Human Genetics of Ventricular Septal Defect.

Ventricular septal defects (VSDs) are recognized as one of the commonest congenital heart diseases (CHD), accounting for up to 40% of all cardiac malformations, and occur as isolated CHDs as well as together with other cardiac and extracardiac congenital malformations in individual patients and families. The genetic etiology of VSD is complex and extraordinarily heterogeneous. Chromosomal abnormalities such as aneuploidy and structural variations as well as rare point mutations in various genes have been reported to be associated with this cardiac defect. This includes both well-defined syndromes with known genetic cause (e.g., DiGeorge syndrome and Holt-Oram syndrome) and so far undefined syndromic forms characterized by unspecific symptoms. Mutations in genes encoding cardiac transcription factors (e.g., NKX2-5 and GATA4) and signaling molecules (e.g., CFC1) have been most frequently found in VSD cases. Moreover, new high-resolution methods such as comparative genomic hybridization enabled the discovery of a high number of different copy number variations, leading to gain or loss of chromosomal regions often containing multiple genes, in patients with VSD. In this chapter, we will describe the broad genetic heterogeneity observed in VSD patients considering recent advances in this field.

Human Genetics of Hypoplastic Left Heart Syndrome.

Hypoplastic left heart syndrome (HLHS) is a severe congenital cardiovascular malformation characterized by hypoplasia of the left ventricle, aorta, and other structures on the left side of the heart. The pathologic definition includes atresia or stenosis of both the aortic and mitral valves. Despite considerable progress in clinical and surgical management of HLHS, mortality and morbidity remain concerns. One barrier to progress in HLHS management is poor understanding of its cause. Several lines of evidence point to genetic origins of HLHS. First, some HLHS cases have been associated with cytogenetic abnormalities (e.g., Turner syndrome). Second, studies of family clustering of HLHS and related cardiovascular malformations have determined HLHS is heritable. Third, genomic regions that encode genes influencing the inheritance of HLHS have been identified. Taken together, these diverse studies provide strong evidence for genetic origins of HLHS and related cardiac phenotypes. However, using simple Mendelian inheritance models, identification of single genetic variants that "cause" HLHS has remained elusive, and in most cases, the genetic cause remains unknown. These results suggest that HLHS inheritance is complex rather than simple. The implication of this conclusion is that researchers must move beyond the expectation that a single disease-causing variant can be found. Utilization of complex models to analyze high-throughput genetic data requires careful consideration of study design.

Epigenetics.

Epigenetics is the study of heritable changes to the genome and gene expression patterns that are not caused by direct changes to the DNA sequence. Examples of these changes include posttranslational modifications to DNA-bound histone proteins, DNA methylation, and remodeling of nuclear architecture. Collectively, epigenetic changes provide a layer of regulation that affects transcriptional activity of genes while leaving DNA sequences unaltered. Sequence variants or mutations affecting enzymes responsible for modifying or sensing epigenetic marks have been identified in patients with congenital heart disease (CHD), and small-molecule inhibitors of epigenetic complexes have shown promise as therapies for adult heart diseases. Additionally, transgenic mice harboring mutations or deletions of genes encoding epigenetic enzymes recapitulate aspects of human cardiac disease. Taken together, these findings suggest that the evolving field of epigenetics will inform our understanding of congenital and adult cardiac disease and offer new therapeutic opportunities.

Detection of 4p16.3 deletion and 11p15.5p15.4 gain in a boy by comparative genomic hybridization array: A case report.

BACKGROUND: Nonallelic homologous recombination (NAHR) of segmental duplications or low copy repeats (LCRs) result in DNA gain/loss and play an important role in the origin of genomic disorders. CASE SUMMARY: A 3-year- old boy was referred for genetic analysis. Comparative genomic hybridization array analysis revealed a loss of 3776 kb in the 4p16.3 chromosomal region and a gain of 3201 kb in the 11p15.5p15.4 chromosomal region. CONCLUSION: Genomic imbalances caused by NAHR in LCRs result in deletion and duplication syndromes.

Wolf-Hirschhorn syndrome candidate 1 (Whsc1) methyltransferase signals via a Pitx2-miR-23/24 axis to effect tooth development.

