as a strategy for treating and preventing pancreatitis, and highlight key areas for future research.

Inherited retinal degeneration in Malay and Indian populations of Singapore and Malaysia: a prospective multicentre study

PURPOSE

To analyze the phenotypic and genotypic characteristics of inherited retinal degeneration (IRD) patients of Malay and Indian ethnicity from Singapore and Malaysia.

METHODS

Ethnic Malay and Indian IRD patients were consecutively enrolled from retina clinics in Singapore and Malaysia. Phenotypic and genetic data were reviewed.

RESULTS

A total of 100 unrelated individuals (Malay: n = 46, Indian: n = 54) were enrolled. Sixteen distinct IRD phenotypes were identified, with nonsyndromic retinitis pigmentosa (RP) comprising 46% of all cases. Stargardt disease and cone-rod dystrophy accounted for 20% and 11% of cases, respectively. Exome sequencing yielded genotypes in 64.3% of Malay and 68.9% of Indian cases. Variants in ABCA4 were the most common cause of IRD overall. Recurrent variants were identified in ABCA4, GUCY2D, PRPH2, and TULP1 for Malays, and in ABCA4 and MFSD8 (CLN7) for Indians. Homozygosity was more frequent among Indians than Malays (58.1% vs. 19.2%; p = 0.003).

CONCLUSIONS

This study demonstrated diverse phenotypic and genotypic outcomes in Malay and Indian populations of Singapore and Malaysia, with distinct differences between them. Homozygosity was common among ethnic Indian IRD cases, explaining phenotypic diversity. These findings inform the identification of regionally relevant IRDs for developing targeted therapies in Malay and Indian patients from Southeast Asia.

The mutational landscape of ARMC5 in Primary Bilateral Macronodular Adrenal Hyperplasia: an update

BACKGROUND

Primary Bilateral Macronodular Adrenal Hyperplasia (PBMAH) is a rare cause of Cushing's syndrome due to bilateral adrenocortical macronodules. Germline inactivating variants of the tumor suppressor gene ARMC5 are responsible for 20-25% of apparently sporadic PBMAH cases and 80% of familial presentations. ARMC5 screening is now routinely performed for PBMAH patients and families. Based on literature review and own observation, this study aims to give an overview of both published and unpublished ARMC5 genetic alterations and to compile the available evidence to discriminate pathogenic from benign variants.

RESULTS

146 different germline variants (110 previously published and 36 novel) are identified, including 46% missense substitutions, 45% truncating variants, 3% affecting splice sites, 4% in-frame variants and 2% large deletions. In addition to the germline events, somatic 16p loss-of-heterozygosity and 104 different somatic events are described. The pathogenicity of ARMC5 variants is established on the basis of their frequency in the general population, in silico predictions, familial segregation and tumor DNA sequencing.

CONCLUSIONS

This is the first extensive review of ARMC5 pathogenic variants. It shows that they are spread on the whole coding sequence. This is a valuable resource for genetic investigations of PBMAH and will help the interpretation of new missense substitutions that are continuously identified.

Hemoglobin Variants as Targets for Stabilizing Drugs

Hemoglobin is an oxygen-transport protein in red blood cells that interacts with multiple ligands, e.g., oxygen, carbon dioxide, carbon monoxide, and nitric oxide. Genetic variations in hemoglobin chains, such as those underlying sickle cell disease and thalassemias, present substantial clinical challenges. Here, we review the progress in research, including the use of allosteric modulators, pharmacological chaperones, and antioxidant treatments, which has begun to improve hemoglobin stability and oxygen affinity. According to UniProt (as of 7 August 2024), 819 variants of the α-hemoglobin subunit and 771 variants of the β-hemoglobin subunit have been documented, with over 116 classified as unstable. These data demonstrate the urgent need to develop variant-specific stabilizing options. Beyond small-molecule drugs/binders, novel protein-based strategies-such as engineered hemoglobin-binding proteins (including falcilysin, llama-derived nanobodies, and α-hemoglobin-stabilizing proteins)-offer promising new options. As our understanding of hemoglobin's structural and functional diversity grows, so does the potential for genotype-driven approaches. Continued research into hemoglobin stabilization and ligand-binding modification may yield more precise, effective treatments and pave the way toward effective strategies for hemoglobinopathies.

Monogenic lupus with neuroregression in an infant due to rare compound heterozygous variants in C1QA gene: Case-based review

Monogenic lupus is a rare variant of systemic lupus erythematosus (SLE) that develops in patients with a single gene disorder. Early complement component deficiencies were the first forms of monogenic lupus to be described, and C1Q gene mutations are one of the most common forms. C1QA complement deficiency has been reported to occur usually due to biallelic variants in C1QA gene, and compound heterozygous variants in C1QA gene have rarely been reported. A majority of monogenic lupus patients with C1Q deficiency present with mucocutaneous, renal, and musculoskeletal manifestations. Our patient is an unusual case of monogenic lupus with severe neurological manifestations along with cutaneous, haematological, and hepatic manifestations secondary to rare compound heterozygous variants in C1QA gene and antiribosomal P autoantibody positivity. She was treated with glucocorticoids, rituximab, and fresh frozen plasma with partial neurological recovery. Thus, we present a unique case of monogenic lupus due to a rare compound heterozygous variant in C1QA gene with a brief review of literature.

Clinically Significant BRCA1 and BRCA2 Germline Variants in Breast Cancer-A Single-Center Experience

BACKGROUND

Conditions associated with BRCA1/2 pathogenic (PVs) or likely pathogenic variants (LPVs) are often severe. The early detection of carrier status is ideal, as it provides options for effective case management.

MATERIALS AND METHODS

The study involved 58 patients with a personal and familial history of breast cancer (BC) who underwent genetic testing at the Regional Centre for Medical Genetics Dolj over a three-year period. An immunohistochemical panel (HER2, ER, PR, and Ki-67) was used to define the molecular subtypes of breast tumors. The AmpliSeq for Illumina BRCA Panel was used to evaluate germline variants in the BRCA1 and BRCA2 genes in patients with BC. The χ2 test and Fisher's exact test were used to compare the different parameters studied.

RESULTS

Our findings revealed that 15.5% of the patients carried either BRCA1 or BRCA2 PVs or LPVs. BRCA1 carriers had aggressive tumors whereas BRCA2 carriers had rather low-grade tumors.

CONCLUSIONS

The study revealed that PVs in both BRCA genes have a significant frequency among BC patients in our region, and BRCA1 carriers tend to develop more aggressive tumors than carriers of BRCA2 PVs and patients with no germline PVs in either of the two genes. These observations could provide new epidemiologic data for this disease in our region and contribute further to the development of national screening strategies.

