Expedited evaluation of hereditary hematopoietic malignancies in the setting of stem cell transplantation.

Not available.

A novel telomere biology disease-associated gastritis identified through a whole exome sequencing-driven approach.

A whole exome sequencing (WES)-driven approach to uncover the etiology of unexplained inflammatory gastritides has been underutilized by surgical pathologists. Here, we discovered the pathobiology of an unusual chronic atrophic gastritis in two unrelated patients using this approach. The gastric biopsies were notable for an unusual pattern of gastritis with persistent dense inflammation, loss of both parietal and neuroendocrine cells in the oxyntic mucosa, and sparing of the antral mucosa. The patients were found to harbor pathogenic variants in telomeropathic genes (POT1 and DCLRE1B). Clonality testing for one of the patients showed evidence of evolving clonality of TCR-gene rearrangement. Both patients showed significantly decreased numbers of stem/progenitor cells by immunohistochemistry, which appears to be responsible for the development of mucosal atrophy. No such cases of unusual chronic atrophic gastritis in the setting of telomeropathy have been previously reported. The loss of stem/progenitor cells suggests that stem/progenitor cell exhaustion in the setting of telomere dysfunction is the likely mechanism for development of this unusual chronic atrophic gastritis. The results underscore the need for close monitoring of these gastric lesions, with special regard to their neoplastic potential. This combined WES-driven approach has promise to identify the cause and mechanism of other uncharacterized gastrointestinal inflammatory disorders.

Germline Variants Incidentally Detected via Tumor-Only Genomic Profiling of Patients With Mesothelioma.

Importance: Patients with mesothelioma often have next-generation sequencing (NGS) of their tumor performed; tumor-only NGS may incidentally identify germline pathogenic or likely pathogenic (P/LP) variants despite not being designed for this purpose. It is unknown how frequently patients with mesothelioma have germline P/LP variants incidentally detected via tumor-only NGS. Objective: To determine the prevalence of incidental germline P/LP variants detected via tumor-only NGS of mesothelioma. Design, Setting, and Participants: A series of 161 unrelated patients with mesothelioma from a high-volume mesothelioma program had tumor-only and germline NGS performed during April 2016 to October 2021. Follow-up ranged from 18 months to 7 years. Tumor and germline assays were compared to determine which P/LP variants identified via tumor-only NGS were of germline origin. Data were analyzed from January to March 2023. Main Outcomes and Measures: The proportion of patients with mesothelioma who had P/LP germline variants incidentally detected via tumor-only NGS. Results: Of 161 patients with mesothelioma, 105 were male (65%), the mean (SD) age was 64.7 (11.2) years, and 156 patients (97%) self-identified as non-Hispanic White. Most (126 patients [78%]) had at least 1 potentially incidental P/LP germline variant. The positive predictive value of a potentially incidental germline P/LP variant on tumor-only NGS was 20%. Overall, 26 patients (16%) carried a P/LP germline variant. Germline P/LP variants were identified in ATM, ATR, BAP1, CHEK2, DDX41, FANCM, HAX1, MRE11A, MSH6, MUTYH, NF1, SAMD9L, and TMEM127. Conclusions and Relevance: In this case series of 161 patients with mesothelioma, 16% had confirmed germline P/LP variants. Given the implications of a hereditary cancer syndrome diagnosis for preventive care and familial counseling, clinical approaches for addressing incidental P/LP germline variants in tumor-only NGS are needed. Tumor-only sequencing should not replace dedicated germline testing. Universal germline testing is likely needed for patients with mesothelioma.

The landscape of reported VUS in multi-gene panel and genomic testing: Time for a change.