Wolf-Hirschhorn syndrome (WHS) is a developmental disorder attributed to a partial deletion on the short arm of chromosome 4. WHS patients suffer from oral manifestations including cleft lip and palate, hypodontia, and taurodontism. WHS candidate 1 (WHSC1) gene is a H3K36-specific methyltransferase that is deleted in every reported case of WHS. Mutation in this gene also results in tooth anomalies in patients. However, the correlation between genetic abnormalities and the tooth anomalies has remained controversial. In our study, we aimed to clarify the role of WHSC1 in tooth development. We profiled the Whsc1 expression pattern during mouse incisor and molar development by immunofluorescence staining and found Whsc1 expression is reduced as tooth development proceeds. Using real-time quantitative reverse transcription PCR, Western blot, chromatin immunoprecipitation, and luciferase assays, we determined that Whsc1 and Pitx2, the initial transcription factor involved in tooth development, positively and reciprocally regulate each other through their gene promoters. miRNAs are known to regulate gene expression posttranscriptionally during development. We previously reported miR-23a/b and miR-24-1/2 were highly expressed in the mature tooth germ. Interestingly, we demonstrate here that these two miRs directly target Whsc1 and repress its expression. Additionally, this miR cluster is also negatively regulated by Pitx2. We show the expression of these two miRs and Whsc1 are inversely correlated during mouse mandibular development. Taken together, our results provide new insights into the potential role of Whsc1 in regulating tooth development and a possible molecular mechanism underlying the dental defects in WHS.

Features of the Wolf-Hirschhorn Syndrome (WHS) from Infant to Young Teenager.

Wolf-Hirschhorn syndrome is a rare condition caused by terminal deletions, of variable size, in the short arm of chromosome 4. The syndrome displays the combination of typical morphological facial variations, intellectual disability, language delay, and various malformations. This report describes the clinical aspect and developmental evolution of a male patient with Wolf-Hirschhorn syndrome, from infancy to adolescence. The patient was first examined and diagnosed at 11 months, with follow-up at the ages of 4 and 16.

Genotype-phenotype correlation of deletions and duplications of 4p: case reports and literature review.

Structural rearrangements of chromosome 4p gives rise to a group of rare genomic disorders that mainly result in two different clinical entities: Wolf-Hirschhorn syndrome (WHS) and partial 4p trisomy. The severity of the phenotype depends on the size of the deletion or locus duplication. Here, we present two unrelated individuals with a copy number variation of chromosome 4p. Inverted duplication deletions (inv dup-del) in 4p are particularly rare. Case 1 describes a 15-year-old girl with a 1.055 Mb deletion of terminal 4p, distal to the recognized critical region of WHS, and a large duplication of 9.6 Mb in size from 4p16.3 to p16.1. She had postnatal development delay, intellectual disability (especially pronounced in speech), seizure/electroencephalogram anomalies, and facial dysmorphic features. This unusual chromosomal imbalance resulted in the WHS phenotype rather than the 4p trisomy syndrome phenotype. Case 2 describes a 21-month-old boy with a 1.386 Mb terminal 4p deletion who presented with slight developmental delay, borderline intellectual disability, and seizures. Combined with previous reported cases of 4 pter del-dup or pure 4p terminal deletions, our observations suggest that terminal chromosome 4p deletion is more pathogenic than the concomitant partial 4p duplication, and some regions of the 4p terminal may have regulatory effects on the remaining region of 4p. About nine cases have been reported thus far to date, and our study delineates further genotype-phenotype correlations about terminal 4p duplication-deletions for predicting disease prognosis and patient counseling.

Case report: A de novo NSD2 truncating variant in a child with Rauch-Steindl syndrome.

Wolf-Hirschhorn syndrome (WHS) is a rare genetic disorder caused by a heterozygous deletion on chromosome 4p16.3, which is called the WHS critical region (WHSC). The major features of this disorder, including "Greek warrior helmet" facies, delayed growth, intellectual disability, seizures, and skeletal abnormalities, are caused by the combined haploinsufficiency of multiple genes. The WHS candidate 1 (WHSC1) gene, also known as NSD2, is located in the WHSC and has been reported to associate with Rauch-Steindl syndrome (RSS,OMIM 619695). RSS is a highly heterogeneous disease characterized by mild developmental delay, prenatal-onset growth restriction, low body mass index, and characteristic facial features distinct from WHS. In this report, using whole exome sequencing (WES), we identified a novel de novo heterozygous NSD2 truncating variant in a 7-year-old Chinese girl with Rauch-Steindl syndrome, including failure to thrive, facial dysmorphisms, developmental delay, intellectual disability, and hypotonia. These findings further support that haploinsufficiency of NSD2 is necessary for WHS, and molecular genetic testing is more accurate to diagnose these patients. The novel variant uncovered in this study further expands the mutation spectrum of NSD2.