Refining the interpretation of variants of uncertain significance in hereditary cancer screening through integrated RNA sequencing

Purpose

Although up to 25% of germline variants are predicted to affect splicing, most are classified as variants of uncertain significance (VUS) because of the limited understanding of their functional consequences. Here, we investigated the impact of RNA sequencing (RNA-seq) data on the ability to resolve splicing-related VUS.

Methods

Patients with VUS predicted to alter splicing identified through commercial hereditary cancer testing between October 2021 to July 2023 were included. RNA-seq was used to compare splicing patterns between patient blood samples and normal controls. VUS reclassification rates were calculated.

Results

In total, 411 VUS in 52 genes predicted to affect splicing were included. RNA-seq results resolved 26.3% (108/411) of the VUS: 28 (6.8%) upgraded to pathogenic/likely pathogenic, and 80 (19.5%) downgraded to not reportable. Among the 28 upgraded, 17 (60.7%) were intronic, 9 (32.1%) were exonic missense variants, and 2 (7.1%) were exonic synonymous variants. Most of the VUS downgraded to not reportable were intronic (64/80, 80%). The remaining 16 (20%) of the downgraded VUS were synonymous variants.

Conclusion

This study underscores the utility of RNA-seq to detect variants that affect splicing and could have an impact on cancer risk assessment management and treatment.

Good laboratory practice for PGT-M: Turkish Society of Reproductive Medicine guidelines

This guideline was prepared by the Turkish Society of Reproductive Medicine to define the conditions and requirements for an outsourced preimplantation genetic testing (PGT) programme in line with the experience and needs of practitioners. This guideline is intended to be a reference document for assisted reproductive technology centres, genetic diagnosis centres, non-governmental organizations working on reproductive health, legal experts, consultants working on laboratory accreditation, academicians specializing in ethical issues, and policy makers. The Consortium aims to provide recommendations addressing the challenges of genetic testing, especially PGT for monogenic diseases (PGT-M) due to the high rate of consanguineous marriage in Turkey. For this purpose, this summary document specifically includes challenges and recommendations regarding PGT-M practice, and aims to identify and aid in prevention of errors leading to misdiagnosis. The recommendations can be modified to fit other locations.

Assessing the Utility of ColabFold and AlphaMissense in Determining Missense Variant Pathogenicity for Congenital Myasthenic Syndromes

BACKGROUND/OBJECTIVES

Congenital myasthenic syndromes (CMSs) are caused by variants in >30 genes with increasing numbers of variants of unknown significance (VUS) discovered by next-generation sequencing. Establishing VUS pathogenicity requires in vitro studies that slow diagnosis and treatment initiation. The recently developed protein structure prediction software AlphaFold2/ColabFold has revolutionized structural biology; such predictions have also been leveraged in AlphaMissense, which predicts ClinVar variant pathogenicity with 90% accuracy. Few reports, however, have tested these tools on rigorously characterized clinical data. We therefore assessed ColabFold and AlphaMissense as diagnostic aids for CMSs, using variants of the CHRN genes that encode the nicotinic acetylcholine receptor (nAChR).

METHODS

Utilizing a dataset of 61 clinically validated CHRN variants, (1) we evaluated the possibility of a ColabFold metric (either predicted structural disruption, prediction confidence, or prediction quality) that distinguishes variant pathogenicity; (2) we assessed AlphaMissense's ability to differentiate variant pathogenicity; and (3) we compared AlphaMissense to the existing pathogenicity prediction programs AlamutVP and EVE.

RESULTS

Analyzing the variant effects on ColabFold CHRN structure prediction, prediction confidence, and prediction quality did not yield any reliable pathogenicity indicative metric. However, AlphaMissense predicted variant pathogenicity with 63.93% accuracy in our dataset-a much greater proportion than AlamutVP (27.87%) and EVE (28.33%).

CONCLUSIONS

Emerging in silico tools can revolutionize genetic disease diagnosis-however, improvement, refinement, and clinical validation are imperative prior to practical acquisition.

Alu insertion-mediated dsRNA structure formation with pre-existing Alu elements as a disease-causing mechanism

We previously identified a homozygous Alu insertion variant (Alu_Ins) in the 3'-untranslated region (3'-UTR) of SPINK1 as the cause of severe infantile isolated exocrine pancreatic insufficiency. Although we established that Alu_Ins leads to the complete loss of SPINK1 mRNA expression, the precise mechanisms remained elusive. Here, we aimed to elucidate these mechanisms through a hypothesis-driven approach. Initially, we speculated that, owing to its particular location, Alu_Ins could independently disrupt mRNA 3' end formation and/or affect other post-transcriptional processes such as nuclear export and translation. However, employing a 3'-UTR luciferase reporter assay, Alu_Ins was found to result in only an ∼50% reduction in luciferase activity compared to wild type, which is insufficient to account for the severe pancreatic deficiency in the Alu_Ins homozygote. We then postulated that double-stranded RNA (dsRNA) structures formed between Alu elements, an upstream mechanism regulating gene expression, might be responsible. Using RepeatMasker, we identified two Alu elements within SPINK1's third intron, both oriented oppositely to Alu_Ins. Through RNAfold predictions and full-length gene expression assays, we investigated orientation-dependent interactions between these Alu repeats. We provide compelling evidence to link the detrimental effect of Alu_Ins to extensive dsRNA structures formed between Alu_Ins and pre-existing intronic Alu sequences, including the restoration of SPINK1 mRNA expression by aligning all three Alu elements in the same orientation. Given the widespread presence of Alu elements in the human genome and the potential for new Alu insertions at almost any locus, our findings have important implications for detecting and interpreting Alu insertions in disease genes.

