Hereditary cancer syndromes are among the most common inherited disorders and contribute to nearly 10% of solid tumours. While genetic testing is now central to diagnosis, surveillance, and cascade prevention, its impact is constrained by the persistent challenge of variants of uncertain significance (VUS), which comprise almost 40% of reported hereditary cancer syndrome-associated variants in ClinVar. These unresolved classifications undermine the interpretive power of testing, limiting its translational and preventive potential. In this review, we examine the foundations of variant interpretation, the role of expert-guided specifications, and emerging methods for VUS reclassification, including population-level data, RNA- and protein-based functional assays, computational predictors, and long-read sequencing. We further highlight how systematic re-evaluation structures and curation infrastructures translate new evidence into clinical practice. We conclude with an outlook on future directions to reduce the burden of VUS and increase the clinical utility of hereditary cancer syndrome testing.

Background & Aims Individuals with colorectal polyposis are suspected to be genetically predisposed to tumor development. However, in around half of adenomatous and the vast majority of serrated polyposis patients, no explanatory pathogenic germline variant is found in routine diagnostics. Here, we aimed to improve the characterization of the early steps of polyp formation and provide clues on the tumorigenic processes involved. Methods We performed whole-exome sequencing of colorectal tumors (n = 299) from 153 individuals with adenomatous or serrated polyposis and 16 individuals with early-onset colorectal cancer in the absence of known pathogenic germline variants. Subsequently, somatic mutations were called and a driver gene analysis for pathogenicity was performed. In addition, CpG island methylator phenotypes, tumor mutational burden, microsatellite instability, and mutational signatures were analyzed and compared with publicly available datasets of molecularly profiled colorectal cancers and polyps. Results Somatic mutations in APC/CTNNB1 and BRAF were significantly more frequent in adenomatous and serrated polyps, respectively. APC mosaicism was identified in 19% of individuals with adenomatous polyposis. In 9% of serrated polyps, a CpG island methylator phenotypes high methylation status was detected. Almost all polyps presented with a low tumor mutational burden and the majority were microsatellite stable. In APC/CTNNB1- and BRAF-mutated polyps, we identified a significantly lower contribution of the clock-like signature SBS1 and a significantly higher contribution of the normal colon tissue signature SBS89, respectively, compared with sporadic colorectal tumors. Conclusions Our results indicate that BRAF-mutated serrated polyps are molecularly more similar to normal colon tissue than APC- and/or CTNNB1-mutated tumors. Overall, molecular tumor profiling of individuals with polyposis contributes to understanding the genetic disease etiology.

Mutations in CHRNE encoding the epsilon subunit of acetylcholine receptor result in impaired neuromuscular transmission and congenital myasthenic syndrome (CMS) with variying severity of symptoms. Although the pathophysiology is well-known, blood biomarker signatures enabling a patient-stratification are lacking. This retrospective two-center-study includes 19 recessive CHRNE-patients (AChR deficiency; mean age 14.8 years) from 13 families which were clinically characterized according to disease severity. 15 patients were classified as mildly and 4 patients as moderate to severely affected. Seven known pathogenic and one unreported variant (c.1032 + 2_1032 + 3delinsGT) were identified. Biomarker discovery was carried out on blood samples: proteomics was performed on white blood cells (WBC; n = 12) and on extracellular vesicles (EV) purified from serum samples (n = 7) in addition to amino acid profiling (n = 9) and miRNA screening (n = 18). For miRNA studies, 7 patients with other CMS-subtypes were moreover included. WBC-proteomics unveiled a significant increase of 7 and a decrease of 36 proteins. In silico studies of these proteins indicated affection of secretory granules and the extracellular space. Comparison across patients unveiled increase of two vesicular transport proteins (SCAMP2 and SNX2) in severely affected patients and indeed EV-proteomics revealed increase of 7 and decrease of 13 proteins. Three of these proteins (TARSH, ATRN PLEC) are known to be important for synaptogenesis and synaptic function. Metabolomics showed decrease of seven amino acids/ amino acid metabolites (aspartic and glutamic acids, phosphoserine, amino adipate, citrulline, ornithine, and 1-methyhistidine). miRNA-profiling showed increase miR − 483 − 3p, miR-365a-3p, miR − 365b − 3p and miR-99a, and decrease of miR-4433b-3p, miR-6873-3p, miR-182-5p and let-7b-5p in CHRNE-patients whereas a comparison with other CMS subtypes showed increase of miR − 205 − 5p, miR − 10b − 5p, miR-125a-5p, miR-499-5p, miR-3120-5p and miR − 483 − 5p and decrease of miR − 1290. Our combined data introduce a molecular fingerprint on protein, metabolic and miRNA level with some of those playing different roles along the neuromuscular axis.

