Common epilepsy variants from the general population are not associated with epilepsy among individuals with tuberous sclerosis complex.

Common genetic variants identified in the general population have been found to increase phenotypic risks among individuals with certain genetic conditions. Up to 90% of individuals with tuberous sclerosis complex (TSC) are affected by some type of epilepsy, yet the common variants contributing to epilepsy risk in the general population have not been evaluated in the context of TSC-associated epilepsy. Such knowledge is important to help uncover the underlying pathogenesis of epilepsy in TSC which is not fully understood, and critical as uncontrolled epilepsy is a major problem in this population. To evaluate common genetic modifiers of epilepsy, our study pooled phenotypic and genotypic data from 369 individuals with TSC to evaluate known and novel epilepsy common variants. We did not find evidence of enhanced genetic penetrance for known epilepsy variants identified across the largest genome-wide association studies of epilepsy in the general population, but identified support for novel common epilepsy variants in the context of TSC. Specifically, we have identified a novel signal in SLC7A1 that may be functionally involved in pathways relevant to TSC and epilepsy. Our study highlights the need for further evaluation of genetic modifiers in TSC to aid in further understanding of epilepsy in TSC and improve outcomes.

Arginase deficiency masked by cerebral palsy and coagulopathy-Three varied presentations of Latin American origin.

Arginase deficiency (ARG1-D) is an autosomal recessive inborn error of metabolism that is often misdiagnosed. Classic presentation of ARG1-D includes progressive symptoms of spasticity, delayed development, cognitive impairment, protein avoidance, and seizures. Patients who present atypically may evade diagnosis and require a thoughtful diagnostic workup. Here, we discuss three females of Latin American origin with differing clinical presentations, but who all have the same intronic pathogenic variant in ARG1. Importantly, we found that each case included elevated coagulopathy on laboratory testing and discussed one case in particular with manifestation of bleeding. When diagnosed early, treatment is favorable and can prevent progressive decline. While many states have added ARG1-D to their expanded newborn screening panels, still many states and countries do not screen for ARG1-D, and it can be missed in a healthy newborn. We aim to bring awareness to not only the classic presentation as a necessary consideration for otherwise unexplained spastic diplegia but also to the varied presentations of ARG1-D.

Mild TSC phenotype and non-penetrance associated with a frameshift variant in TSC2 prompts caution in evaluating pathogenicity of frameshift variants.

INTRODUCTION: Technological advances in genetic testing, particularly the adoption of noninvasive prenatal screening (NIPS) for single gene disorders such as tuberous sclerosis complex (TSC, OMIM# 613254), mean that putative/possible pathogenetic DNA variants can be identified prior to the appearance of a disease phenotype. Without a phenotype, accurate prediction of variant pathogenicity is crucial. Here, we report a TSC2 frameshift variant, NM_000548.5(TSC2):c.4255_4256delCA, predicted to result in nonsense-mediated mRNA decay (NMD) and cessation of TSC2 protein production and thus pathogenic according to ACMG criteria, identified by NIPS and subsequently detected in family members with few or no symptoms of TSC. Due to the lack of TSC-associated features in the family, we hypothesized that the deletion created a non-canonical 5' donor site resulting in cryptic splicing and a transcript encoding active TSC2 protein. Verifying the predicted effect of the variant was key to designating pathogenicity in this case and should be considered for other frameshift variants in other genetic disorders. METHODS: Phenotypic information on the family members was collected via review of the medical records and patient reports. RNA studies were performed using proband mRNA isolated from blood lymphocytes for RT-PCR and Sanger sequencing. Functional studies were performed by transient expression of the TSC2 variant proteins in cultured cells, followed by immunoblotting. RESULTS: No family members harboring the variant met any major clinical diagnostic criteria for TSC, though a few minor features non-specific to TSC were present. RNA studies supported the hypothesis that the variant caused cryptic splicing, resulting in an mRNA transcript with an in-frame deletion of 93 base pairs r.[4255_4256del, 4251_4343del], p.[(Gln1419Valfs*104), (Gln1419_Ser1449del)]. Expression studies demonstrated that the canonical function of the resulting truncated TSC2 p.Gln1419_Ser1449del protein product was maintained and similar to wildtype. CONCLUSION: Although most frameshift variants are likely to result in NMD, the NM_000548.5(TSC2):c.4255_4256delCA variant creates a cryptic 5' splice donor site, resulting in an in-frame deletion that retains TSC2 function, explaining why carriers of the variant do not have typical features of TSC. The information is important for this family and others with the same variant. Equally important is the lesson that predictions can be inaccurate, and that caution should be used when designating frameshift variants as pathogenic, especially when phenotypic information to corroborate testing results is unavailable. Our work demonstrates that functional RNA- and protein-based confirmation of the effects of DNA variants improves molecular genetic diagnostics.