PURPOSE: Variants of uncertain significance (VUS) are a common result of diagnostic genetic testing and can be difficult to manage with potential misinterpretation and downstream costs, including time investment by clinicians. We investigated the rate of VUS reported on diagnostic testing via multi-gene panels (MGPs) and exome and genome sequencing (ES/GS) to measure the magnitude of uncertain results and explore ways to reduce their potentially detrimental impact. METHODS: Rates of inconclusive results due to VUS were collected from over 1.5 million sequencing test results from 19 clinical laboratories in North America from 2020 to 2021. RESULTS: We found a lower rate of inconclusive test results due to VUSs from ES/GS (22.5%) compared with MGPs (32.6%; P < .0001). For MGPs, the rate of inconclusive results correlated with panel size. The use of trios reduced inconclusive rates (18.9% vs 27.6%; P < .0001), whereas the use of GS compared with ES had no impact (22.2% vs 22.6%; P = ns). CONCLUSION: The high rate of VUS observed in diagnostic MGP testing warrants examining current variant reporting practices. We propose several approaches to reduce reported VUS rates, while directing clinician resources toward important VUS follow-up.

Exome sequencing identifies PD-L2 as a potential predisposition gene for lymphoma.

To investigate germline predisposition in lymphoma, we performed whole-exome sequencing and discovered a novel variant (c.817-1G>T) in programmed cell death 1 ligand 2 (PD-L2) in a family with early-onset lymphomas and other cancers. The variant was present in the proband with follicular lymphoma and his son with Hodgkin's lymphoma. It was in the terminal splice acceptor site of PD-L2 and embedded in a putative enhancer of Janus kinase 2 (JAK2) and programmed cell death 1 ligand (PD-L1). We also found that gene expression of PD-L2, PD-L1, and JAK2 was significantly increased. Using 3' rapid amplification of cDNA ends (3' RACE), we detected an abnormal PD-L2 transcript in the son. Thus, the c.817-1G>T variant may result in the elevated PD-L2 expression due to the abnormal PD-L2 transcript and the elevated PD-L1 and JAK2 expression due to increased enhancer activity of PD-L1 and JAK2. The PD-L2 novel variant likely underlies the genetic etiology of the lymphomas in the family. As PD-L2 plays critical roles in tumor immunity, identification of PD-L2 as a germline predisposition gene may inform personalized immunotherapy in lymphoma patients.

Feasibility and limitations of cultured skin fibroblasts for germline genetic testing in hematologic disorders.

To avoid acquired variants found in the blood, cultured skin fibroblasts are a recommended DNA source for germline genetic testing in patients with hematologic disorders, but data are lacking regarding practicality and limitations. We conducted a retrospective cohort study of 350 subjects with hematologic disorders who underwent skin fibroblast culture for germline genetic testing. We analyzed next-generation sequencing data from the targeted capture of 144 inherited cancer and bonemarrow failure genes to identify variants at heterozygous and subclonal variant allele frequencies. Sixteen (5%) biopsies failed to culture. Culture failure was more likely in samples with delays in culture initiation (OR = 4.3; p < 0.01) or a pathogenic variant in a telomere gene (OR = 42.6; p < 0.01). Median culture time was 28 days (IQR 22-29 days). Culture time was longer for subjects with prior allogeneic stem cell transplantation (+10.7%; p = 0.02) and shorter in subjects with a heterozygous pathogenic variant (-11.9%; p < 0.01), larger biopsy size (-10.6%; p < 0.01), or lymphoid malignancy (-8.4%; p < 0.01). Subclonal variants were identified in 10 (4%) and confirmed in five (56%) of eight with alternate samples available. Subclonal and discordant variants illustrate that germline testing from cultured skin fibroblasts requires phenotypic correlation and, in rare cases, follow-up studies for optimal interpretation.

Novel KDM6A Kabuki Syndrome Mutation With Hyperinsulinemic Hypoglycemia and Pulmonary Hypertension Requiring ECMO.