Genetic tumor risk syndromes (genturis) contribute substantially to the overall cancer burden and provide opportunities for early detection, prevention, and individualized treatment. Yet, many affected individuals remain undiagnosed due to restrictive testing criteria and challenges in variant interpretation. This review summarizes recent advances in the diagnostic evaluation of genturis. We trace the evolution from single‐gene testing to multigene panel testing, highlighting gains in diagnostic yield alongside the growing prevalence of uncertain and incidental findings. We then describe emerging functional approaches such as RNA sequencing and proteomics that generate molecular evidence to refine variant classification. Next, we outline how long‐read sequencing overcomes technical limitations in complex genomic regions. Finally, we discuss practical aspects of clinical implementation, including reporting practices, workflow integration, and professional education, and propose strategies to improve diagnostic accuracy, efficiency, and equitable access to testing.

Interpreting variants of uncertain significance (VUS) in mismatch repair (MMR) genes remains a major challenge in managing Lynch syndrome and other hereditary cancer syndromes. This review outlines recommended VUS classification procedures, encompassing foundational and specialized methodologies tailored for MMR genes by expert organizations, including InSiGHT and ClinGen’s Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel (VCEP). Key approaches include: (1) functional data, encompassing direct assays measuring MMR proficiency such as in vitro MMR assays, deep mutational scanning, and MMR cell-based assays, as well as techniques like methylation-tolerant assays, proteomic-based approaches, and RNA sequencing, all of which provide critical functional evidence supporting variant pathogenicity; (2) computational data/tools, including in silico meta-predictors and models, which contribute to robust VUS classification when integrated with experimental evidence; and (3) enhanced variant detection to identify the actual causal variant through whole-genome sequencing and long-read sequencing to detect pathogenic variants missed by traditional methods. These strategies improve diagnostic precision, support clinical decision-making for Lynch syndrome, and establish a flexible framework that can be applied to other OMIM-listed genes.

As multigene panel testing is becoming routine in clinical care, there are recommendations at national and international level, as to which genes should be analyzed in the context of a hereditary breast and ovarian cancer (HBOC). However, the individual composition of gene panels offered by testing laboratories vary, resulting in a different variant diagnostic rate. Therefore, we performed a retrospective NGS dataset analysis of suspected HBOC patients who had been tested at different German diagnostic laboratories that are part of the NASGE network. We collected 29,317 HBOC datasets and compared the diagnostic yield applying the most common panel recommendations and an internal HBOC gene panel. Additionally, we analyzed the data concerning other potential tumor risk syndromes (TRS) not caused by pathogenic variants in the core panel genes. At least one pathogenic variant causative for an autosomal-dominant TRS was identified in 4235 datasets, resulting in an overall diagnostic yield of 14.4 %. The diagnostic yield of pathogenic variants varied depending on the applied HBOC panel (between 5 and 26 genes) from 9.0 % to 13.8 % with the internal HBOC panel having a yield of 12.7 %. Notably, in about 1 % of cases, a pathogenic variant outside the established HBOC core genes was identified, indicating the presence of other TRS. These results are consistent with previous observations that a significant proportion of patients with HBOC predisposition were not detected by the guideline-based gene panels and suggest that expanded diagnostics compared to currently recommended multigene panels may identify additional patients at high risk for developing cancer.

BACKGROUND:The classification of sequence variants is at the core of human genetic diagnostics and is the basis for clinical guidance - incorrectly classified variants may cause great harm to patients and their families. METHODS:We provide an overview of the evolution of ideas and algorithms that have led to the formulation of elaborate classification systems over the last decades, culminating in the ACMG/AMP classification system. Furthermore, we address a still unsolved problem in the clinical translation of DNA analyses: variants of unclear significance (VUS). RESULTS:Rigorous data sharing and the sub-categorisation of VUS could facilitate a clearer interpretation of VUS. CONCLUSION:This review underscores the efforts of the HUGO Education Committee to empower professional-sespecially in resource-limited settings-with the expertise needed for high-quality variant interpretation, fostering equitable access to the transformative potential of genomic medicine.