A brief clinical genetics review: stepwise diagnostic processes of a monogenic disorder-hypertriglyceridemia

The completion of the Human Genome Project and tremendous advances in automated high-throughput genetic analysis technologies have enabled explosive progress in the field of genetics, which resulted in countless discoveries of novel genes and pathways. Many phenotype- or disease-associated single nucleotide polymorphisms (SNPs) with a high statistical significance have been identified through numerous genome-wide association studies (GWAS), and various polygenic risk scoring (PRS) schemes have been proposed to identify individuals with a high risk for a certain trait or disorder. Meanwhile, medical education in genetics has lagged far behind, leaving many physicians and healthcare providers unprepared in the genomic era. Thus, there is an urgent need to educate physicians and healthcare providers with basic knowledge and skills in genetics. To facilitate this, some basic terminologies and concepts are discussed in this review. In addition, some important considerations in delineating and incorporating clinical genetic testing in the diagnosis and management of a monogenic disorder are illustrated in a stepwise fashion. Furthermore, the effects of disease-associated SNPs represented by a PRS scheme clearly demonstrated that even the phenotypes of a monogenic disorder due to the same pathogenic variant in family members are modulated by the polygenic background. In human genetics, despite these explosive advancements, we are still far from clearly deciphering the interplay of gene variants to effect unique characteristics in an individual. In addition, sophisticated genome or gene directed therapies are being investigated for numerous disorders. Therefore, evolution in the field of genetics is likely to continue into the foreseeable future. In the meantime, much emphasis should be placed on educating physicians and healthcare professionals to be well-versed and skillful in the clinical use of genetics so that they can fully embrace the new era of precision medicine.

The co-occurrence of genetic variants in the TYR and OCA2 genes confers susceptibility to albinism

Although rare genetic conditions are mostly caused by DNA sequence alterations that functionally disrupt individual genes, large-scale studies using genome sequencing have started to unmask additional complexity. Understanding how combinations of variants in different genes shape human phenotypes is expected to provide important insights into the clinical and genetic heterogeneity of rare disorders. Here, we use albinism, an archetypal rare condition associated with hypopigmentation, as an exemplar for the study of genetic interactions. We analyse data from the Genomics England 100,000 Genomes Project alongside a cohort of 1120 individuals with albinism, and investigate the effect of dual heterozygosity for the combination of two established albinism-related variants: TYR:c.1205 G > A (p.Arg402Gln) [rs1126809] and OCA2:c.1327 G > A (p.Val443Ile) [rs74653330]. As each of these changes alone is insufficient to cause disease when present in the heterozygous state, we sought evidence of synergistic effects. We show that, when both variants are present, the probability of receiving a diagnosis of albinism is significantly increased (odds ratio 12.8; 95% confidence interval 6.0 - 24.7; p-value 2.1 ×10-8). Further analyses in an independent cohort, the UK Biobank, support this finding and highlight that heterozygosity for the TYR:c.1205 G > A and OCA2:c.1327 G > A variant combination is associated with statistically significant alterations in visual acuity and central retinal thickness (traits that are considered albinism endophenotypes). The approach discussed in this report opens up new avenues for the investigation of oligogenic patterns in apparently Mendelian disorders.

Estimation of demography and mutation rates from one million haploid genomes

As genetic sequencing costs have plummeted, datasets with sizes previously un-thinkable have begun to appear. Such datasets present new opportunities to learn about evolutionary history, particularly via rare alleles that record the very recent past. However, beyond the computational challenges inherent in the analysis of many large-scale datasets, large population-genetic datasets present theoretical problems. In particular, the majority of population-genetic tools require the assumption that each mutant allele in the sample is the result of a single mutation (the "infinite sites" assumption), which is violated in large samples. Here, we present DR EVIL, a method for estimating mutation rates and recent demographic history from very large samples. DR EVIL avoids the infinite-sites assumption by using a diffusion approximation to a branching-process model with recurrent mutation. The branching-process approach limits the method to rare alleles, but, along with recent results, renders tractable likelihoods with recurrent mutation. We show that DR EVIL performs well in simulations and apply it to rare-variant data from a million haploid samples, identifying a signal of mutation-rate heterogeneity within commonly analyzed classes and predicting that in modern sample sizes, most rare variants at sites with high mutation rates represent the descendants of multiple mutation events.

Comparison of the ABC and ACMG systems for variant classification

The ABC and ACMG variant classification systems were compared by asking mainly European clinical laboratories to classify variants in 10 challenging cases using both systems, and to state if the variant in question would be reported as a relevant result or not as a measure of clinical utility. In contrast to the ABC system, the ACMG system was not made to guide variant reporting but to determine the likelihood of pathogenicity. Nevertheless, this comparison is justified since the ACMG class determines variant reporting in many laboratories. Forty-three laboratories participated in the survey. In seven cases, the classification system used did not influence the reporting likelihood when variants labeled as "maybe report" after ACMG-based classification were included. In three cases of population frequent but disease-associated variants, there was a difference in favor of reporting after ABC classification. A possible reason is that ABC step C (standard variant comments) allows a variant to be reported in one clinical setting but not another, e.g., based on Bayesian-based likelihood calculation of clinical relevance. Finally, the selection of ACMG criteria was compared between 36 laboratories. When excluding criteria used by less than four laboratories (<10%), the average concordance rate was 46%. Taken together, ABC-based classification is more clear-cut than ACMG-based classification since molecular and clinical information is handled separately, and variant reporting can be adapted to the clinical question and phenotype. Furthermore, variants do not get a clinically inappropriate label, like pathogenic when not pathogenic in a clinical context, or variant of unknown significance when the significance is known.

The Importance of Molecular Genetic Testing for Precision Diagnostics, Management, and Genetic Counseling in MODY Patients

Maturity-onset diabetes of the young (MODY) is part of the heterogeneous group of monogenic diabetes (MD) characterized by the non-immune dysfunction of pancreatic β-cells. The diagnosis of MODY still remains a challenge for clinicians, with many cases being misdiagnosed as type 1 or type 2 diabetes mellitus (T1DM/T2DM), and over 80% of cases remaining undiagnosed. With the introduction of modern technologies, important progress has been made in deciphering the molecular mechanisms and heterogeneous etiology of MD, including MODY. The aim of our study was to identify genetic variants associated with MODY in a group of patients with early-onset diabetes/prediabetes in whom a form of MD was clinically suspected. Genetic testing, based on next-generation sequencing (NGS) technology, was carried out either in a targeted manner, using gene panels for monogenic diabetes, or by analyzing the entire exome (whole-exome sequencing). GKC-MODY 2 was the most frequently detected variant, but rare forms of KCNJ11-MODY 13, specifically, HNF4A-MODY 1, were also identified. We have emphasized the importance of genetic testing for early diagnosis, MODY subtype differentiation, and genetic counseling. We presented the genotype-phenotype correlations, especially related to the clinical evolution and personalized therapy, also emphasizing the particularities of each patient in the family context.