Kabuki syndrome (KS) is a multisystem disorder estimated to occur in 1:32 000 newborns. Pathogenic mutations cause the majority but not all cases of KS in either KMT2D or KDM6A. KS can be suspected by phenotypic features, including infantile hypotonia, developmental delay, dysmorphic features, congenital heart defects, and others. Still, many of these features are not readily apparent in a newborn. Although neonatal hypoglycemia has been reported in 8% to 10% of patients with KS, the incidence and severity of hyperinsulinemic hypoglycemia (HH) is not well-studied. We present a full-term female infant with HH who was responsive to low-dose diazoxide. At 3 months of age, she was admitted for septic shock, worsening respiratory status, and severe pulmonary hypertension, requiring extracorporeal membrane oxygenation support. Her neonatal history was notable for hypotonia, dysphagia with aspiration requiring gastrostomy tube placement, and a cardiac defect-hypoplastic aortic arch requiring aortic arch repair. She has characteristic facial features, including prominent eyelashes, long palpebral fissures, and a short nasal columella. Next-generation sequencing for HH revealed a de novo likely pathogenic missense variant in KDM6A gene: c.3479G > T, p.Gly1160Val that was absent from population databases. Genetic testing for causes of HH should include testing of the KS genes KMT2D and KDM6A. Early detection of the underlying genetic defect will help guide management as all reported HH cases associated with KS have been responsive to diazoxide. Affected infants with underlying cardiac conditions may be at higher risk of serious respiratory complications such as pulmonary hypertension.

Novel compound heterozygous LRBA deletions in a 6-month-old with neonatal diabetes.

We report a 6-month-old boy with antibody-positive insulin-dependent diabetes mellitus. Sequencing identified compound heterozygous deletions of exon 5 and exons 36-37 in LRBA. At three years, he has yet to exhibit any other immune symptoms. Genetic testing of LRBA is warranted in patients with neonatal diabetes, even without immune dysregulation.

Further delineation of a recognizable type of syndromic short stature caused by biallelic SEMA3A loss-of-function variants.

The semaphorin protein family is a diverse set of extracellular signaling proteins that perform fundamental roles in the development and operation of numerous biological systems, notably the nervous, musculoskeletal, cardiovascular, endocrine, and reproductive systems. Recently, recessive loss-of-function (LoF) variants in SEMA3A (semaphorin 3A) have been shown to result in a recognizable syndrome characterized by short stature, skeletal abnormalities, congenital heart defects, and variable additional anomalies. Here, we describe the clinical and molecular characterization of a female patient presenting with skeletal dysplasia, hypogonadotropic hypogonadism (HH), and anosmia who harbors a nonsense variant c.1633C>T (p.Arg555*) and a deletion of exons 15, 16, and 17 in SEMA3A in the compound heterozygous state. These variants were identified through next-generation sequencing analysis of a panel of 26 genes known to be associated with HH/Kallmann syndrome. Our findings further substantiate the notion that biallelic LoF SEMA3A variants cause a syndromic form of short stature and expand the phenotypic spectrum associated with this condition to include features of Kallmann syndrome.

Telomere biology disorder prevalence and phenotypes in adults with familial hematologic and/or pulmonary presentations.

Telomere biology disorders (TBDs) present heterogeneously, ranging from infantile bone marrow failure associated with very short telomeres to adult-onset interstitial lung disease (ILD) with normal telomere length. Yield of genetic testing and phenotypic spectra for TBDs caused by the expanding list of telomere genes in adults remain understudied. Thus, we screened adults aged ≥18 years with a personal and/or family history clustering hematologic disorders and/or ILD enrolled on The University of Chicago Inherited Hematologic Disorders Registry for causative variants in 13 TBD genes. Sixteen (10%) of 153 probands carried causative variants distributed among TERT (n = 6), TERC (n = 4), PARN (n = 5), or RTEL1 (n = 1), of which 19% were copy number variants. The highest yield (9 of 22 [41%]) was in families with mixed hematologic and ILD presentations, suggesting that ILD in hematology populations and hematologic abnormalities in ILD populations warrant TBD genetic testing. Four (3%) of 117 familial hematologic disorder families without ILD carried TBD variants, making TBD second to only DDX41 in frequency for genetic diagnoses in this population. Phenotypes of 17 carriers with heterozygous PARN variants included 4 (24%) with hematologic abnormalities, 67% with lymphocyte telomere lengths measured by flow cytometry and fluorescence in situ hybridization at or above the 10th percentile, and a high penetrance for ILD. Alternative etiologies for cytopenias and/or ILD such as autoimmune features were noted in multiple TBD families, emphasizing the need to maintain clinical suspicion for a TBD despite the presence of alternative explanations.

