Functional and clinical studies reveal pathophysiological complexity of CLCN4-related neurodevelopmental condition.

Missense and truncating variants in the X-chromosome-linked CLCN4 gene, resulting in reduced or complete loss-of-function (LOF) of the encoded chloride/proton exchanger ClC-4, were recently demonstrated to cause a neurocognitive phenotype in both males and females. Through international clinical matchmaking and interrogation of public variant databases we assembled a database of 90 rare CLCN4 missense variants in 90 families: 41 unique and 18 recurrent variants in 49 families. For 43 families, including 22 males and 33 females, we collated detailed clinical and segregation data. To confirm causality of variants and to obtain insight into disease mechanisms, we investigated the effect on electrophysiological properties of 59 of the variants in Xenopus oocytes using extended voltage and pH ranges. Detailed analyses revealed new pathophysiological mechanisms: 25% (15/59) of variants demonstrated LOF, characterized by a "shift" of the voltage-dependent activation to more positive voltages, and nine variants resulted in a toxic gain-of-function, associated with a disrupted gate allowing inward transport at negative voltages. Functional results were not always in line with in silico pathogenicity scores, highlighting the complexity of pathogenicity assessment for accurate genetic counselling. The complex neurocognitive and psychiatric manifestations of this condition, and hitherto under-recognized impacts on growth, gastrointestinal function, and motor control are discussed. Including published cases, we summarize features in 122 individuals from 67 families with CLCN4-related neurodevelopmental condition and suggest future research directions with the aim of improving the integrated care for individuals with this diagnosis.

Comparative analysis of gene and disease selection in genomic newborn screening studies.

Genomic newborn screening (gNBS) is on the horizon given the decreasing costs of sequencing and the advanced understanding of the impact of genetic variants on health and diseases. Key to ongoing gNBS pilot studies is the selection of target diseases and associated genes to be included. In this study, we present a comprehensive analysis of seven published gene-disease lists from gNBS studies, evaluating gene-disease count, composition, group proportions, and ClinGen curations of individual disorders. Despite shared selection criteria, we observe substantial variation in total gene count (median 480, range 237-889) and disease group composition. An intersection was identified for 53 genes, primarily inherited metabolic diseases (83%, 44/53). Each study investigated a subset of exclusive gene-disease pairs, and the total number of exclusive gene-disease pairs was positively correlated with the total number of genes included per study. While most pairs receive "Definitive" or "Strong" ClinGen classifications, some are labeled as "Refuted" (n = 5) or "Disputed" (n = 28), particularly in genetic cardiac diseases. Importantly, 17%-48% of genes lack ClinGen curation. This study underscores the current absence of consensus recommendations for selection criteria for target diseases for gNBS resulting in diversity in proposed gene-disease pairs, their coupling with gene variations and the use of ClinGen curation. Our findings provide crucial insights into the selection of target diseases and accompanying gene variations for future gNBS program, emphasizing the necessity for ongoing collaboration and discussion about criteria harmonization for panel selection to ensure the screening's objectivity, integrity, and broad acceptance.

Bi-allelic loss-of-function variants in KIF21A cause severe fetal akinesia with arthrogryposis multiplex.

BACKGROUND: Fetal akinesia (FA) results in variable clinical presentations and has been associated with more than 166 different disease loci. However, the underlying molecular cause remains unclear in many individuals. We aimed to further define the set of genes involved. METHODS: We performed in-depth clinical characterisation and exome sequencing on a cohort of 23 FA index cases sharing arthrogryposis as a common feature. RESULTS: We identified likely pathogenic or pathogenic variants in 12 different established disease genes explaining the disease phenotype in 13 index cases and report 12 novel variants. In the unsolved families, a search for recessive-type variants affecting the same gene was performed; and in five affected fetuses of two unrelated families, a homozygous loss-of-function variant in the kinesin family member 21A gene (KIF21A) was found. CONCLUSION: Our study underlines the broad locus heterogeneity of FA with well-established and atypical genotype-phenotype associations. We describe KIF21A as a new factor implicated in the pathogenesis of severe neurogenic FA sequence with arthrogryposis of multiple joints, pulmonary hypoplasia and facial dysmorphisms. This hypothesis is further corroborated by a recent report on overlapping phenotypes observed in Kif21a null piglets.

Assigning evidence to actionability: An introduction to variant interpretation in precision cancer medicine.