ECFS standards of care on CFTR-related disorders: Towards a comprehensive program for affected individuals

After three publications defining an updated guidance on the diagnostic criteria for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (pwCFTR-RDs), establishing its relationship to CFTR-dysfunction and describing the individual disorders, this fourth and last paper in the series addresses some critical challenges facing health care providers and pwCFTR-RD. Topics included are: 1) benefits and obstacles to collect data from pwCFTR-RD are discussed, together with the opportunity to integrate them into established CF-registries; 2) the potential of infants designated CRMS/CFSPID to develop a CFTR-RD and how to communicate this information; 3) a description of the challenges in genetic counseling, with particular regard to phenotypic variability, unknown long-term evolution, CFTR testing and pregnancy termination 4) a proposal for the assessment of potential barriers to the implementation and dissemination of the produced documents to health care professionals involved in the care of pwCFTR-RD and a process to monitor the implementation of the CFTR-RD recommendations; 5) clinical trials investigating the efficacy of CFTR modulators in CFTR-RD and how endpoints and outcomes might be adapted to the heterogeneity of these disorders.

Significant but partial lipoprotein lipase functional loss caused by a novel occurrence of rare LPL biallelic variants

BACKGROUND

Lipoprotein lipase (LPL) plays a crucial role in triglyceride hydrolysis. Rare biallelic variants in the LPL gene leading to complete or near-complete loss of function cause autosomal recessive familial chylomicronemia syndrome. However, rare biallelic LPL variants resulting in significant but partial loss of function are rarely documented. This study reports a novel occurrence of such rare biallelic LPL variants in a Chinese patient with hypertriglyceridemia-induced acute pancreatitis (HTG-AP) during pregnancy and provides an in-depth functional characterization.

METHODS

The complete coding sequences and adjacent intronic regions of the LPL, APOC2, APOA5, LMF1, and GPIHBP1 genes were analyzed by Sanger sequencing. The aim was to identify rare variants, including nonsense, frameshift, missense, small in-frame deletions or insertions, and canonical splice site mutations. The functional impact of identified LPL missense variants on protein expression, secretion, and activity was assessed in HEK293T cells through single and co-transfection experiments, with and without heparin treatment.

RESULTS

Two rare LPL missense variants were identified in the patient: the previously reported c.809G > A (p.Arg270His) and a novel c.331G > C (p.Val111Leu). Genetic testing confirmed these variants were inherited biallelically. Functional analysis showed that the p.Arg270His variant resulted in a near-complete loss of LPL function due to effects on protein synthesis/stability, secretion, and enzymatic activity. In contrast, the p.Val111Leu variant retained approximately 32.3% of wild-type activity, without impacting protein synthesis, stability, or secretion. Co-transfection experiments indicated a combined activity level of 20.7%, suggesting no dominant negative interaction between the variants. The patient's post-heparin plasma LPL activity was about 35% of control levels.

CONCLUSIONS

This study presents a novel case of partial but significant loss-of-function biallelic LPL variants in a patient with HTG-AP during pregnancy. Our findings enhance the understanding of the nuanced relationship between LPL genotypes and clinical phenotypes, highlighting the importance of residual LPL function in disease manifestation and severity. Additionally, our study underscores the challenges in classifying partial loss-of-function variants in classical Mendelian disease genes according to the American College of Medical Genetics and Genomics (ACMG)'s variant classification guidelines.

Copy-number variants in the ACMG secondary finding genes: A reporting framework for clinical cytogeneticists

Purpose

To determine the pathogenicity and frequency of copy-number variants (CNV) in the 81 secondary finding (SFv3.2) genes recommended by the American College of Medical Genetics and Genomics (ACMG).

Methods

Review of published evidence on pathogenicity of partial or complete copy-number losses or gains in ACMG SFv3.2 was performed. Frequency of reportable CNVs in the ACMG SFv3.2 genes was investigated among 10,959 patients tested by chromosomal microarray analysis in a single academic testing laboratory at the University of Pittsburgh Medical Center during 2011 to 2023.

Results

We identified 58 ACMG SFv3.2 genes for which sufficient evidence supports reporting of partial or complete copy-number losses as secondary findings. On the contrary, reporting of copy-number gains was not supported by evidence in any of the ACMG SFv3.2 genes. Overall, CNVs in SFv3.2 genes were detected in 32 of 10,959 (0.29% or 1 in 343) patients in our cohort.

Conclusion

This study provides a framework for consistent reporting of CNVs, detected by chromosomal microarray analysis, exome, or genome sequencing, in any of the ACMG SFv3.2 genes. To our knowledge, this is the largest cohort of patients studied for estimation of frequency of reportable CNVs in the ACMG SFv3.2 genes.

Recommendations for risk allele evidence curation, classification, and reporting from the ClinGen Low Penetrance/Risk Allele Working Group

PURPOSE

Genetic variants at the low end of the penetrance spectrum have historically been challenging to interpret because their high population frequencies exceed the disease prevalence of the associated condition, leading to a lack of clear segregation between the variant and disease. There is currently substantial variation in the classification of these variants, and no formal classification framework has been widely adopted. The Clinical Genome Resource Low Penetrance/Risk Allele Working Group was formed to address these challenges and promote harmonization within the clinical community.

METHODS

The work presented here is the product of internal and community Likert-scaled surveys in combination with expert consensus within the Working Group.

RESULTS

We formally recognize risk alleles and low-penetrance variants as distinct variant classes from those causing highly penetrant disease that require special considerations regarding their clinical classification and reporting. First, we provide a preferred terminology for these variants. Second, we focus on risk alleles and detail considerations for reviewing relevant studies and present a framework for the classification these variants. Finally, we discuss considerations for clinical reporting of risk alleles.

CONCLUSION

These recommendations support harmonized interpretation, classification, and reporting of variants at the low end of the penetrance spectrum.

Combining full-length gene assay and SpliceAI to interpret the splicing impact of all possible SPINK1 coding variants

BACKGROUND

Single-nucleotide variants (SNVs) within gene coding sequences can significantly impact pre-mRNA splicing, bearing profound implications for pathogenic mechanisms and precision medicine. In this study, we aim to harness the well-established full-length gene splicing assay (FLGSA) in conjunction with SpliceAI to prospectively interpret the splicing effects of all potential coding SNVs within the four-exon SPINK1 gene, a gene associated with chronic pancreatitis.

