TELO2-related syndrome (You-Hoover-Fong syndrome): Description of 14 new affected individuals and review of the literature

You-Hoover-Fong syndrome (YHFS) is an autosomal recessive condition caused by pathogenic variants in the TELO2 gene. Affected individuals were reported to have global developmental delay, intellectual disability, microcephaly, dysmorphic facial features, ocular involvement including cortical visual impairment, strabismus, cataract and rotatory nystagmus, movement disorder, hypertonia and spasticity, balance disturbance and ataxia, and abnormal sleep pattern. Other features reported include poor growth, cleft palate, cardiac malformations, epilepsy, scoliosis, and hearing loss. To date, 12 individuals with YHFS have been reported in the literature. Here we describe 14 new individuals with YHFS from 10 families. Their clinical presentation provides additional support of the phenotype recognized previously and delineates the clinical spectrum associated with YHFS syndrome. In addition, we present a review of the literature including follow-up data on four previously reported individuals with YHFS.     

Genotype–phenotype specificity in Menke–Hennekam syndrome caused by missense variants in exon 30 or 31 of CREBBP

CREBBP loss‐of function variants cause Rubinstein–Taybi syndrome (RTS). There have been two separate reports of patients with missense variants in exon 30 or 31 of CREBBP in individuals lacking the characteristic facial and limb dysmorphism associated with RTS. Frequent features in this condition include variable intellectual disability, short stature, autistic behavior, microcephaly, feeding problems, epilepsy, recurrent upper airway infections, and mild hearing impairment. We report three further patients with de novo exon 31 CREBBP missense variants. The first individual has a c.5357G>A p. (Arg1786His) variant affecting the same codon as one of the previously described patients. Both these patients could be recognized by clinicians as mild RTS. Our second patient has a c.5602C>T p.(Arg1868Trp) variant that has been described in five other individuals who all share a strikingly similar phenotype. The third individual has a novel c.5354G>A p.(Cys1785Try) variant. Our reports expand the clinical spectrum to include ventriculomegaly, absent corpus callosum, staphyloma, cochlear malformations, and exomphalos. These additional cases also help to establish genotype–phenotype correlations in this disorder. After the first and last authors of the previous two reports, we propose to call this disorder “Menke–Hennekam syndrome” to establish it as a clinical entity distinct from RTS and to provide a satisfactory name for adoption by parents and professionals, thus facilitating appropriate clinical management and research.     

Neurological phenotype of Potocki–Lupski syndrome

Potocki–Lupski syndrome is a condition mainly characterized by infantile hypotonia, developmental delay/intellectual disability (DD/ID), and congenital anomalies, caused by duplications of the 17p11.2 region, encompassing RAI1 gene. Its clinical presentation is extremely variable, especially for what concerns the cognitive level and the behavioral phenotype. Such aspects, as well as the dysmorphic/malformative ones, have been covered by previous studies; otherwise neurological features have never been systematically described. In order to delineate the neurological phenotype of Potocki–Lupski Syndrome, we collect an 8‐patients cohort. Developmental milestones are delayed and a mild to moderate cognitive impairment is present in all patients, variably associated with features of autism spectrum disorder, behavioral disturb, and sleep disturb. Hypotonia appears a less frequent finding than what previously reported, while motor clumsiness/coordination impairment is frequent. EGG registration demonstrated a common pattern with excess of diffuse rhythmic activity in sleep phases or while the patient is falling asleep. Brain MRI did not reveal common anomalies, although unspecific white matter changes may be present. We discuss such findings and compare them to literature data, offering an overview on the neurological and cognitive‐behavioral presentation of the syndrome.     

Expanding the phenotypic spectrum consequent upon de novo WDR37 missense variants

Structural eye disorders are increasingly recognised as having a genetic basis, although current genetic testing is limited in its success. De novo missense variants in WDR37 are a recently described cause of a multisystemic syndromic disorder featuring ocular coloboma. This study characterises the phenotypic spectrum of this disorder and reports 2 de novo heterozygous variants (p.Thr115Ile, p.Ser119Tyr) in three unrelated Caucasian individuals. All had a clinical phenotype consisting of bilateral iris and retinal coloboma, developmental delay and additional, variable multisystem features. The variants fall within a highly conserved region upstream of the WD-repeat domains, within an apparent mutation cluster. Consistent with the literature, intellectual disability, structural eye disorders, epilepsy, congenital heart disease, genitorenal anomalies and dysmorphic facial features were observed. In addition, a broader developmental profile is reported with a more specific musculoskeletal phenotype described in association with the novel variant (p.Thr115Ile). We further expand the phenotypic spectrum of WDR37-related disorders to include those with milder developmental delay and strengthen the association of ocular coloboma and musculoskeletal features. We promote the inclusion of WDR37 on gene panels for intellectual disability, epilepsy and structural eye disorders.     