Modern concepts in precision cancer medicine are based on increasingly complex genomic analyses and require standardized criteria for the functional evaluation and reporting of detected genomic alterations in order to assess their clinical relevance. In this article, we propose and address the necessary steps in systematic variant evaluation consisting of bioinformatic analysis, functional annotation and clinical interpretation, focusing on the latter two aspects. We discuss the role and clinical application of current variant classification systems and point out their scope and limitations. Finally, we highlight the significance of the molecular tumor board as a platform for clinical decision-making based on genomic analyses.

Germline testing for homologous recombination repair genes-opportunities and challenges.

Pathogenic variants in the BRCA1 and BRCA2 genes are well known causes of hereditary breast and ovarian cancer. Other genes involved in the homologous recombination pathway can also be associated with increased probability of cancer development, for example, breast and ovarian cancer, prostate and pancreatic cancer, colorectal cancer, and even childhood tumors like medulloblastoma. Traditionally, patients and families likely to harbor a genetic predisposition have been identified using personal and family history. Several checklists and risk prediction tools have proven to be useful in the clinic. Through the widespread application of next generation sequencing of tumor tissue, a growing number of individuals with genetic cancer predisposition is now identified molecularly, even in the absence of a suggestive family history. Any constitutional variant identified during molecular genetic testing has to be assessed for its relevance, both functionally and in the context of patient phenotype. Variant curation is time consuming, but has been increasingly standardized by introduction of several guidelines to allow reliable and reproducible classification of constitutional variants. Variant classification by expert panels using data mining tools, evidence-based decision trees and gene specific criteria represents the gold standard. Participation of geneticists in molecular tumor boards facilitates the curation of potential constitutional variants, germline validation and thus directing the patient to appropriate counselling and care pathways. Due to the high relevance of germline variants for treatment and surveillance of the index patient and predictive testing and surveillance of relatives, only pathogenic or likely pathogenic variants must be used for clinical decision-making.

Breast cancer risk in BRCA1/2 mutation carriers and noncarriers under prospective intensified surveillance.

Comparably little is known about breast cancer (BC) risks in women from families tested negative for BRCA1/2 mutations despite an indicative family history, as opposed to BRCA1/2 mutation carriers. We determined the age-dependent risks of first and contralateral breast cancer (FBC, CBC) both in noncarriers and carriers of BRCA1/2 mutations, who participated in an intensified breast imaging surveillance program. The study was conducted between January 1, 2005, and September 30, 2017, at 12 university centers of the German Consortium for Hereditary Breast and Ovarian Cancer. Two cohorts were prospectively followed up for incident FBC (n = 4,380; 16,398 person-years [PY], median baseline age: 39 years) and CBC (n = 2,993; 10,090 PY, median baseline age: 42 years). Cumulative FBC risk at age 60 was 61.8% (95% CI 52.8-70.9%) for BRCA1 mutation carriers, 43.2% (95% CI 32.1-56.3%) for BRCA2 mutation carriers and 15.7% (95% CI 11.9-20.4%) for noncarriers. FBC risks were significantly higher than in the general population, with incidence rate ratios of 23.9 (95% CI 18.9-29.8) for BRCA1 mutation carriers, 13.5 (95% CI 9.2-19.1) for BRCA2 mutation carriers and 4.9 (95% CI 3.8-6.3) for BRCA1/2 noncarriers. Cumulative CBC risk 10 years after FBC was 25.1% (95% CI 19.6-31.9%) for BRCA1 mutation carriers, 6.6% (95% CI 3.4-12.5%) for BRCA2 mutation carriers and 3.6% (95% CI 2.2-5.7%) for noncarriers. CBC risk in noncarriers was similar to women with unilateral BC from the general population. Further studies are needed to confirm whether less intensified surveillance is justified in women from BRCA1/2 negative families with elevated risk.

Cancer surveillance and distress among adult pathogenic TP53 germline variant carriers in Germany: A multicenter feasibility and acceptance survey.