RESULTS

Our study began with a retrospective analysis of 27 SPINK1 coding SNVs previously assessed using FLGSA, proceeded with a prospective analysis of 35 new FLGSA-tested SPINK1 coding SNVs, followed by data extrapolation, and ended with further validation. In total, we analyzed 67 SPINK1 coding SNVs, which account for 9.3% of the 720 possible coding SNVs. Among these 67 FLGSA-analyzed SNVs, 12 were found to impact splicing. Through detailed comparison of FLGSA results and SpliceAI predictions, we inferred that the remaining 653 untested coding SNVs in the SPINK1 gene are unlikely to significantly affect splicing. Of the 12 splice-altering events, nine produced both normally spliced and aberrantly spliced transcripts, while the remaining three only generated aberrantly spliced transcripts. These splice-impacting SNVs were found solely in exons 1 and 2, notably at the first and/or last coding nucleotides of these exons. Among the 12 splice-altering events, 11 were missense variants (2.17% of 506 potential missense variants), and one was synonymous (0.61% of 164 potential synonymous variants). Notably, adjusting the SpliceAI cut-off to 0.30 instead of the conventional 0.20 would improve specificity without reducing sensitivity.

CONCLUSIONS

By integrating FLGSA with SpliceAI, we have determined that less than 2% (1.67%) of all possible coding SNVs in SPINK1 significantly influence splicing outcomes. Our findings emphasize the critical importance of conducting splicing analysis within the broader genomic sequence context of the study gene and highlight the inherent uncertainties associated with intermediate SpliceAI scores (0.20 to 0.80). This study contributes to the field by being the first to prospectively interpret all potential coding SNVs in a disease-associated gene with a high degree of accuracy, representing a meaningful attempt at shifting from retrospective to prospective variant analysis in the era of exome and genome sequencing.

Whole genome sequencing in clinical practice

Whole genome sequencing (WGS) is becoming the preferred method for molecular genetic diagnosis of rare and unknown diseases and for identification of actionable cancer drivers. Compared to other molecular genetic methods, WGS captures most genomic variation and eliminates the need for sequential genetic testing. Whereas, the laboratory requirements are similar to conventional molecular genetics, the amount of data is large and WGS requires a comprehensive computational and storage infrastructure in order to facilitate data processing within a clinically relevant timeframe. The output of a single WGS analyses is roughly 5 MIO variants and data interpretation involves specialized staff collaborating with the clinical specialists in order to provide standard of care reports. Although the field is continuously refining the standards for variant classification, there are still unresolved issues associated with the clinical application. The review provides an overview of WGS in clinical practice - describing the technology and current applications as well as challenges connected with data processing, interpretation and clinical reporting.

Germline POT1 Variants: A Critical Perspective on POT1 Tumor Predisposition Syndrome

The Protection of Telomere 1 (POT1) gene was identified as a melanoma predisposition candidate nearly 10 years ago. Thereafter, various cancers have been proposed as associated with germline POT1 variants in the context of the so-called POT1 Predisposition Tumor Syndrome (POT1-TPD). While the key role, and related risks, of the alterations in POT1 in melanoma are established, the correlation between germline POT1 variants and the susceptibility to other cancers partially lacks evidence, due also to the rarity of POT1-TPD. Issues range from the absence of functional or segregation studies to biased datasets or the need for a revised classification of variants. Furthermore, a proposal of a surveillance protocol related to the cancers associated with POT1 pathogenic variants requires reliable data to avoid an excessive, possibly unjustified, burden for POT1 variant carriers. We propose a critical perspective regarding data published over the last 10 years that correlate POT1 variants to various types of cancer, other than cutaneous melanoma, to offer food for thought for the specialists who manage cancer predisposition syndromes and to stimulate a debate on the grey areas that have been exposed.

Deep brain stimulation of globus pallidus internus and subthalamic nucleus in Parkinson's disease: a multicenter, retrospective study of efficacy and safety

BACKGROUND

Deep brain stimulation (DBS) is an established therapeutic option in advanced Parkinson's disease (PD). Literature data and recent guidelines remain inconclusive about the best choice as a target between the subthalamic nucleus (STN) and the globus pallidus internus (GPi).

MATERIALS AND METHODS

We retrospectively reviewed the clinical efficacy outcomes of 48 DBS-implanted patients (33 STN-DBS and 15 GPi-DBS) at a short- (<1 year from the surgery) and long-term (2-5 years) follow-up. Also, clinical safety outcomes, including postoperative surgical complications and severe side effects, were collected.

RESULTS

We found no difference between STN-DBS and GPi-DBS in improving motor symptoms at short-term evaluation. However, STN-DBS achieved a more prominent reduction in oral therapy (L-DOPA equivalent daily dose, P = .02). By contrast, GPi-DBS was superior in ameliorating motor fluctuations and dyskinesia (MDS-UPDRS IV, P < .001) as well as motor experiences of daily living (MDS-UPDRS II, P = .03). The greater efficacy of GPi-DBS on motor fluctuations and experiences of daily living was also present at the long-term follow-up. We observed five serious adverse events, including two suicides, all among STN-DBS patients.

CONCLUSION

Both STN-DBS and GPi-DBS are effective in improving motor symptoms severity and complications, but GPi-DBS has a greater impact on motor fluctuations and motor experiences of daily living. These results suggest that the two targets should be considered equivalent in motor efficacy, with GPi-DBS as a valuable option in patients with prominent motor complications. The occurrence of suicides in STN-treated patients claims further attention in target selection.

The VUS Challenge in Cystic Kidney Disease: A Case-Based Review

Genetic testing in nephrology is becoming increasingly important to diagnose patients and to provide appropriate care. This is especially true for autosomal dominant polycystic kidney disease (ADPKD) because this is a common cause of kidney failure and genetically complex. In addition to the major genes, PKD1 and PKD2 , there are at least six minor loci, and phenotypic, and in some cases, genetic overlap with other cystic disorders. Targeted next-generation sequencing, a low-cost, high-throughput technique, has made routine genetic testing viable in nephrology clinics. Appropriate pre- and post-testing genetic counseling is essential to the testing process. Carefully assessing variants is also critical, with the genetic report classifying variants in accordance with American College of Medical Genetics and Genomics guidelines. However, variant of uncertain significance (VUSs) may pose a significant challenge for the ordering clinician. In ADPKD, and particularly within PKD1 , there is high allelic heterogeneity; no single variant is present in more than 2% of families. The Mayo/Polycystic Kidney Disease Foundation variant database, a research tool, is the best current database of PKD1 and PKD2 variants containing over 2300 variants identified in individuals with polycystic kidney disease, but novel variants are often identified. In patients with a high pretest probability of ADPKD on the basis of clinical criteria, but no finding of a pathogenic (P) or likely pathogenic (LP) variant in a cystic kidney gene, additional evaluation of cystic gene VUS can be helpful. In this case-based review, we propose an algorithm for the assessment of such variants in a clinical setting and show how some can be reassigned to a diagnostic grouping. When assessing the relevance of a VUS, we consider both patient/family-specific and allele-related factors using population and variant databases and available prediction tools, as well as genetic expertise. This analysis plus further family studies can aid in making a genetic diagnosis.