Prenatal phenotype of Wolf-Hirschhorn syndrome: A case series and literature review.

OBJECTIVE: Wolf-Hirschhorn syndrome (WHS) is a congenital malformation syndrome with poor prognosis. It is associated with a heterozygous deletion of chromosome 4p16.3. Adequate knowledge of prenatal phenotypes and proper prenatal counseling are essential for intrauterine diagnosis. METHOD: We retrospectively analyzed 11 prenatal cases of WHS diagnosed using low-depth whole-genome sequencing (copy number variation sequencing) performed at our hospital from May 2017 to September 2022 and reviewed their prenatal ultrasound reports in detail. We also analyzed WHS cases (including prenatal and postnatal) with abnormal prenatal ultrasound findings in the published literature over the past 20 years. RESULTS: Among the 11 fetuses with a prenatal diagnosis of WHS in our hospital, four cases showed abnormal prenatal ultrasound findings, including shrunken kidneys, ventricular septal defect, a small stomach, fetal growth restriction (FGR), enlarged posterior fossa, and soft ultrasonic markers. Our four cases were combined with 114 published WHS cases with prenatal ultrasound abnormalities from other medical institutions. Of the 118 cases, 59.3% (70 of 118) were multiple malformations. The most frequent ultrasound features observed in all 118 cases were FGR (76.3%, 90 of 118), followed by facial anomalies (28.8%, 34 of 118), central nervous system anomalies (27.1%, 32 of 118), and soft ultrasound markers (23.7%, 28 of 118). Other less common phenotypes included cardiac anomalies (19.5%, 23 of 118), genitourinary anomalies (19.5%, 23 of 118), increased NT/NF (12.7%, 15 of 118), skeletal anomalies (11.9%, 14 of 118), a single umbilical artery (10.2%, 12 of 118), gastrointestinal anomalies (9.3%, 11 of 118), oligohydramnios (8.5%, 10 of 118), cystic hygroma (5.1%, six of 118), hydrops/pleural effusion/ascites (2.5%, three of 118), and polyhydramnios (2.5%, three of 118). CONCLUSION: This study improved our understanding of the prenatal presentation of WHS by analyzing prenatal ultrasound abnormalities. The timely identification of prenatal ultrasound abnormalities can provide accurate consultation for pregnant women, improve the prenatal detection of WHS, and enable early prenatal management and intervention of WHS.

The constitutional gain-of-function variant p.Glu1099Lys in NSD2 is associated with a novel syndrome.

NSD2 dimethylates histone H3 at lysine 36 (H3K36me2) and is located in the Wolf-Hirschhorn syndrome (WHS) critical region. Recent descriptions have delineated loss-of-function (LoF) variants in NSD2 with a distinct disorder. The oncogenic missense variant p.Glu1099Lys occurs somatically in leukemia and has a gain-of-function (GoF) effect. We describe two individuals carrying p.Glu1099Lys as heterozygous de novo germline variant identified by exome sequencing (ES) of blood DNA and subsequently confirmed in two ectodermal tissues. Clinically, these individuals are characterized by intellectual disability, coarse/ square facial gestalt, abnormalities of the hands, and organomegaly. Public cell lines with NSD2 GoF variants had increased K36me2, DNA promoter methylation, and dysregulated RNA expression. NSD2 GoF caused by p.Glu1099Lys is associated with a novel phenotype different from WHS and Rauch-Steindl syndrome (RAUST).