BACKGROUND: Li-Fraumeni syndrome (LFS) is a high-risk cancer predisposition syndrome caused by pathogenic germline variants of TP53. Cancer surveillance has noted a significant survival advantage in individuals with LFS; however, little is known about the feasibility, acceptance, and psychosocial effects of such a program. METHODS: Pathogenic TP53 germline variant carriers completed a 7-part questionnaire evaluating sociodemographics, cancer history, surveillance participation, reasons for nonadherence, worries, and distress adapted from the Cancer Worry Scale. Counselees' common concerns and suggestions were assessed in MAXQDA Analytics Pro 12. RESULTS: Forty-nine participants (46 females and 3 males), aged 40.0 ± 12.6 years, formed the study population; 43 (88%) had a personal cancer history (including multiple cancers in 10 [20%]). Forty-three individuals participated (88%) in surveillance during the study or formerly. Willingness to undergo surveillance was influenced by satisfaction with genetic testing and counseling (P = .019 [Fisher-Yates test]) but not by sociodemographics, cancer history, or distress level. Almost one-third of the participants reported logistical difficulties in implementing surveillance because of the high frequency of medical visits, scheduling difficulties, and the travel distance to their surveillance providers. Self-reported distress and perceived emotional burden for family members and partners were moderate (median for self-reported distress, 3.3; median for perceived emotional burden, 3.0). For both, the interquartile range was moderate to very high (2.7-3.7 and 3.0-3.7, respectively). CONCLUSIONS: Individuals with LFS require efficient counseling as well as an accessible, well-organized, interdisciplinary, standardized surveillance program to increase adherence and psychological coping.

Genotypic diversity and phenotypic spectrum of infantile liver failure syndrome type 1 due to variants in LARS1.

PURPOSE: Biallelic variants in LARS1, coding for the cytosolic leucyl-tRNA synthetase, cause infantile liver failure syndrome 1 (ILFS1). Since its description in 2012, there has been no systematic analysis of the clinical spectrum and genetic findings. METHODS: Individuals with biallelic variants in LARS1 were included through an international, multicenter collaboration including novel and previously published patients. Clinical variables were analyzed and functional studies were performed in patient-derived fibroblasts. RESULTS: Twenty-five individuals from 15 families were ascertained including 12 novel patients with eight previously unreported variants. The most prominent clinical findings are recurrent elevation of liver transaminases up to liver failure and encephalopathic episodes, both triggered by febrile illness. Magnetic resonance image (MRI) changes during an encephalopathic episode can be consistent with metabolic stroke. Furthermore, growth retardation, microcytic anemia, neurodevelopmental delay, muscular hypotonia, and infection-related seizures are prevalent. Aminoacylation activity is significantly decreased in all patient cells studied upon temperature elevation in vitro. CONCLUSION: ILFS1 is characterized by recurrent elevation of liver transaminases up to liver failure in conjunction with abnormalities of growth, blood, nervous system, and musculature. Encephalopathic episodes with seizures can occur independently from liver crises and may present with metabolic stroke.

Defining clinical subgroups and genotype-phenotype correlations in NBAS-associated disease across 110 patients.

PURPOSE: Pathogenic variants in neuroblastoma-amplified sequence (NBAS) cause an autosomal recessive disorder with a wide range of symptoms affecting liver, skeletal system, and brain, among others. There is a continuously growing number of patients but a lack of systematic and quantitative analysis. METHODS: Individuals with biallelic variants in NBAS were recruited within an international, multicenter study, including novel and previously published patients. Clinical variables were analyzed with log-linear models and visualized by mosaic plots; facial profiles were investigated via DeepGestalt. The structure of the NBAS protein was predicted using computational methods. RESULTS: One hundred ten individuals from 97 families with biallelic pathogenic NBAS variants were identified, including 26 novel patients with 19 previously unreported variants, giving a total number of 86 variants. Protein modeling redefined the ß-propeller domain of NBAS. Based on the localization of missense variants and in-frame deletions, three clinical subgroups arise that differ significantly regarding main clinical features and are directly related to the affected region of the NBAS protein: ß-propeller (combined phenotype), Sec39 (infantile liver failure syndrome type 2/ILFS2), and C-terminal (short stature, optic atrophy, and Pelger-Huët anomaly/SOPH). CONCLUSION: We define clinical subgroups of NBAS-associated disease that can guide patient management and point to domain-specific functions of NBAS.

What do parents expect from a genetic diagnosis of their child with intellectual disability?

BACKGROUND: Caring for a child with intellectual disability (ID) has been associated with increased social and psychological burdens. Diagnostic and prognostic uncertainty may enhance emotional stress in families. METHOD: The present authors assessed the motivations, expectations, mental health, physical health and the quality of life of 194 parents whose children with intellectual disability were undergoing a genetic diagnostic workup. RESULTS: Most parents considered a diagnosis highly relevant for their own emotional relief, their child's therapies and education, or family planning. Parental mental health was significantly lower compared with the normative sample, but physical health was not different. The severity of the child's intellectual disability correlated negatively with their parents' mental and physical health, quality of life, and positively with parental anxiety. CONCLUSION: Healthcare providers should be aware of the disadvantages facing families with intellectually disabled children. Receiving practical, social and psychological support as well as genetic testing might be particularly relevant for families with severely disabled children.