Compendium of Clinical Variant Classification for 2,246 Unique ABCA4 Variants to Clarify Variant Pathogenicity in Stargardt Disease Using a Modified ACMG/AMP Framework

Biallelic variants in ABCA4 cause Stargardt disease (STGD1), the most frequent heritable macular disease. Determination of the pathogenicity of variants in ABCA4 proves to be difficult due to (1) the high number of benign and pathogenic variants in the gene; (2) the presence of many rare ABCA4 variants; (3) the presence of complex alleles for which phasing data are absent; (4) the extensive variable expressivity of this disease and (5) reduced penetrance of hypomorphic variants. Therefore, the classification of many variants in ABCA4 is currently of uncertain significance. Here, we complemented the ABCA4 Leiden Open Variation Database (LOVD) with data from ~11,000 probands with ABCA4-associated inherited retinal diseases from literature up to the end of 2020. We carefully adapted the ACMG/AMP classifications to ABCA4 incorporating ClinGen recommendations and assigned these classifications to all 2,246 unique variants from the ABCA4 LOVD to increase the knowledge of pathogenicity. In total, 1,248 variants were categorized with a likely pathogenic or pathogenic classification, whereas 194 variants were categorized with a likely benign or benign classification. This uniform and improved structured reclassification, incorporating the largest dataset of ABCA4-associated retinopathy cases so far, will improve both the diagnosis as well as genetic counselling for individuals with ABCA4-associated retinopathy.

Genetic counseling for pre-implantation genetic testing of monogenic disorders (PGT-M)

Pre-implantation genetic testing (PGT) is a vital tool in preventing chromosomal aneuploidies and other genetic disorders including those that are monogenic in origin. It is performed on embryos created by intracytoplasmic sperm injection (ICSI). Genetic counseling in the area of assisted reproductive technology (ART) has also evolved along with PGT and is considered an essential and integral part of Reproductive Medicine. While PGT has the potential to prevent future progeny from being affected by genetic conditions, genetic counseling helps couples understand and adapt to the medical, psychological, familial and social implications of the genetic contribution to disease. Genetic counseling is particularly helpful for couples with recurrent miscarriages, advanced maternal age, a partner with a chromosome translocation or inversion, those in a consanguineous marriage, and those using donor gametes. Partners with a family history of genetic conditions including hereditary cancer, late onset neurological diseases and with a carrier status for monogenic disorders can benefit from genetic counseling when undergoing PGT for monogenic disorders (PGT-M). Genetic counseling for PGT is useful in cases of Mendelian disorders, autosomal dominant and recessive conditions and sex chromosome linked disorders and for the purposes of utilizing HLA matching technology for creating a savior sibling. It also helps in understanding the importance of PGT in cases of variants of uncertain significance (VUS) and variable penetrance. The possibilities and limitations are discussed in detail during the sessions of genetic counseling.

Lafora Disease: A Case Report and Evolving Treatment Advancements

Lafora disease is a rare genetic disorder characterized by a disruption in glycogen metabolism. It manifests as progressive myoclonus epilepsy and cognitive decline during adolescence. Pathognomonic is the presence of abnormal glycogen aggregates that, over time, produce large inclusions (Lafora bodies) in various tissues. This study aims to describe the clinical and histopathological aspects of a novel Lafora disease patient, and to provide an update on the therapeutical advancements for this disorder. A 20-year-old Libyan boy presented with generalized tonic-clonic seizures, sporadic muscular jerks, eyelid spasms, and mental impairment. Electroencephalography showed multiple discharges across both brain hemispheres. Brain magnetic resonance imaging was unremarkable. Muscle biopsy showed increased lipid content and a very mild increase of intermyofibrillar glycogen, without the polyglucosan accumulation typically observed in Lafora bodies. Despite undergoing three lines of antiepileptic treatment, the patient's condition showed minimal to no improvement. We identified the homozygous variant c.137G>A, p.(Cys46Tyr), in the EPM2B/NHLRC1 gene, confirming the diagnosis of Lafora disease. To our knowledge, the presence of lipid aggregates without Lafora bodies is atypical. Lafora disease should be considered during the differential diagnosis of progressive, myoclonic, and refractory epilepsies in both children and young adults, especially when accompanied by cognitive decline. Although there are no effective therapies yet, the development of promising new strategies prompts the need for an early and accurate diagnosis.

The c.1243T>C mutation in the PROC gene is linked with inherited protein C deficiency and severe purpura fulminans

Purpura fulminans is a severe coagulation disorder that often leads to death in neonates. Mutations in the protein C (PROC) gene can cause protein C deficiency, leading to this disorder. This study aimed to investigate a family with a history of coagulopathies, particularly those related to protein C deficiency. The primary objective was to identify any genetic mutations in the PROC gene responsible for the coagulopathies. The study focused on a male neonate with purpura fulminans who ultimately died at 2 months of age. The patient had low protein C activity levels (6%). The entire PROC gene of the patient and his family was analyzed using next-generation sequencing to identify any genetic mutations. Segregation analysis was conducted to determine if the mutation followed an autosomal dominant inheritance pattern. In silico analysis was also conducted to evaluate the pathogenicity of the identified mutation. Analysis revealed a novel homozygous c.1243T>G variant PROC gene. The mutation resulted in a Phe415Val substitution. The mutation was found in at least three generations of the family. Carrier family members had lower protein C activity levels than wild-type homozygotes. Additionally, the mutation may account for the observed reduction in protein C enzyme activity.

Comprehensive review on the pathogenesis of hypertriglyceridaemia-associated acute pancreatitis

It is well known, that the inflammatory process that characterizes acute pancreatitis (AP) can lead to both pancreatic damage and systemic inflammatory response syndrome (SIRS). During the last 20 years, there has been a growing incidence of episodes of acute pancreatitis associated with hypertriglyceridaemia (HTAP). This review provides an overview of triglyceride metabolism and the potential mechanisms that may contribute to developing or exacerbating HTAP. The article comprehensively discusses the various pathological roles of free fatty acid, inflammatory response mechanisms, the involvement of microcirculation, serum calcium overload, oxidative stress and the endoplasmic reticulum, genetic polymorphism, and gut microbiota, which are known to trigger or escalate this condition. Future perspectives on HTAP appear promising, with ongoing research focused on developing more specific and effective treatment strategies.