Assessing patient attitudes toward genetic testing for hereditary hematologic malignancy.

Since 2003, more than 15 genes have been identified to predispose to hereditary hematologic malignancy (HHM). Although the yield of germline analysis for leukemia appears like that of solid tumors, genetic referrals in adults with leukemia remain underperformed. We assessed leukemia patients' attitudes toward genetic testing and leukemia-related distress through a survey of 1093 patients diagnosed with acute or chronic leukemia, myelodysplastic syndrome, or aplastic anemia. Principal component analysis (PCA) was used to analyze patient attitudes. Distress was measured through the Impact of Event Scale-Revised (IES-R). Exactly 19.8% of eligible respondents completed the survey. The majority reported interest in (77%) or choosing to have (78%) genetic testing for HHM. Slightly over half identified worry about cost of genetic testing (58%) or health insurance coverage (61%) as possible barriers. PCA identified relevant themes of interest in genetic testing, impact on leukemia treatment, discrimination and confidentiality, psychosocial and familial impacts, and cost of testing. The majority reported low distress. Leukemia patients report high interest in genetic testing, few barriers, and relatively low distress.

Case Report: Novel pathogenic variant in NFIX in two sisters with Malan syndrome due to germline mosaicism.

Malan syndrome is an autosomal dominant disorder caused by pathogenic variants in NFIX with less than 100 cases reported thus far. NFIX is important for stem cell proliferation, quiescence, and differentiation during development and its protein plays a role in replication, signal transduction, and transcription. As a result of pathogenic variants, symptoms of Malan syndrome include overgrowth, intellectual disability, speech delay, and dysmorphic features. Currently, the recurrence risk for this disorder is indicated at less than 1%, standard for de novo autosomal dominant disorders. Herein, we report an additional set of sisters with the same novel pathogenic variant in NFIX and clinical features consistent with Malan syndrome providing evidence of germline mosaicism. Considering the rarity of this condition in conjunction with three previous reports of germline mosaicism, it is worthwhile to investigate and re-evaluate the proper recurrence risk for this condition. This discovery would be paramount for family planning and genetic counseling practices in families with affected individuals.

NEXMIF pathogenic variants in individuals of Korean, Vietnamese, and Mexican descent.

NEXMIF pathogenic variants have been known to produce a wide spectrum of X-linked intellectual disability (ID) in both males and females. Thus far, few individuals from diverse populations have been described with NEXMIF-related disorders. Herein, we report three individuals with NEXMIF pathogenic variants, the first two are the only males of Korean and Vietnamese descent described with this disorder to our knowledge. The last patient is a Hispanic female who harbors the same pathogenic variant as a previously described Caucasian individual, but with differing clinical presentation. These patients present with many classic symptoms of NEXMIF-related disorders including ID, epilepsy, developmental delay, and dysmorphic features. In addition, they have symptoms that have not been thoroughly described in the literature, including allergies with multiple anaphylactic events and hypothyroidism. This report is intended to raise awareness and educate about the clinical signs that may prompt testing for NEXMIF-related disorders.

Massive macroglossia, a rare side effect of COVID-19: clinical, histologic, and genomic findings in COVID-19-positive versus COVID-19-negative patients.