Biallelic Mutations in NBAS Cause Recurrent Acute Liver Failure with Onset in Infancy.

Acute liver failure (ALF) in infancy and childhood is a life-threatening emergency. Few conditions are known to cause recurrent acute liver failure (RALF), and in about 50% of cases, the underlying molecular cause remains unresolved. Exome sequencing in five unrelated individuals with fever-dependent RALF revealed biallelic mutations in NBAS. Subsequent Sanger sequencing of NBAS in 15 additional unrelated individuals with RALF or ALF identified compound heterozygous mutations in an additional six individuals from five families. Immunoblot analysis of mutant fibroblasts showed reduced protein levels of NBAS and its proposed interaction partner p31, both involved in retrograde transport between endoplasmic reticulum and Golgi. We recommend NBAS analysis in individuals with acute infantile liver failure, especially if triggered by fever.

DDX3X mutations in two girls with a phenotype overlapping Toriello-Carey syndrome.

Recently, de novo heterozygous variants in DDX3X have been reported in about 1.5% of 2659 females with previously unexplained intellectual disability (ID). We report on the identification of DDX3X variants in two unrelated girls with clinical features of Toriello-Carey Syndrome (T-CS). In patient 1, the recurrent variant c.1703C>T; p.(P568L) was identified when reconsidering X-linked de novo heterozygous variants in exome sequencing data. In patient 2, the DDX3X variant c.1600C>G; p.(R534G) was also detected by exome sequencing. Based on these data, de novo heterozygous DDX3X variants should be considered not only in females with unexplained ID, but also in individuals with a clinical diagnosis of T-CS.

Prevalence of BRCA1/2 germline mutations in 21†401 families with breast and ovarian cancer.

PURPOSE: To characterise the prevalence of pathogenic germline mutations in BRCA1 and BRCA2 in families with breast cancer (BC) and ovarian cancer (OC) history. PATIENTS AND METHODS: Data from 21 401 families were gathered between 1996 and 2014 in a clinical setting in the German Consortium for Hereditary Breast and Ovarian Cancer, comprising full pedigrees with cancer status of all individual members at the time of first counselling, and BRCA1/2 mutation status of the index patient. RESULTS: The overall BRCA1/2 mutation prevalence was 24.0% (95% CI 23.4% to 24.6%). Highest mutation frequencies were observed in families with at least two OCs (41.9%, 95% CI 36.1% to 48.0%) and families with at least one breast and one OC (41.6%, 95% CI 40.3% to 43.0%), followed by male BC with at least one female BC or OC (35.8%; 95% CI 32.2% to 39.6%). In families with a single case of early BC (<36 years), mutations were found in 13.7% (95% CI 11.9% to 15.7%). Postmenopausal unilateral or bilateral BC did not increase the probability of mutation detection. Occurrence of premenopausal BC and OC in the same woman led to higher mutation frequencies compared with the occurrence of these two cancers in different individuals (49.0%; 95% CI 41.0% to 57.0% vs 31.5%; 95% CI 28.0% to 35.2%). CONCLUSIONS: Our data provide guidance for healthcare professionals and decision-makers to identify individuals who should undergo genetic testing for hereditary breast and ovarian cancer. Moreover, it supports informed decision-making of counselees on the uptake of genetic testing.

Women at familial risk of breast cancer electing for prophylactic mastectomy: frequencies, procedures, and decision-making characteristics.

BACKGROUND: Some women of families at high risk of breast cancer (BC) choose prophylactic mastectomy (PM) in spite of ambiguous evidence for survival benefits. The aim of this study was to investigate counselees' characteristics, decisions on PM, and frequencies of different procedures to better understand how to tailor interventions. PATIENTS AND METHODS: Eight hundred and forty-nine counselees who attended interdisciplinary consultation for genetic risk adjustment at the University Hospital Heidelberg between July 2009 and July 2011 received a tripartite questionnaire addressing sociodemographic characteristics, psychological parameters, behavioural questions, and medical data. RESULTS: Six hundred and twelve of the 849 counselees (72%) returned the questionnaire. Four hundred were classified as high risk of genetic BC (19.5% BRCA mutation carriers; 4% unclassified variant (UV); and 76.5% calculated as high risk by pedigree). Two hundred and thirteen out of 400 (53%) were diagnosed with BC. Fourteen out of 54 (27%) BRCA mutation carriers with BC chose contralateral PM (CPM) compared to 24/126 (14%) without a mutation but with a personal BC history (p = 0.2175). Of those without BC, 12/27 (44%) mutation carriers opted for bilateral PM (BPM) compared to none without a mutation (p < 0.0001). Women who received any PM (CPM and BPM) reported a higher emotional burden from partners (p = 0.003) and family (p = 0.008), more worries regarding children and family (p = 0.003) and were associated with positive mutation status and higher heterozygous and lifetime risk (all p < 0.001). CONCLUSION: Although evidence on survival benefit is unclear in several clinical situations, a relevant number of counselees opt for PM. Counselees may decide based on other reasons than survival benefit.