Family report of Wolf-Hirschhorn syndrome in twins / 中华神经科杂志

Objective:To explore the clinical manifestations and genetic characteristics of Wolf-Hirschhorn syndrome (WHS) to improve the ability of diagnosis and differential diagnosis of the disease.Methods:The clinical features and auxiliary examinations and treatment of a proband with WHS caused by microdeletion of 4p16.3 segment who admitted to the Third Affiliated Hospital of Zhengzhou University in December 2021 were recorded, and whole exome sequencing (WES) of the family was performed. The prognosis was followed up.Results:The female proband, 11 months old, presented with convulsions at the age of 8 months, with the characteristics of heat sensitivity and cluster seizures, and her identical twin sister had a similar medical history. Physical examination found malnutrition, retarded development, special face, prominent forehead, wide nasal bridge, small jaw, precordial murmur and grade 3/6 murmur in the whole period, hyperactivity of P2, and low limb muscle tone. The whole exon and copy number variation (CNV) test of the family revealed that the proband had a 1.99 Mb heterozygous deletion in the chromosome 4p16.3 segment, including WHSC1 (NSD2), WHSC2 (NEFLA) and other genes. Copy number variation sequencing (CNV-Seq) of the proband and her sister showed 1.97 and 1.92 Mb heterozygous deletion of chromosome 4p16.3, respectively. Genealogical analysis by quantitative polymerase chain reaction revealed that the CNV was de novo, and it was determined to be a pathogenic variant according to the American College of Medical Genetics and Genomics guidelines. The proband took sodium valproate orally, and her sister took oral sodium valproate, zonisamide, and levetiracetam successively, and at the same time they received family rehabilitation training. The age at the last follow-up was 1 year and 8 months. Neither of them had convulsions again in the past 3 months, but the developmental delay was obvious. Conclusion:WHS patients may present with growth retardation, epilepsy, Greek warrior helmet-like special face, and congenital heart disease, and may have microdeletions in the chromosome 4p16.3 segment.

Wolf-Hirschhorn Syndrome with Hyperparathyroidism: A Case Report and a Narrative Review of the Literature.

Wolf-Hirschhorn syndrome (WHS) is a contiguous gene deletion condition. The WHS core phenotype includes developmental delays, intellectual disabilities, seizures, and distinctive facial features. Various other comorbidities have also been reported, such as hearing loss, heart defects, as well as eye problems and kidney problems. In this report, we present a case of WHS accompanied by hyperparathyroidism and hypercalcemia, which has not been previously reported. A girl was born at 37 weeks of gestation by vaginal delivery. She was small for the gestational age (2,045 g) and admitted to neonatal intensive care unit. She had typical WHS facial features and was found to have bilateral small kidneys associated with transient metabolic acidosis and renal insufficiency. She had right-sided sensorineural hearing loss, a small atrial septal defect, and colpocephaly and hypoplasia of corpus callosum. She had a single seizure which was well controlled with an oral antiepileptic medication. Cytogenetic studies demonstrated a large terminal chromosome 4p deletion (21.4 Mb) and 4p duplication (2.1 Mb) adjacent to the deletion. A unique finding in this patient is her consistently elevated levels of parathyroid hormone and serum calcium, suggesting hyperparathyroidism. We present this rare case along with a review of the literature and hope to draw an attention to a potential relationship between WHS and hyperparathyroidism.

Clinical and epilepsy characteristics in Wolf-Hirschhorn syndrome (4p-): A review.

Wolf-Hirschhorn syndrome (WHS) is araredisorderwithan estimated prevalence being around 1 in 50,000 births. The syndrome is caused by the deletion of a critical region (Wolf-Hirschhorn Syndrome Critical region- WHSCR) on chromosome 4p16.3. WHS is clinically characterized by pre-and postnatal growth restriction, hypotonia, intellectual disability, craniofacial dysmorphismand congenital fusion anomalies. The clinical aspects are variable due to the deletion size.Consistently, epilepsy is one of the major concerns for parents and professionals caring for children with WHS. Seizures tend to occur in over 90% of patients, with onset within the first 3 years of life, and a peak incidence at around 6-12 months of age. Approximately 20% of patients had the first seizure onset within the first 6 months of age, almost 50% at 6 to 12 months of age and about 25% later than 12 months of age. The main types of epileptic seizures occurring in patients with WHS were generalized tonic-clonic seizures (around 70%). These were followed by tonic spasms (20%); focal seizures with impaired awareness (12%) and clonicseizures in 7% of patients.Seizures are often triggered by fever, followed by infections of various systems. Particularly, half of WHS patients experience status epilepticus in the first years of life, which can be fatal. Due to limited number of reports on the topic of EEG abnormalities in epilepsy among WHS patients, it is difficult to determine whether there are any characteristic deviations for WHS. Although more than 300 persons with WHS have been reported in the literature, there is sparse knowledge about epilepsy and methods of its anti-seizure medication (ASM) management with an assessment of their effectiveness. The purpose of this systematic review is to briefly summarize achievements and advances in the field of epilepsy in Wolf-Hirschhorn syndrome.