Congenital eye malformations like microphthalmia-anophthalmia-coloboma (MAC), anterior segment dysgenesis (ASD), primary congenital glaucoma (PCG) and congenital cataracts (CC) are significant causes of childhood visual impairment. Phenotypic heterogeneity often complicates diagnosis. The goal of this study was to optimize the diagnostic strategy for next-generation sequencing (NGS)-based procedures, thereby aiming to identify genetic causes of congenital eye malformations. Forty patients with congenital eye malformations were included. A primary diagnostic testing (PD) of a limited number of genes was followed by multigene panel (MGP) testing, including 186 eye-related genes, and exome sequencing. Causative variants were identified in 17 patients (43%) and clinically relevant variants of uncertain significance (VUS) in 6 patients (15%). PD had a diagnostic yield (DY) of 15%, MGP of 29% and exome sequencing of 4%, leading to a cumulative DY of 43%. Diagnostic rates were highest in CC (75%), bilateral cases (46%), complex ocular phenotypes (78%), patients with extraocular manifestations (55%) and positive family history (70%). Rare and possible new genotype-phenotype correlations and candidate genes (FAT1, POGZ) could be identified. In total, eight (likely) pathogenic variants in six genes (CYP1B1, ADAMTS18, MAB21L2, NHS, MFRP, CRYBB1) were not yet reported. A stepwise genetic testing approach starting with a broad multigene panel followed by exome sequencing provides higher diagnostic yield than limited phenotype-specific testing. Comprehensive genetic diagnosis is essential for prognosis, treatment and genetic counseling, underscoring the need for routine genetic testing and interdisciplinary collaboration in managing congenital eye malformations.

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.

Pathogenic constitutional APC variants underlie familial adenomatous polyposis, the most common hereditary gastrointestinal polyposis syndrome. To improve variant classification and resolve the interpretative challenges of variants of uncertain significance (VUSs), APC-specific variant classification criteria were developed by the ClinGen-InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel (VCEP) based on the criteria of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP). A streamlined algorithm using the APC-specific criteria was developed and applied to assess all APC variants in ClinVar and the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) international reference APC Leiden Open Variation Database (LOVD) variant database, which included a total of 10,228 unique APC variants. Among the ClinVar and LOVD variants with an initial classification of (likely) benign or (likely) pathogenic, 94% and 96% remained in their original categories, respectively. In contrast, 41% ClinVar and 61% LOVD VUSs were reclassified into clinically meaningful classes, the vast majority as (likely) benign. The total number of VUSs was reduced by 37%. In 24 out of 37 (65%) promising APC variants that remained VUS despite evidence for pathogenicity, a data-mining-driven work-up allowed their reclassification as (likely) pathogenic. These results demonstrated that the application of APC-specific criteria substantially reduced the number of VUSs in ClinVar and LOVD. The study also demonstrated the feasibility of a systematic approach to variant classification in large datasets, which might serve as a generalizable model for other gene- or disease-specific variant interpretation initiatives. It also allowed for the prioritization of VUSs that will benefit from in-depth evidence collection. This subset of APC variants was approved by the VCEP and made publicly available through ClinVar and LOVD for widespread clinical use.

Fatty acid hydroxylase-associated neurodegeneration (FAHN/SPG35) is caused by pathogenic variants in FA2H and has been linked to a continuum of specific motor and non-motor neurological symptoms, leading to progressive disability. As an ultra-rare disease, its mutational spectrum has not been fully elucidated. Here, we present the prototypical workup of a novel FA2H variant, including clinical and in silico validation. An 18-year-old male patient presented with a history of childhood-onset progressive cognitive impairment, as well as progressive gait disturbance and lower extremity muscle cramps from the age of 15. Additional symptoms included exotropia, dystonia, and limb ataxia. Trio exome sequencing revealed a novel homozygous c.75C>G (p.Cys25Trp) missense variant in the FA2H gene, which was located in the cytochrome b5 heme-binding domain. Evolutionary conservation, prediction models, and structural protein modeling indicated a pathogenic loss of function. Brain imaging showed characteristic features, thus fulfilling the complete multisystem neurodegenerative phenotype of FAHN/SPG35. In summary, we here present a novel FA2H variant and provide prototypical clinical findings and structural analyses underpinning its pathogenicity.