Severe complications in the induction phase of therapy in a pediatric patient with T-cell acute lymphoblastic leukemia: A case report

RATIONALE

Acute lymphoblastic leukemia (ALL) represents approximately 1-quarter of all new cases of childhood cancer. Although overall survival following diagnosis has improved in recent years, the toxicity of chemotherapy remains a concern.

PATIENT CONCERNS

We describe an 11-year-old male patient diagnosed with T-cell precursor ALL who developed compounded complications during the induction phase of chemotherapy. Patient was hospitalized in the Department of Pediatric Hematology, Oncology, and Transplantology of the Medical University of Lublin, Poland. The patient's induction therapy was started according to the AIEOP-BFM ALL 2017 protocol IAp (International Collaborative Treatment Protocol for Children and Adolescents with Acute Lymphoblastic Leukemia).

DIAGNOSES

Patient developed compounded complications such as cholecystitis, hepatotoxicity, pancreatitis and myelosuppression.

INTERVENTIONS

The patient was treated with leukapheresis, received a broad-spectrum antibiotic, potassium supplementation and hepatoprotective treatment and laparotomy cholecystectomy.

OUTCOMES

In the available literature, there is a limited amount of similar clinical cases with multiple complications in pediatric patients with ALL. Toxicities cause delays in the treatment of the underlying disease.

LESSONS

In children with acute lymphoblastic leukemia, there are side effects during the treatment such as cholecystitis and pancreatitis. Complications during treatment require a quick response and modification of disease management. Abdominal ultrasound performed before treatment makes it possible to observe the dynamics of lesions. Genetic mutation analysis could allow us to more precisely respond to the possible susceptibility to and appearance of complications after the use of a given chemotherapeutic agent.

Identification of protease-sensitive but not misfolding PNLIP variants in familial and hereditary pancreatitis

Mutations in the PNLIP gene have recently been implicated in chronic pancreatitis. Several PNLIP missense variants have been reported to cause protein misfolding and endoplasmic reticulum stress although genetic evidence supporting their association with chronic pancreatitis is currently lacking. Protease-sensitive PNLIP missense variants have also been associated with early-onset chronic pancreatitis although the underlying pathological mechanism remains enigmatic. Herein, we provide new evidence to support the association of protease-sensitive PNLIP variants (but not misfolding PNLIP variants) with pancreatitis. Specifically, we identified protease-sensitive PNLIP variants in 5 of 373 probands (1.3%) with a positive family history of pancreatitis. The protease-sensitive variants, p.F300L and p.I265R, were found to segregate with the disease in three families, including one exhibiting a classical autosomal dominant inheritance pattern. Consistent with previous findings, protease-sensitive variant-positive patients were often characterized by early-onset disease and invariably experienced recurrent acute pancreatitis, although none has so far developed chronic pancreatitis.

Classification of PRSS1 variants responsible for chronic pancreatitis: An expert perspective from the Franco-Chinese GREPAN study group

BACKGROUND

PRSS1 was the first reported chronic pancreatitis (CP) gene. The existence of both gain-of-function (GoF) and gain-of-proteotoxicity (GoP) pathological PRSS1 variants, together with the fact that PRSS1 variants have been identified in CP subtypes spanning the range from monogenic to multifactorial, has made the classification of PRSS1 variants very challenging.

METHODS

All currently reported PRSS1 variants (derived primarily from two databases) were manually reviewed with respect to their clinical genetics, functional analysis and population allele frequency. They were classified by variant type and pathological mechanism within the framework of our recently proposed ACMG/AMP guidelines-based seven-category system.

RESULTS

The total number of distinct germline PRSS1 variants included for analysis was 100, comprising 3 copy number variants (CNVs), 12 5' and 3' variants, 19 intronic variants, 5 nonsense variants, 1 frameshift deletion variant, 6 synonymous variants, 1 in-frame duplication, 3 gene conversions and 50 missense variants. Based upon a combination of clinical genetic and functional analysis, population data and in silico analysis, we classified 26 variants (all 3 CNVs, the in-frame duplication, all 3 gene conversions and 19 missense) as "pathogenic", 3 variants (missense) as "likely pathogenic", 5 variants (four missense and one promoter) as "predisposing", 13 variants (all missense) as "unknown significance", 2 variants (missense) as "likely benign", and all remaining 51 variants as "benign".

CONCLUSIONS

We describe an expert classification of the 100 PRSS1 variants reported to date. The results have immediate implications for reclassifying many ClinVar-registered PRSS1 variants as well as providing optimal guidelines/standards for reporting PRSS1 variants.

Reducing Premature Coronary Artery Disease in Malaysia by Early Identification of Familial Hypercholesterolemia Using the Familial Hypercholesterolemia Case Ascertainment Tool (FAMCAT): Protocol for a Mixed Methods Evaluation Study

BACKGROUND

Familial hypercholesterolemia (FH) is predominantly caused by mutations in the 4 FH candidate genes (FHCGs), namely, low-density lipoprotein receptor (LDLR), apolipoprotein B-100 (APOB-100), proprotein convertase subtilisin/kexin type 9 (PCSK9), and the LDL receptor adaptor protein 1 (LDLRAP1). It is characterized by elevated low-density lipoprotein cholesterol (LDL-c) levels leading to premature coronary artery disease. FH can be clinically diagnosed using established clinical criteria, namely, Simon Broome (SB) and Dutch Lipid Clinic Criteria (DLCC), and can be identified using the Familial Hypercholesterolemia Case Ascertainment Tool (FAMCAT), a primary care screening tool.

OBJECTIVE

This study aims to (1) compare the detection rate of genetically confirmed FH and diagnostic accuracy between the FAMCAT, SB, and DLCC in the Malaysian primary care setting; (2) identify the genetic mutation profiles, including novel variants, in individuals with suspected FH in primary care; (3) explore the experience, concern, and expectation of individuals with suspected FH who have undergone genetic testing in primary care; and (4) evaluate the clinical utility of a web-based FH Identification Tool that includes the FAMCAT, SB, and DLCC in the Malaysian primary care setting.

METHODS

This is a mixed methods evaluation study conducted in 11 Ministry of Health primary care clinics located at the central administrative region of Malaysia. In Work stream 1, the diagnostic accuracy study design is used to compare the detection rate and diagnostic accuracy of the FAMCAT, SB, and DLCC against molecular diagnosis as the gold standard. In Work stream 2, the targeted next-generation sequencing of the 4 FHCGs is used to identify the genetic mutation profiles among individuals with suspected FH. In Work stream 3a, a qualitative semistructured interview methodology is used to explore the experience, concern, and expectation of individuals with suspected FH who have undergone genetic testing. Lastly, in Work stream 3b, a qualitative real-time observation of primary care physicians using the "think-aloud" methodology is applied to evaluate the clinical utility of a web-based FH Identification Tool.