Bi-allelic LETM1 variants perturb mitochondrial ion homeostasis leading to a clinical spectrum with predominant nervous system involvement.

Leucine zipper-EF-hand containing transmembrane protein 1 (LETM1) encodes an inner mitochondrial membrane protein with an osmoregulatory function controlling mitochondrial volume and ion homeostasis. The putative association of LETM1 with a human disease was initially suggested in Wolf-Hirschhorn syndrome, a disorder that results from de novo monoallelic deletion of chromosome 4p16.3, a region encompassing LETM1. Utilizing exome sequencing and international gene-matching efforts, we have identified 18 affected individuals from 11 unrelated families harboring ultra-rare bi-allelic missense and loss-of-function LETM1 variants and clinical presentations highly suggestive of mitochondrial disease. These manifested as a spectrum of predominantly infantile-onset (14/18, 78%) and variably progressive neurological, metabolic, and dysmorphic symptoms, plus multiple organ dysfunction associated with neurodegeneration. The common features included respiratory chain complex deficiencies (100%), global developmental delay (94%), optic atrophy (83%), sensorineural hearing loss (78%), and cerebellar ataxia (78%) followed by epilepsy (67%), spasticity (53%), and myopathy (50%). Other features included bilateral cataracts (42%), cardiomyopathy (36%), and diabetes (27%). To better understand the pathogenic mechanism of the identified LETM1 variants, we performed biochemical and morphological studies on mitochondrial K+/H+ exchange activity, proteins, and shape in proband-derived fibroblasts and muscles and in Saccharomyces cerevisiae, which is an important model organism for mitochondrial osmotic regulation. Our results demonstrate that bi-allelic LETM1 variants are associated with defective mitochondrial K+ efflux, swollen mitochondrial matrix structures, and loss of important mitochondrial oxidative phosphorylation protein components, thus highlighting the implication of perturbed mitochondrial osmoregulation caused by LETM1 variants in neurological and mitochondrial pathologies.

[Prevalence and geographic distribution of the Wolf-Hirschhorn syndrome in Spain.] / Prevalencia y distribución geográfica del síndrome de Wolf-Hirschhorn en España.

OBJECTIVE: Wolf-Hirschhorn syndrome is a rare disease of genetic origin caused by the deletion of the distal end of chromosome 4, including at least the region p16.3. The objectives of this work were to determine the prevalence of the disease in the Spanish population, as well as to establish the geographical distribution of the syndrome throughout the Spanish geography, elucidating the age range in which there are more patients. METHODS: Patients diagnosed with the disease for nine years (2013-2021) throughout the Spanish territory were recruited for the research, thanks to agreements with the Spanish Association of Wolf-Hirschhorn Syndrome (AESWH). The clinical information of the patients was obtained from referring physicians using two standardized questionnaires completed with data from medical reports and the parent interview. The molecular characterization of the disease was made using SNP (single nucleotide polymorphism) microarrays (cytoSNP850K, Illumina, USA). The data were statistically processed using Microsoft Excel (Microsoft Corporation) and SPSS (IBM) software, using comparisons between two groups s with Student's t-test (for continuous variables) or with Chi-square tests (for categorical ones). For more than two groups, ANOVA analyses were performed (followed by Bonferroni or T3-Dunnett post hoc tests) for continuous variables and z-tests between column proportions for categorical variables. RESULTS: In Spain (until 2021) eighty people are diagnosed with this syndrome, estimating its prevalence at 1.69x10-4 per 10,000 inhabitants and / or 1/172,904 for each live newborn. This paper remarks the existence of important differences in prevalence between the different regions in Spain. The region with the most diagnosed patients was Madrid, although the highest prevalence was observed in Asturias. Significant differences have been established in terms of sex and disease (ratio of women to men of 2:1), and the mean age at diagnosis has been established at 7.20 years. CONCLUSIONS: The prevalence of this syndrome in Spain has been estimated well below the prevalence that is handled in scientific texts (1/50,000 newborns). In addition, we have determined that this prevalence shows large geographical differences, which allows us to affirm that this syndrome could be under-diagnosed in our country. Most of the patients included in this cohort are of paediatric age. It has not been possible to corroborate that mortality in this syndrome, in our population, occurs preferably during the first two years of life, as has been claimed.