Background:Pathogenic constitutional APC variants underlie familial adenomatous polyposis, the most common hereditary gastrointestinal polyposis syndrome. To improve variant classification and resolve the interpretative challenges of variants of uncertain significance (VUS), APC-specific ACMG/AMP variant classification criteria were developed by the ClinGen-InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel (VCEP). Methods:A streamlined algorithm using the APC -specific criteria was developed and applied to assess all APC variants in ClinVar and the InSiGHT international reference APC LOVD variant database. Results:A total of 10,228 unique APC variants were analysed. Among the ClinVar and LOVD variants with an initial classification of (Likely) Benign or (Likely) Pathogenic, 94% and 96% remained in their original categories, respectively. In contrast, 41% ClinVar and 61% LOVD VUS were reclassified into clinically actionable classes, the vast majority as (Likely) Benign. The total number of VUS was reduced by 37%. In 21 out of 36 (58%) promising APC variants that remained VUS despite evidence for pathogenicity, a data mining-driven work-up allowed their reclassification as (Likely) Pathogenic. Conclusions:The application of APC -specific criteria substantially reduced the number of VUS in ClinVar and LOVD. The study also demonstrated the feasibility of a systematic approach to variant classification in large datasets, which might serve as a generalisable model for other gene-/disease-specific variant interpretation initiatives. It also allowed for the prioritization of VUS that will benefit from in-depth evidence collection. This subset of APC variants was approved by the VCEP and made publicly available through ClinVar and LOVD for widespread clinical use.

Background: NEFL encodes for the neurofilament light chain protein. Pathogenic variants in NEFL cause demyelinating, axonal and intermediate forms of Charcot-Marie-Tooth disease (CMT) which present with a varying degree of severity and somatic mutations have not been described yet. Currently, 34 different CMT-causing pathogenic variants in NEFL in 174 patients have been reported. Muscular involvement was also described in CMT2E patients mostly as a secondary effect. Also, there are a few descriptions of a primary muscle vulnerability upon pathogenic NEFL variants. Objectives: To expand the current knowledge on the genetic landscape, clinical presentation and muscle involvement in NEFL-related neurological diseases by retrospective case study and literature review. Methods: We applied in-depth phenotyping of new and already reported cases, molecular genetic testing, light-, electron- and Coherent Anti-Stokes Raman Scattering-microscopic studies and proteomic profiling in addition to in silico modelling of NEFL-variants. Results: We report on a boy with a muscular phenotype (weakness, myalgia and cramps, Z-band alterations and mini-cores in some myofibers) associated with the heterozygous p.(Phe104Val) NEFL -variant, which was previously described in a neuropathy case. Skeletal muscle proteomics findings indicated affection of cytoskeletal proteins. Moreover, we report on two further neuropathic patients (16 years old girl and her father) both carrying the heterozygous p.(Pro8Ser) variant, which has been identified as 15% somatic mosaic in the father. While the daughter presented with altered neurophysiology,neurogenic clump feet and gait disturbances, the father showed clinically only feet deformities. As missense variants affecting proline at amino acid position 8 are leading to neuropathic manifestations of different severities, in silico modelling of these different amino acid substitutions indicated variable pathogenic impact correlating with disease onset. Conclusions: Our findings provide new morphological and biochemical insights into the vulnerability of denervated muscle (upon NEFL-associated neuropathy) as well as novel genetic findings expanding the current knowledge on NEFL-related neuromuscular phenotypes and their clinical manifestations. Along this line, our data show that even subtle expression of somatic NEFL variants can lead to neuromuscular symptoms. Keywords Neurofilament light chain , protein accumulation , muscle proteomics , somatic mutation , CARS microscopy muscle

BACKGROUND:Based on a limited number of reported families, biallelic CA8 variants have currently been associated with a recessive neurological disorder named, cerebellar ataxia, mental retardation, and dysequilibrium syndrome 3 (CAMRQ-3). OBJECTIVES:We aim to comprehensively investigate CA8-related disorders (CA8-RD) by reviewing existing literature and exploring neurological, neuroradiological, and molecular observations in a cohort of newly identified patients. METHODS:We analyzed the phenotype of 27 affected individuals from 14 families with biallelic CA8 variants (including data from 15 newly identified patients from eight families), ages 4 to 35 years. Clinical, genetic, and radiological assessments were performed, and zebrafish models with ca8 knockout were used for functional analysis. RESULTS:Patients exhibited varying degrees of neurodevelopmental disorders (NDD), along with predominantly progressive cerebellar ataxia and pyramidal signs and variable bradykinesia, dystonia, and sensory impairment. Quadrupedal gait was present in only 10 of 27 patients. Progressive selective cerebellar atrophy, predominantly affecting the superior vermis, was a key diagnostic finding in all patients. Seven novel homozygous CA8 variants were identified. Zebrafish models demonstrated impaired early neurodevelopment and motor behavior on ca8 knockout. CONCLUSION:Our comprehensive analysis of phenotypic features indicates that CA8-RD exhibits a wide range of clinical manifestations, setting it apart from other subtypes within the category of CAMRQ. CA8-RD is characterized by cerebellar atrophy and should be recognized as part of the autosomal-recessive cerebellar ataxias associated with NDD. Notably, the presence of progressive superior vermis atrophy serves as a valuable diagnostic indicator. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.