RESULTS

The recruitment for Work stream 1, and blood sampling and genetic analysis for Work stream 2 were completed in February 2023. Data collection for Work stream 3 was completed in March 2023. Data analysis for Work streams 1, 2, 3a, and 3b is projected to be completed by June 2023, with the results of this study anticipated to be published by December 2023.

CONCLUSIONS

This study will provide evidence on which clinical diagnostic criterion is the best to detect FH in the Malaysian primary care setting. The full spectrum of genetic mutations in the FHCGs including novel pathogenic variants will be identified. Patients' perspectives while undergoing genetic testing and the primary care physicians experience in utilizing the web-based tool will be established. These findings will have tremendous impact on the management of patients with FH in primary care and subsequently reduce their risk of premature coronary artery disease.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/47911.

Specifications and validation of the ACMG/AMP criteria for clinical interpretation of sequence variants in collagen genes associated with joint hypermobility

Deleterious variants in collagen genes are the most common cause of hereditary connective tissue disorders (HCTD). Adaptations of the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) criteria are still lacking. A multidisciplinary team was set up for developing specifications of the ACMG/AMP criteria for COL1A1, COL1A2, COL2A1, COL3A1, COL5A1, COL5A2, COL11A1, COL11A2 and COL12A1, associated with various forms of HCTD featuring joint hypermobility, which is becoming one of the most common reasons of referral for molecular testing in this field. Such specifications were validated against 209 variants, and resulted effective for classifying as pathogenic and likely pathogenic null alleles without downgrading of the PVS1 level of strength and recurrent Glycine substitutions. Adaptations of selected criteria reduced uncertainties on private Glycine substitutions, intronic variants predicted to affect the splicing, and null alleles with a downgraded PVS1 level of strength. Segregation and multigene panel sequencing data mitigated uncertainties on non-Glycine substitutions by the attribution of one or more benignity criteria. These specifications may improve the clinical utility of molecular testing in HCTD by reducing the number of variants with neutral/conflicting interpretations. Close interactions between laboratory and clinicians are crucial to estimate the a priori utility of molecular test and to improve medical reports.

Genetic determinants of pancreatitis: relevance in severe hypertriglyceridemia

PURPOSE OF REVIEW

Not all patients with severe hypertriglyceridemia develop acute pancreatitis. We surveyed recent literature on inter-individual genetic variation in susceptibility to pancreatitis.

RECENT FINDINGS

Genetic determinants of pancreatitis include: rare Mendelian disorders caused by highly penetrant pathogenic variants in genes involved in trypsinogen activation; uncommon susceptibility variants in genes involved in trypsinogen activation, protein misfolding as well as calcium metabolism and cystic fibrosis, that have variable penetrance and show a range of odds ratios for pancreatitis; and common polymorphisms in many of the same genes that have only a small effect on risk. The role of these genetic variants in modulating pancreatitis risk in hypertriglyceridemia is unclear. However, among genetic determinants of plasma triglycerides, those predisposing to more severe hypertriglyceridemia associated with chylomicronemia appear to have higher pancreatitis risk.

SUMMARY

Currently, among patients with severe hypertriglyceridemia, the most consistent predictor of pancreatitis risk is the triglyceride level. Furthermore, pancreatitis risk appears to be modulated by a higher genetic burden of factors associated with greater magnitude of triglyceride elevation. The role of common and rare genetic determinants of pancreatitis itself in this metabolic context is unclear.

The PRSS3P2 and TRY7 deletion copy number variant modifies risk for chronic pancreatitis

BACKGROUND

PRSS1 and PRSS2 constitute the only functional copies of a tandemly-arranged five-trypsinogen-gene cluster (i.e., PRSS1, PRSS3P1, PRSS3P2, TRY7 and PRSS2) on chromosome 7q35. Variants in PRSS1 and PRSS2, including missense and copy number variants (CNVs), have been reported to predispose to or protect against chronic pancreatitis (CP). We wondered whether a common trypsinogen pseudogene deletion CNV (that removes two of the three trypsinogen pseudogenes, PRSS3P2 and TRY7) might be associated with CP causation/predisposition.

METHODS

We analyzed the common PRSS3P2 and TRY7 deletion CNV in a total of 1536 CP patients and 3506 controls from France, Germany, India and Japan by means of quantitative fluorescent multiplex polymerase chain reaction.

RESULTS

We demonstrated that the deletion CNV variant was associated with a protective effect against CP in the French, German and Japanese cohorts whilst a trend toward the same association was noted in the Indian cohort. Meta-analysis under a dominant model yielded a pooled odds ratio (OR) of 0.68 (95% confidence interval (CI) 0.52-0.89; p = 0.005) whereas an allele-based meta-analysis yielded a pooled OR of 0.84 (95% CI 0.77-0.92; p = 0.0001). This protective effect is explicable by reference to the recent finding that the still functional PRSS3P2/TRY7 pseudogene enhancers upregulate pancreatic PRSS2 expression.

CONCLUSIONS

The common PRSS3P2 and TRY7 deletion CNV was associated with a reduced risk for CP. This finding provides additional support for the emerging view that dysregulated PRSS2 expression represents a discrete mechanism underlying CP predisposition or protection.

Case report: A novel mutation in RTEL1 gene in dyskeratosis congenita

Dyskeratosis congenita (DKC), also known as Zinsser-Cole-Engman syndrome, is a telomeropathy typically presenting as a triad of leukoplakia, nail dystrophy, and reticular hyperpigmentation. Reported genetic mutations linked to DKC include DKC1, TINF2, TERC, TERT, C16orf57, NOLA2, NOLA3, WRAP53/TCAB1, and RTEL1. Homozygous, compound heterozygous, and heterozygous mutations in RTEL1 (RTEL1, regulator of telomere elongation helicase 1) gene on chromosome 20q13 are known to cause autosomal dominant as well as recessive DKC. Pathogenic variants of RTEL1 gene in DKC patients include c.2288G>T (p. Gly763Val), c.3791G>A (p. Arg1264His), and RTEL p. Arg981Trp. We report a novel homozygous variant of RTEL1, transcript ID: ENST00000360203.11, exon 24, c.2060C>T (p.Ala687Val), in a patient of DKC presenting with leukoplakia, dystrophic nails, reticulate pigmentation, and positive family history of a similar phenotype. The novel variant, reported as a variant of uncertain significance, may therefore be considered diagnostic for DKC in a Pakistani population.