Adherence to the breast cancer surveillance program for women at risk for familial breast and ovarian cancer versus overscreening: a monocenter study in Germany.

Breast cancer (BC) is the leading cancer among women worldwide and in 5-10 % of cases is of hereditary origin, mainly due to BRCA1/2 mutations. Therefore, the German Consortium for Familial Breast and Ovarian Cancer (HBOC) with its 15 specialized academic centers offers families at high risk for familial/hereditary cancer a multimodal breast cancer surveillance program (MBCS) with regular breast MRI, mammography, ultrasound, and palpation. So far, we know a lot about the psychological effects of genetic testing, but we know little about risk-correlated adherence to MBCS or prophylactic surgery over time. The aim of this study was to investigate counselees' adherence to recommendations for MBCS in order to adjust the care supply and define predictors for incompliance. All counselees, who attended HBOC consultation at the University Hospital Heidelberg between July 01, 2009 and July 01, 2011 were eligible to participate. A tripartite questionnaire containing sociodemographic information, psychological parameters, behavioral questions, and medical data collection from the German consortium were used. A high participation rate was achieved among the study population, with 72 % returning the questionnaire. This study showed a rate of 59 % of full-adherers to the MBCS. Significant predictors for partial or full adherence were having children (p = 0.0221), younger daughters (p = 0.01795), a higher awareness of the topic HBOC (p = 0.01795, p < 0.0001), a higher perceived breast cancer risk (p < 0.0001), and worries (p = 0.0008)/impairment (p = 0.0257) by it. Although the current data suggest a good adherence of MBCS, prospective studies are needed to understand counselees' needs to further improve surveillance programs and adherence to them. Adherence to the breast cancer surveillance program for women at risk for familial breast and ovarian cancer versus overscreening-a monocenter study in Germany.

Recurrent acute liver failure due to NBAS deficiency: phenotypic spectrum, disease mechanisms, and therapeutic concepts.

BACKGROUND: Acute liver failure (ALF) in infancy and childhood is a life-threatening emergency and in about 50% the etiology remains unknown. Recently biallelic mutations in NBAS were identified as a new molecular cause of ALF with onset in infancy, leading to recurrent acute liver failure (RALF). METHODS: The phenotype and medical history of 14 individuals with NBAS deficiency was studied in detail and functional studies were performed on patients' fibroblasts. RESULTS: The phenotypic spectrum of NBAS deficiency ranges from isolated RALF to a multisystemic disease with short stature, skeletal dysplasia, immunological abnormalities, optic atrophy, and normal motor and cognitive development resembling SOPH syndrome. Liver crises are triggered by febrile infections; they become less frequent with age but are not restricted to childhood. Complete recovery is typical, but ALF crises can be fatal. Antipyretic therapy and induction of anabolism including glucose and parenteral lipids effectively ameliorates the course of liver crises. Patients' fibroblasts showed an increased sensitivity to high temperature at protein and functional level and a disturbed tethering of vesicles, pointing at a defect of intracellular transport between the endoplasmic reticulum and Golgi. CONCLUSIONS: Mutations in NBAS cause a complex disease with a wide clinical spectrum ranging from isolated RALF to a multisystemic phenotype. Thermal susceptibility of the syntaxin 18 complex is the basis of fever dependency of ALF episodes. NBAS deficiency is the first disease related to a primary defect of retrograde transport. Identification of NBAS deficiency allows optimized therapy of liver crises and even prevention of further episodes.

Long-term experiences with genetic consultation in people with hereditary breast and ovarian cancer.