PURPOSE: The primary purpose of this study is to identify if there is an underlying genetic predisposition for COVID-related macroglossia and if this susceptibility is higher among individuals of African heritage. Secondary objectives include determining if genetic testing of COVID-infected patients who are intubated and prone could identify patients with higher susceptibility to the development of macroglossia. METHODS: A retrospective chart review was completed for each patient, and prospectively, genetic and histopathologic analyses were completed. Whole-exome sequencing was completed on two patients; immunohistochemistry was completed on the COVID-positive tissue samples. RESULTS: Histopathology of the COVID-positive patient revealed significant peri-lymphocytic infiltrate, which was absent in the COVID-negative patient. Immunohistochemistry confirmed the presence of immune cells. Results from the whole-exome sequencing were inconclusive. CONCLUSION: The findings of this study are consistent with others that have observed a lymphocytic infiltrate in the organs of patients infected with SARS-CoV-2. On histology, IHC highlighted a CD45 + predominance, indicating that a robust immune response is present in the tissues. The pathobiology of this phenomenon and its role in the development and/or persistence of massive macroglossia requires further study.

Exploring the predicted yield of prenatal testing by evaluating a postnatal population with structural abnormalities using a novel mathematical model.

OBJECTIVE: To determine the yield of prenatal testing and screening options after identification of fetal structural abnormalities using a novel mathematical model. METHOD: A retrospective chart review was conducted to collect structural abnormality and genetic testing data on infants who were evaluated postnatally by a medical geneticist. A novel mathematical model was used to determine and compare the predicted diagnostic yields of prenatal testing and screening options. RESULTS: Over a quarter of patients with at least one structural abnormality (28.1%, n = 222) had a genetic aberration identified that explained their phenotype. Chromosomal microarray (CMA) had the highest predicted diagnostic yield (26.8%, P < .001). Karyotype (20.8%) had similar yields as genome wide NIPT (21.2%, P = .859) and NIPT with select copy number variants (CNVs) (17.9%, P = .184). Among individuals with an isolated structural abnormality, whole exome sequencing (25.9%) and CMA (14.9%) had the highest predicted yields. CONCLUSION: This study introduces a novel mathematical model for predicting the potential yield of prenatal testing and screening options. This study provides further evidence that CMA has the highest predicted diagnostic yield in cases with structural abnormalities. Screening with expanded NIPT options shows potential for patients who decline invasive testing, but only in the setting of adequate pre-test counseling.

Epilepsy Risk Prediction Model for Patients With Tuberous Sclerosis Complex.

BACKGROUND: Individuals with tuberous sclerosis complex are at increased risk of epilepsy. Early seizure control improves developmental outcomes, making identifying at-risk patients critically important. Despite several identified risk factors, it remains difficult to predict. The purpose of the study was to evaluate the combined risk prediction of previously identified risk factors for epilepsy in individuals with tuberous sclerosis complex. METHODS: The study group (n = 333) consisted of individuals with tuberous sclerosis complex who were enrolled in the Tuberous Sclerosis Complex Autism Center of Excellence Research Network and UT TSC Biobank. The outcome was defined as having an epilepsy diagnosis. Potential risk factors included sex, TSC genotype, and tuber presence. Logistic regression was used to calculate the odds ratio and P value for the association between each variable and epilepsy. A clinical risk prediction model incorporating all risk factors was built. Area under the curve was calculated to characterize the full model's ability to discriminate individuals with tuberous sclerosis complex with and without epilepsy. RESULTS: The strongest risk for epilepsy was presence of tubers (95% confidence interval: 2.39 to 10.89). Individuals with pathogenic TSC2 variants were three times more likely (95% confidence interval: 1.55 to 6.36) to develop seizures compared with those with tuberous sclerosis complex from other causes. The combination of risk factors resulted in an area under the curve 0.73. CONCLUSIONS: Simple characteristics of patients with tuberous sclerosis complex can be combined to successfully predict epilepsy risk. A risk assessment model that incorporates sex, TSC genotype, protective TSC2 missense variant, and tuber presence correctly predicts epilepsy in 73% of patients with tuberous sclerosis complex.

The first reported case of Loeys-Dietz syndrome in a patient with biallelic SMAD3 variants.