CFTR variant testing: a technical standard of the American College of Medical Genetics and Genomics (ACMG).

Pathogenic variants in the CFTR gene are causative of classic cystic fibrosis (CF) as well as some nonclassic CF phenotypes. In 2001, CF became the first target of pan-ethnic universal carrier screening by molecular methods. The American College of Medical Genetics and Genomics (ACMG) recommended a core panel of 23 disease-causing variants as the minimal set to be included in pan-ethnic carrier screening of individuals with no family history of the disease, and these variants were usually assessed using targeted methods. The original recommendation also left open the option for laboratories to offer expanded CFTR variant panels; however, at the time, expanded CFTR variant panels were met with some controversy on the basis of the available technologies and the limited phenotypic knowledge of rare variants. Both of those aspects have now evolved, prompting this update of the ACMG technical standards for CFTR variant testing.

De Novo Variants in SPOP Cause Two Clinically Distinct Neurodevelopmental Disorders.

Recurrent somatic variants in SPOP are cancer specific; endometrial and prostate cancers result from gain-of-function and dominant-negative effects toward BET proteins, respectively. By using clinical exome sequencing, we identified six de novo pathogenic missense variants in SPOP in seven individuals with developmental delay and/or intellectual disability, facial dysmorphisms, and congenital anomalies. Two individuals shared craniofacial dysmorphisms, including congenital microcephaly, that were strikingly different from those of the other five individuals, who had (relative) macrocephaly and hypertelorism. We measured the effect of SPOP variants on BET protein amounts in human Ishikawa endometrial cancer cells and patient-derived cell lines because we hypothesized that variants would lead to functional divergent effects on BET proteins. The de novo variants c.362G>A (p.Arg121Gln) and c. 430G>A (p.Asp144Asn), identified in the first two individuals, resulted in a gain of function, and conversely, the c.73A>G (p.Thr25Ala), c.248A>G (p.Tyr83Cys), c.395G>T (p.Gly132Val), and c.412C>T (p.Arg138Cys) variants resulted in a dominant-negative effect. Our findings suggest that these opposite functional effects caused by the variants in SPOP result in two distinct and clinically recognizable syndromic forms of intellectual disability with contrasting craniofacial dysmorphisms.

Update of variants identified in the pancreatic ß-cell KATP channel genes KCNJ11 and ABCC8 in individuals with congenital hyperinsulinism and diabetes.

The most common genetic cause of neonatal diabetes and hyperinsulinism is pathogenic variants in ABCC8 and KCNJ11. These genes encode the subunits of the ß-cell ATP-sensitive potassium channel, a key component of the glucose-stimulated insulin secretion pathway. Mutations in the two genes cause dysregulated insulin secretion; inactivating mutations cause an oversecretion of insulin, leading to congenital hyperinsulinism, whereas activating mutations cause the opposing phenotype, diabetes. This review focuses on variants identified in ABCC8 and KCNJ11, the phenotypic spectrum and the treatment implications for individuals with pathogenic variants.

Adapting ACMG/AMP sequence variant classification guidelines for single-gene copy number variants.