PURPOSE: Advances in genetics and increased public awareness increased the demand for interdisciplinary genetic outpatient consultation (IOGC). Communicating cancer risk is complex, and ideally information transfer should be individualized. Although psychological experiences with genetic testing have been studied in detail, studies on long-term experiences with IOGC and information transfer are lacking. We assessed patients' understanding and satisfaction with IOGC in families at risk of hereditary breast and ovarian cancer (HBOC) with the aim of informing best clinical practice, improving compliance and informed decision-making. METHODS: Female counselees referred for IOGC between July 1, 2009 and July 1, 2011 were eligible. Data were collected using a 47-item postal questionnaire to assess sociodemographic, psychological, behavioral parameters. Overall satisfaction and personal usefulness of IOGC were assessed with a five-point, and risk perception with a visual analog scale. Data were analyzed using Spearman rank, Wilcoxon U or Chi-squared test. RESULTS: 612 (72 %) of 849 women participated reported being highly satisfied (75 %, n = 430) and declared personal usefulness (73 %, n = 421) on average 3.5 years after IOGC. Women deemed "high risk" assessed their risk of developing BC as significantly higher than non-high-risk counselees (3.2 versus 3.0, p = 0.00484). Risk perception was lower in BRCA1/2 mutation carriers than in women with unclassified variants or no mutation (2.8 versus 3.5 and 3.1, respectively). CONCLUSION: Women with an HBOC background have additional needs to achieve long-term satisfaction after IOGC. Prospective studies are required to optimize care for the increasing number of people who seek genetic consultation, particularly as the complexity of genetics knowledge increases.

A mutation in the FAM36A gene, the human ortholog of COX20, impairs cytochrome c oxidase assembly and is associated with ataxia and muscle hypotonia.

The mitochondrial respiratory chain complex IV (cytochrome c oxidase) is a multi-subunit enzyme that transfers electrons from cytochrome c to molecular oxygen, yielding water. Its biogenesis requires concerted expression of mitochondria- and nuclear-encoded subunits and assembly factors. In this report, we describe a homozygous missense mutation in FAM36A from a patient who displays ataxia and muscle hypotonia. The FAM36A gene is a remote, putative ortholog of the fungal complex IV assembly factor COX20. Messenger RNA (mRNA) and protein co-expression analyses support the involvement of FAM36A in complex IV function in mammals. The c.154A>C mutation in the FAM36A gene, a mutation that is absent in sequenced exomes, leads to a reduced activity and lower levels of complex IV and its protein subunits. The FAM36A protein is nearly absent in patient's fibroblasts. Cells affected by the mutation accumulate subassemblies of complex IV that contain COX1 but are almost devoid of COX2 protein. We observe co-purification of FAM36A and COX2 proteins, supporting that the FAM36A defect hampers the early step of complex IV assembly at the incorporation of the COX2 subunit. Lentiviral complementation of patient's fibroblasts with wild-type FAM36A increases the complex IV activity as well as the amount of holocomplex IV and of individual subunits. These results establish the function of the human gene FAM36A/COX20 in complex IV assembly and support a causal role of the gene in complex IV deficiency.

Clinical and molecular characterization of the BRCA2 p.Asn3124Ile variant reveals substantial evidence for pathogenic significance.

Variants of uncertain clinical significance (VUS) in the high-penetrance breast cancer susceptibility genes BRCA1 and BRCA2 represent a major obstacle in genetic counseling of high-risk breast cancer families. We analyzed a missense VUS located in BRCA2 (p.Asn3124Ile; HGVS: BRCA2 c.9371A > T) present in seven independent high-risk breast cancer families that were counseled and genetically tested in South-West Germany. The VUS was identified by DNA sequencing. We analyzed co-occurrence with deleterious BRCA1/2 mutations, segregation, evolutionary conservation, in silico impact prediction, and prevalence in the general population. All carriers of the VUS suffered from breast or ovarian cancer. In two families, an additional high burden of other cancers such as pancreatic, prostate, and gastric cancers was reported, one further family included two cases of male breast cancer. The VUS did not co-occur with deleterious BRCA1/2 mutations and segregated in two affected individuals of one family. In contrast to the 7/1,347 (0,5 %) tested high-risk BC families without clearly pathogenic mutations in BRCA1/2, none of 3,126 healthy population controls sharing the same ethnic and geographical background were found to carry this VUS (p = 0.0002). In-silico prediction revealed strong evolutionary conservation of the asparagine residue, residing in the C-terminal oligonucleotide-binding-fold-3 region, and a most likely damaging impact of this exchange on the protein structure. The BRCA2 p.Asn3124Ile (BRCA2 c.9371A > T) variant is a rare mutation with a damaging effect on the BRCA2 protein that is strongly associated with familial breast and ovarian cancer risk, indicating its most likely pathogenic nature and clinical relevance.