Loeys-Dietz syndrome (LDS), a connective tissue disorder characterized by its vascular, skeletal, craniofacial, and cutaneous manifestations is caused by mutations in one of six genes (TGFBR1, TGFBR2, SMAD2, SMAD3, TGFB2, and TGFB3). Until recently, all reported cases of LDS have been attributed to heterozygous pathogenic variants in these genes. Here, we report the first case of Loeys-Dietz syndrome due to SMAD3 biallelic likely pathogenic variants in a 15-year-old male with classic Loeys-Dietz features, including dysmorphic facial features, significant scoliosis, and pectus excavatum, arachnodactyly, severe aortic root dilation, and diffuse arterial tortuosity. His parents are each heterozygous for the likely pathogenic variant and are more mildly affected. To our knowledge, this represents the first reported case of biallelic SMAD3-related Loeys-Dietz syndrome and the third case in the literature of biallelic LDS, indicating that there are multiple genetic modes of inheritance underlying this disorder.

De novo and inherited variants in ZNF292 underlie a neurodevelopmental disorder with features of autism spectrum disorder.

PURPOSE: Intellectual disability (ID) and autism spectrum disorder (ASD) are genetically heterogeneous neurodevelopmental disorders. We sought to delineate the clinical, molecular, and neuroimaging spectrum of a novel neurodevelopmental disorder caused by variants in the zinc finger protein 292 gene (ZNF292). METHODS: We ascertained a cohort of 28 families with ID due to putatively pathogenic ZNF292 variants that were identified via targeted and exome sequencing. Available data were analyzed to characterize the canonical phenotype and examine genotype-phenotype relationships. RESULTS: Probands presented with ID as well as a spectrum of neurodevelopmental features including ASD, among others. All ZNF292 variants were de novo, except in one family with dominant inheritance. ZNF292 encodes a highly conserved zinc finger protein that acts as a transcription factor and is highly expressed in the developing human brain supporting its critical role in neurodevelopment. CONCLUSION: De novo and dominantly inherited variants in ZNF292 are associated with a range of neurodevelopmental features including ID and ASD. The clinical spectrum is broad, and most individuals present with mild to moderate ID with or without other syndromic features. Our results suggest that variants in ZNF292 are likely a recurrent cause of a neurodevelopmental disorder manifesting as ID with or without ASD.

Tuberous Sclerosis Complex Genotypes and Developmental Phenotype.

BACKGROUND: Children with tuberous sclerosis complex (TSC), caused by pathogenic variants in TSC1/TSC2, are at risk for intellectual disability. TSC2 pathogenic variants appear to increase the risk, compared with TSC1. However, the effect of TSC2 pathogenic variants on early and specific domains of development hasn't been studied. Using an extensively phenotyped group, we aimed to characterize differences in early intellectual development between genotypes. METHODS: The study group (n = 92) included participants with TSC enrolled in a multicenter study involving genetic testing and detailed prospective phenotyping including the Mullen Scales of Early Learning, a validated measure of cognition, language, and motor development in babies and preschool children. Mean T-scores at 24 months for each Mullen Scales of Early Learning domain were calculated for children with, versus without, a TSC2 pathogenic variant. Multivariable linear regression models were used to compare the groups, adjusting for seizures. RESULTS: T-scores on every Mullen Scales of Early Learning domain were significantly worse in the TSC2 group. Below average composite scores were present in three-fourths of the TSC2 group, compared with one-fourth of those without TSC2. Having a TSC2 pathogenic variant was associated with lower composite Mullen Scales of Early Learning scores, even when corrected for seizures. CONCLUSIONS: In a well-characterized patient population with standardized assessment of multiple aspects of development, we found that having a TSC2 pathogenic variant was associated with significantly lower Mullen Scales of Early Learning scores at age 24 months, independent of seizures. These data suggest that a baby with a TSC2 pathogenic variant is at high risk for significant developmental delays by 24 months.

A De novo HDAC2 variant in a patient with features consistent with Cornelia de Lange syndrome phenotype.