OBJETIVO: El Síndrome de Wolf-Hirschhorn es una enfermedad poco frecuente de origen genético causada por la deleción del extremo distal del cromosoma 4, que incluye preferentemente la región p16.3. Los objetivos de este trabajo fueron determinar la prevalencia de la enfermedad en la población española, así como establecer la distribución geográfica del síndrome a lo largo de la geografía nacional, dilucidando el rango de edad en el que existían más pacientes afectados. METODOS: Para la investigación se reclutaron 80 pacientes diagnosticados con el síndrome en el periodo 2013-2021, en todo el territorio español, gracias a los acuerdos con la Asociación Española de Síndrome Wolf-Hirschhorn (AESWH). La información clínica de los pacientes se obtuvo mediante dos cuestionarios estandarizados que fueron cumplimentados por médicos de referencia y los padres, siendo completados y corroborados con los distintos informes médicos de cada paciente y, al menos, una entrevista una entrevista a los padres. La caracterización molecular de la enfermedad se realizó mediante el uso de microarrays de SNP (del inglés, single nucleotide polymorphism) (CytoSNP 850K, Illumina). Los datos se trataron estadísiticamente utilizando los softwares Microsoft Excel (Microsoft Corporation) y SPSS (IBM), mediante las comparaciones entre dos grupos s con la prueba t de Student (para variables continuas) o con pruebas de Chi cuadrado (para las categóricas). Para más de dos grupos se realizó análisis ANOVA (seguido de las pruebas post hoc de Bonferroni o T3-Dunnett) para variables continuas y pruebas z entre proporciones de columna para variables categóricas. RESULTADOS: En España (hasta 2021) están diagnosticadas ochenta personas con este síndrome, estimándose su prevalencia en 1,69x10-4 por cada 10.000 habitantes y/o 1/172.904 por cada recién nacido vivo. En este trabajo se constató la existencia de importantes diferencias de prevalencia entre las comunidades autónomas de nuestro país. La comunidad con más pacientes diagnosticados fue Madrid, aunque la mayor prevalencia se observó en Asturias. Se establecieron diferencias estadísticamente significativas en cuanto al sexo y la enfermedad (proporción de mujeres sobre varones de 2:1), así como se estableció la edad media al diagnóstico en 7,20 años. CONCLUSIONES: La prevalencia de este síndrome en España se estima muy por debajo de la prevalencia que se maneja en los textos científicos (1 por cada 50.000 recién nacidos). Adicionalmente, hemos determinado que esta prevalencia muestra grandes diferencias geográficas, lo que nos permite afirmar que este síndrome podría encontrarse infra-diagnosticado en nuestro país. La mayor parte de los pacientes incluidos en esta cohorte se encuentran en edad pediátrica. No se ha podido corroborar que la mortalidad en este síndrome, en nuestra población, ocurra preferentemente durante los dos primeros años de vida, como se venía afirmando.

Prevalencia y distribución geográficadel síndrome de Wolf-Hirschhornen España / Prevalence and geographic distribution of the Wolf-Hirschhorn syndrome in Spain

FUNDAMENTOS: El Síndrome de Wolf-Hirschhorn es una enfermedad poco frecuente de origen genético causada por la delecióndel extremo distal del cromosoma 4, que incluye preferentemente la región p16.3. Los objetivos de este trabajo fueron determinar laprevalencia de la enfermedad en la población española, así como establecer la distribución geográfica del síndrome a lo largo de lageografía nacional, dilucidando el rango de edad en el que existían más pacientes afectados.MÉTODOS: Para la investigación se reclutaron 80 pacientes diagnosticados con el síndrome en el periodo 2013-2021, en todo elterritorio español, gracias a los acuerdos con la Asociación Española de Síndrome Wolf-Hirschhorn (AESWH). La información clínica de los pacientes se obtuvo mediante dos cuestionarios estandarizados que fueron cumplimentados por médicos de referencia y los padres, siendo completados y corroborados con los distintos informes médicos de cada paciente y, al menos, una entrevista una entrevista a los padres. La caracterización molecular de la enfermedad se realizó mediante el uso de microarrays de SNP(del inglés, single nucleotide polymorphism) (CytoSNP 850K, Illumina). Los datos se trataron estadísiticamente utilizando los softwaresMicrosoft Excel (Microsoft Corporation) y SPSS (IBM), mediante las comparaciones entre dos grupos s con la prueba t de Student (para variables continuas) o con pruebas de Chi cuadrado (para las categóricas). Para más de dos grupos se realizó análisis ANOVA (seguido de las pruebas post hoc de Bonferroni o T3-Dunnett) para variables continuas y pruebas z entre proporciones de columna para variables categóricas. RESULTADOS: En España (hasta 2021) están diagnosticadas ochenta personas con este síndrome, estimándose su prevalencia en1,69x10-4 por cada 10.000 habitantes y/o 1/172.904 por cada recién nacido vivo. En este trabajo se constató la existencia de importantesdiferencias de prevalencia entre las comunidades autónomas de nuestro país.(AU)