PURPOSE: The ability of a single technology, next-generation sequencing, to provide both sequence and copy number variant (CNV) results has driven the merger of clinical cytogenetics and molecular genetics. Consequently, the distinction between the definition of a sequence variant and a CNV is blurry. As the 2015 American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) standards and guidelines for interpretation of sequence variants address CNV classification only sparingly, this study focused on adapting ACMG/AMP criteria for single-gene CNV interpretation. METHODS: CNV-specific modifications of the 2015 ACMG/AMP criteria were developed and their utility was independently tested by three diagnostic laboratories. Each laboratory team interpreted the same 12 single-gene CNVs using three systems: (1) without ACMG/AMP guidance, (2) with ACMG/AMP criteria, and (3) with new modifications. A replication study of 12 different CNVs validated the modified criteria. RESULTS: The adapted criteria system presented here showed improved concordance and usability for single-gene CNVs compared with using the ACMG/AMP interpretation guidelines focused on sequence variants. CONCLUSION: These single-gene CNV criteria modifications could be used as a supplement to the ACMG/AMP guidelines for sequence variants, allowing for a streamlined workflow and a step toward a uniform classification system for both sequence and copy number alterations.

Correction: Adapting ACMG/AMP sequence variant classification guidelines for single-gene copy-number variants.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

GCK-MODY in the US Monogenic Diabetes Registry: Description of 27 unpublished variants.

We report on 134 unique GCK variants in 217 families, including 27 unpublished variants, identified in the US Monogenic Diabetes Registry in the last decade. Using ACMG guidelines, 26% were pathogenic, 56% likely pathogenic and 18% were of uncertain significance. Those with pathogenic variants had clinical features consistent with GCK-MODY.

Congenital hyperinsulinism as the presenting feature of Kabuki syndrome: clinical and molecular characterization of 9 affected individuals.

PURPOSE: Describe the clinical and molecular findings of patients with Kabuki syndrome (KS) who present with hypoglycemia due to congenital hyperinsulinism (HI), and assess the incidence of KS in patients with HI. METHODS: We documented the clinical features and molecular diagnoses of 9 infants with persistent HI and KS via a combination of sequencing and copy-number profiling methodologies. Subsequently, we retrospectively evaluated 100 infants with HI lacking a genetic diagnosis, for causative variants in KS genes. RESULTS: Molecular diagnoses of KS were established by identification of pathogenic variants in KMT2D (n = 5) and KDM6A (n = 4). Among the 100 infants with HI of unknown genetic etiology, a KS diagnosis was uncovered in one patient. CONCLUSIONS: The incidence of HI among patients with KS may be higher than previously reported, and KS may account for as much as 1% of patients diagnosed with HI. As the recognition of dysmorphic features associated with KS is challenging in the neonatal period, we propose KS should be considered in the differential diagnosis of HI. Since HI in patients with KS is well managed medically, a timely recognition of hyperinsulinemic episodes will improve outcomes, and prevent aggravation of the preexisting mild to moderate intellectual disability in KS.

Targeted exome analysis identifies the genetic basis of disease in over 50% of patients with a wide range of ataxia-related phenotypes.

PURPOSE: To examine the impact of a targeted exome approach for the molecular diagnosis of patients nationwide with a wide range of ataxia-related phenotypes. METHODS: One hundred and seventy patients with ataxia of unknown etiology referred from clinics throughout the United States and Canada were studied using a targeted exome approach. Patients ranged in age from 2 to 88 years. Analysis was focused on 441 curated genes associated with ataxia and ataxia-like conditions. RESULTS: Pathogenic and suspected diagnostic variants were identified in 88 of the 170 patients, providing a positive molecular diagnostic rate of 52%. Forty-six different genes were implicated, with the six most commonly mutated genes being SPG7, SYNE1, ADCK3, CACNA1A, ATP1A3, and SPTBN2, which accounted for >40% of the positive cases. In many cases a diagnosis was provided for conditions that were not suspected and resulted in the broadening of the clinical spectrum of several conditions. CONCLUSION: Exome sequencing with targeted analysis provides a high-yield approach for the genetic diagnosis of ataxia-related conditions. This is the largest targeted exome study performed to date in patients with ataxia and ataxia-like conditions and represents patients with a wide range of ataxia phenotypes typically encountered in neurology and genetics clinics.