Cornelia de Lange syndrome (CdLS) is an autosomal dominant genetic disorder caused by pathogenic variants in NIPBL, RAD21, SMC3, HDAC8, or SMC1A; all of which code for proteins that are components of, or interact with, the cohesin complex. Despite the identification of multiple genes associated with CdLS, over 25% of individuals strongly suspected to have CdLS have negative genetic testing, indicating that there are additional genes associated with the condition. HDAC2 codes for histone deacetylase 2 (HDAC2) and, like HDAC8, is a Class 1 histone deacetylase. We present a patient with a novel de novo variant in HDAC2 with many clinical features consistent with CdLS including severe developmental delay, limb abnormalities, congenital heart defect, cryptorchidism and hypoplastic genitalia, growth retardation, and characteristic craniofacial features. Although variants in HDAC2 are not currently associated with human disease, the variant identified in this patient is within a highly conserved amino acid residue and has not been observed in healthy populations. This information, along with the patient's clinical presentation and the functional similarity between the HDAC2 and HDAC8 proteins, suggests that HDAC2 should be further investigated as a candidate gene for CdLS or a CdLS-like syndrome.

Genetic Testing Practices of Genetic Counselors, Geneticists, and Pediatric Neurologists With Regard to Childhood-Onset Neurogenetic Conditions.

Identifying genetic diagnoses for neurologic conditions with a considerable hereditary component, such as autism spectrum disorder, intellectual disability, and epilepsy, is critical to providing proper medical management for patients and their families. However, many patients with these conditions are not tested appropriately or receive no genetic testing at all. The current study was designed to characterize the genetic testing practices of the providers most likely to evaluate or order genetic testing for these patients: pediatric neurologists, geneticists, and genetic counselors. Significant variance was present between testing strategies selected by pediatric neurologists and those by geneticists and genetic counselors, supporting the need for updated genetic testing guidelines that are consistent across specialties. Pediatric neurologists also report lower confidence in ordering genetic testing and desire further education regarding genetic testing. Together, these results propose that continued integration of genetics providers, such as genetic counselors, into pediatric neurology clinics may improve utilization of genetic testing while reducing the burden on pediatric neurologists.

The Impact of Psychiatric Symptoms on Tuberous Sclerosis Complex and Utilization of Mental Health Treatment.

BACKGROUND: Tuberous sclerosis complex (TSC) is a multisystem, neurocutaneous disorder with a spectrum of TSC-associated neuropsychiatric disorders. The most common neuropsychiatric manifestations in the pediatric and adult populations are cognitive concerns, depression, and anxiety. Previous research suggests that while 90% of individuals with TSC have some TSC-associated neuropsychiatric disorders features, only 20% receive treatment, leading to a 70% treatment gap. METHODS: This web-based study used validated measures in conjunction with researcher-designed questions to evaluate perception of disease severity, presence of anxiety and depression, and the utilization and barriers toward mental health services among adults with TSC. RESULTS: The Beck Anxiety Inventory, Beck Depression Inventory-II, and Brief Illness Perception Questionnaire indicated that our overall study population had mild symptoms of anxiety, minimal depression, and a moderate perception of disease severity. Notably, the difference between the median depression score for men and women was statistically significant with men scoring higher than women (P = 0.02). Of 69 respondents, 57% (n = 39) reported receiving mental health treatment at some point over their lifetime. In both the mental health treatment group and the nonmental health treatment group, cost was more often indicated as a barrier to accessing mental health resources (treatment group: cost = 51% and stigma = 21%; nontreatment group: cost = 27% and stigma = 20%). CONCLUSIONS: TSC disease severity had a moderate and low-moderate association with anxiety and depression, respectively. Regardless of past utilization, respondents had a positive outlook towards the use of mental health services with the major barrier being cost.

The expanding phenotype of RNU4ATAC pathogenic variants to Lowry Wood syndrome.

RNU4ATAC pathogenic variants to date have been associated with microcephalic osteodysplastic primordial dwarfism, type 1 and Roifman syndrome. Both conditions are clinically distinct skeletal dysplasias with microcephalic osteodysplastic primordial dwarfism, type 1 having a more severe phenotype than Roifman syndrome. Some of the overlapping features of the two conditions include developmental delay, microcephaly, and immune deficiency. The features also overlap with Lowry Wood syndrome, another rare but well-defined skeletal dysplasia for which the genetic etiology has not been identified. Characteristic features include multiple epiphyseal dysplasia and microcephaly. Here, we describe three patients with Lowry Wood syndrome with biallelic RNU4ATAC pathogenic variants. This report expands the phenotypic spectrum for biallelic RNU4ATAC disorder causing variants and is the first to establish the genetic cause for Lowry Wood syndrome.