BACKGROUND: Wolf-Hirschhorn syndrome is a rare disease of genetic origin caused by the deletion of the distal end of chromo-some 4, including at least the region p16.3. The objectives of this work were to determine the prevalence of the disease in the Spanishpopulation, as well as to establish the geographical distribution of the syndrome throughout the Spanish geography, elucidating theage range in which there are more patients. METHODS: Patients diagnosed with the disease for nine years (2013-2021) throughout the Spanish territory were recruited for theresearch, thanks to agreements with the Spanish Association of Wolf-Hirschhorn Syndrome (AESWH). The clinical information of thepatients was obtained from referring physicians using two standardized questionnaires completed with data from medical reports andthe parent interview. The molecular characterization of the disease was made using SNP (single nucleotide polymorphism) microarrays (cytoSNP850K, Illumina, USA). The data were statistically processed using Microsoft Excel (Microsoft Corporation) and SPSS (IBM) software,using comparisons between two groups s with Student’s t-test (for continuous variables) or with Chi-square tests (for categorical ones).For more than two groups, ANOVA analyses were performed (followed by Bonferroni or T3-Dunnett post hoc tests) for continuous varia-bles and z-tests between column proportions for categorical variables. RESULTS: In Spain (until 2021) eighty people are diagnosed with this syndrome, estimating its prevalence at 1.69x10-4 per 10,000inhabitants and / or 1/172,904 for each live newborn. This paper remarks the existence of important differences in prevalence betweenthe different regions in Spain. The region with the most diagnosed patients was Madrid, although the highest prevalence was obser-ved in Asturias.(AU)

From Wolf-Hirschhorn syndrome to NSD2 haploinsufficiency: a shifting paradigm through the description of a new case and a review of the literature.

BACKGROUND: Wolf-Hirschhorn syndrome (WHS) is a well-defined disorder, whose core phenotype encompasses growth restriction, facial gestalt, intellectual disability and seizures. Nevertheless, great phenotypic variability exists due to the variable extent of the responsible 4p deletion. In addition, exome sequencing analyses, recently identified two genes, namely NSD2 and NELFA, whose loss-of-function variants contribute to a clinical spectrum consistent with atypical or partial WHS. The observation of patients exhibiting clinical features resembling WHS, with only mild developmental delay and without the typical dysmorphic features, carrying microdeletions sparing NSD2, has lead to the hypothesis that NSD2 is responsible for the intellectual disability and the facial gestalt of WHS. While presenting some of the typical findings of WHS (intellectual disability, facial gestalt, microcephaly, growth restriction and congenital heart defects), NSD2-deleted children tend to display a milder spectrum of skeletal abnormalities, usually consisting of clinodactyly, and do not exhibit seizures. We describe the clinical picture of a child with WHS due to a de novo mutation of NSD2 and discuss the clinical and diagnostic implications. CASE PRESENTATION: A 6-year-old boy was evaluated for a history of intrauterine growth restriction, low birth weight, neonatal hypotonia, and psychomotor delay. No episodes of seizure were reported. At physical examination, he displayed marphanoid habitus, muscle hypotrophy and facial dysmorphisms consisting in high frontal hairline, upslanting palpebral fissures and full lips with bifid ugula. Cryptorchidism, shawl scrotum, mild clinodactyly of the right little finger and bilateral syndactyly of the II and III toes with sandal gap were also noted. The radiographic essay demonstrated delayed bone age and echocardiography showed mild mitral prolapse. Whole genome sequencing analysis revealed a heterozygous de novo variant of NSD2 (c.2523delG). CONCLUSIONS: Full WHS phenotype likely arises from the cumulative effect of the combined haploinsufficiency of several causative genes mapping within the 4p16.3 region, as a contiguous genes syndrome, with slightly different phenotypes depending on the specific genes involved in the deletion. When evaluating children with pictures resembling WHS, in absence of seizures, clinicians should consider this differential diagnosis.