TSC2 c.1864C>T variant associated with mild cases of tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is an autosomal dominantly inherited disorder with variable expressivity associated with hamartomatous tumors, abnormalities of the skin, and neurologic problems including seizures, intellectual disability, and autism. TSC is caused by pathogenic variants in either TSC1 or TSC2. In general, TSC2 pathogenic variants are associated with a more severe phenotype than TSC1 pathogenic variants. Here, we report a pathogenic TSC2 variant, c.1864C>T, p.(Arg622Trp), associated with a mild phenotype, with most carriers meeting fewer than two major clinical diagnostic criteria for TSC. This finding has significant implications for counseling patients regarding prognosis. More patient data are required before changing the surveillance recommendations for patients with the reported variant. However, consideration should be given to tailoring surveillance recommendations for all pathogenic TSC1 and TSC2 variants with documented milder clinical sequelae. © 2017 Wiley Periodicals, Inc.

Recurrent Muscle Weakness with Rhabdomyolysis, Metabolic Crises, and Cardiac Arrhythmia Due to Bi-allelic TANGO2 Mutations.

The underlying genetic etiology of rhabdomyolysis remains elusive in a significant fraction of individuals presenting with recurrent metabolic crises and muscle weakness. Using exome sequencing, we identified bi-allelic mutations in TANGO2 encoding transport and Golgi organization 2 homolog (Drosophila) in 12 subjects with episodic rhabdomyolysis, hypoglycemia, hyperammonemia, and susceptibility to life-threatening cardiac tachyarrhythmias. A recurrent homozygous c.460G>A (p.Gly154Arg) mutation was found in four unrelated individuals of Hispanic/Latino origin, and a homozygous ∼34 kb deletion affecting exons 3-9 was observed in two families of European ancestry. One individual of mixed Hispanic/European descent was found to be compound heterozygous for c.460G>A (p.Gly154Arg) and the deletion of exons 3-9. Additionally, a homozygous exons 4-6 deletion was identified in a consanguineous Middle Eastern Arab family. No homozygotes have been reported for these changes in control databases. Fibroblasts derived from a subject with the recurrent c.460G>A (p.Gly154Arg) mutation showed evidence of increased endoplasmic reticulum stress and a reduction in Golgi volume density in comparison to control. Our results show that the c.460G>A (p.Gly154Arg) mutation and the exons 3-9 heterozygous deletion in TANGO2 are recurrent pathogenic alleles present in the Latino/Hispanic and European populations, respectively, causing considerable morbidity in the homozygotes in these populations.

KIAA2022 nonsense mutation in a symptomatic female.

Mutations in the KIAA2022 gene have been implicated in non-syndromic X-linked intellectual disability. Thus far, all carrier females reported have been unaffected and genotype-phenotype correlations have not been described. Herein, we report a de novo KIAA2022 nonsense mutation in a 17-year-old female with short stature, microcephaly, severe intellectual disability, poor speech, epilepsy, and autistic behavior. X-inactivation pattern is normal suggesting that the mutation is causing the phenotype. This report contests the current view that KIAA2022 mutations only affect males, which has implications for testing and genetic counseling.

Therapeutic challenges in treating patients with fragile X syndrome and neoplasia.

The administration of cytotoxic therapy to patients with fragile X syndrome (FXS) presents several unique therapeutic challenges. The existence of fragile sites poses a theoretical risk of tumorigenesis and potentially increased treatment associated toxicity, however, controversy exists. We review the 42 previously reported cases of neoplasia in patients with FXS and report two novel neoplasms in patients treated with radiation therapy or combined chemoradiation. Our experience suggests that radiation therapy can be delivered safely in these patients without an expectation for increased acute/sub-acute normal tissue toxicity; however, treatment requires specialized facilities with the resources to deliver this care safely.