Prenatal sonographic findings in confirmed cases of Wolf-Hirschhorn syndrome.

BACKGROUND: Wolf-Hirschhorn syndrome (WHS) is a common genetic condition and prenatal diagnosis is difficult due to heterogeneous expression of this syndrome and rather non-specific ultrasound findings. Objective of this study was to examine the prenatal ultrasound findings in fetuses with Wolf-Hirschhorn syndrome (WHS). METHODS: Retrospective assessment of 18 pregnancies that were seen at three tertiary referral centers (Universities of Bonn, Tuebingen and Nuernberg / Germany). Findings of prenatal ultrasound examinations, genetic results and outcome were compared. Additionally, findings of our study were compared to previous small case series from the literature and then compared to data on postnatal frequencies and abnormalities in affected patients. RESULTS: Median gestational age at the time of examination was 23 + 1 weeks' (range: 13 + 4 to 29 + 1 weeks') with female-to-male ratio of > 2.5:1. Most frequent ultrasound findings were facial abnormalities, symmetric IUGR and microcephaly that presented in 94.4, 83.3 and 72.2% of cases, respectively. The combination of microcephaly and hypoplastic nasal bone was a particularly characteristic finding. Growth retardation presented in all fetuses > 20 weeks, but not below. Other frequent abnormalities included cardiac anomalies in 50 and single umbilical artery (SUA) in 44.4% of fetuses. CONCLUSION: WHS should be considered in the presence of symmetric IUGR together with microcephaly, hypoplastic nasal bone and facial abnormalities on prenatal ultrasound. Genetic testing by chromosomal microarray analysis (CMA) is strongly recommended in this context.

Distinct Epileptogenic Mechanisms Associated with Seizures in Wolf-Hirschhorn Syndrome.

Seizures are one of the clinical hallmarks of Wolf-Hirschhorn syndrome (WHS), causing a significant impact on the life quality, still in the first years of life. Even that the knowledge about WHS-related seizure candidate genes has grown, cumulative evidence suggests synergic haploinsufficiency of distinct genes within cellular networks that should be better elucidated. Herein, we evaluated common mechanisms between candidate genes from WHS seizure-susceptibility regions (SSR) and genes globally associated with epilepsy. For this purpose, data from 94 WHS patients delineated by chromosomal microarray analysis were integrated into a tissue-specific gene network with gene expression, drugs, and biological processes. We found functional modules and signaling pathways involving candidate and new genes with potential involvement in the WHS-related seizure phenotype. The proximity among the previous reported haploinsufficient candidate genes (PIGG, CPLX1, CTBP1, LETM1) and disease genes associated with epilepsy suggests not just one, but different impaired mechanisms in cellular networks responsible for the balance of neuronal activity in WHS patients, from which neuron communication is the most impaired in WHS-related seizures. Furthermore, CTBP1 obtained the largest number of drug associations, reinforcing its importance for adaptations of brain circuits and its putative use as a pharmacological target for treating seizures/epilepsy in patients with WHS.

A practical approach to dental care for patients with Wolf-Hirschhorn syndrome.

Wolf-Hirschhorn syndrome is a polymalformative chromosomal disorder caused by a deletion in the distal region of the short arm of chromosome 4. The disease is considered rare (1/50,000 births) and predominantly affects females (2:1). In addition to the characteristic facial phenotype ("Greek warrior helmet"), its clinical manifestations include epilepsy, developmental and psychomotor delay, intellectual disability, cardiac and respiratory complications, and eating problems. The most prevalent oral manifestations are hypodontia, delayed tooth eruption, morphological dental abnormalities, dental malocclusions, cleft lip/palate and ogival palate. Based on our clinical experience, Wolf-Hirschhorn syndrome does not represent an absolute contraindication for any type of dental procedure. The feasibility of dental treatment will depend mainly on the degree of epilepsy control and on the level of collaboration, this latter conditioned by the severity of the intellectual disability and communication difficulties.