BAZ2B haploinsufficiency as a cause of developmental delay,intellectual disability,and autism spectrum disorder

The bromodomain adjacent to zinc finger 2B gene (BAZ2B) encodes a protein involved in chromatin remodeling. Loss of BAZ2B function has been postulated to cause neurodevelopmental disorders. To determine whether BAZ2B deficiency is likely to contribute to the pathogenesis of these disorders, we performed bioinformatics analyses that demonstrated a high level of functional convergence during fetal cortical development between BAZ2B and genes known to cause autism spectrum disorder (ASD) and neurodevelopmental disorder. We also found an excess of de novo BAZ2B loss‐of‐function variants in exome sequencing data from previously published cohorts of individuals with neurodevelopmental disorders. We subsequently identified seven additional individuals with heterozygous deletions, stop‐gain, or de novo missense variants affecting BAZ2B. All of these individuals have developmental delay (DD), intellectual disability (ID), and/or ASD. Taken together, our findings suggest that haploinsufficiency of BAZ2B causes a neurodevelopmental disorder, whose cardinal features include DD, ID, and ASD.     

Variants in GNAI1 cause a syndrome associated with variable features including developmental delay,seizures, and hypotonia

PurposeNeurodevelopmental disorders (NDDs) encompass a spectrum of genetically heterogeneous disorders with features that commonly include developmental delay, intellectual disability, and autism spectrum disorders. We sought to delineate the molecular and phenotypic spectrum of a novel neurodevelopmental disorder caused by variants in the GNAI1 gene.MethodsThrough large cohort trio-based exome sequencing and international data-sharing, we identified 24 unrelated individuals with NDD phenotypes and a variant in GNAI1, which encodes the inhibitory Gαi1 subunit of heterotrimeric G-proteins. We collected detailed genotype and phenotype information for each affected individual.ResultsWe identified 16 unique variants in GNAI1 in 24 affected individuals; 23 occurred de novo and 1 was inherited from a mosaic parent. Most affected individuals have a severe neurodevelopmental disorder. Core features include global developmental delay, intellectual disability, hypotonia, and epilepsy.ConclusionThis collaboration establishes GNAI1 variants as a cause of NDDs. GNAI1-related NDD is most often characterized by severe to profound delays, hypotonia, epilepsy that ranges from self-limiting to intractable, behavior problems, and variable mild dysmorphic features.     

Novel dominant-negative NR2F1 frameshift mutation and a phenotypic expansion of the Bosch-Boonstra-Schaaf optic atrophy syndrome

Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) has been described as an autosomal-dominant disorder caused by mutations in the NR2F1 gene, whose common characteristics include developmental delay, intellectual disability, optic nerve atrophy, hypotonia, attention deficit disorder, autism spectrum disorder, seizures, hearing defects, spasticity and thinning of the corpus callosum. Missense mutations in NR2F1 have been reported to be the major cause of BBSOAS. A possible genotype-phenotype correlation has been considered with missense mutations affecting the ligand-binding domain of NR2F1 as well as whole-gene deletions of NR2F1 showing a milder phenotype of BBSOAS. Here we report on a patient with a novel frameshift mutation in NR2F1 showing the full spectrum of BBOAS indicating an expanded clinical spectrum and a reconsideration of the observed genotype-phenotype correlation.     

A novel patient with White–Sutton syndrome refines the mutational and clinical repertoire of the POGZ‐related phenotype and suggests further observations

A rare developmental delay (DD)/intellectual disability (ID) syndrome with craniofacial dysmorphisms and autistic features, termed White–Sutton syndrome (WHSUS, MIM#614787), has been recently described, identifying truncating mutations in the chromatin regulator POGZ (KIAA0461, MIM#614787). We describe a further WHSUS patient harboring a novel nonsense de novo POGZ variant, which afflicts a protein domain with transposase activity less frequently impacted by mutational events (DDE domain). This patient displays additional physical and behavioral features, these latter mimicking Smith–Magenis syndrome (SMS, MIM#182290). Considering sleep–wake cycle anomalies and abnormal behavior manifested by this boy, we reinforced the clinical resemblance between WHSUS and SMS, being both chromatinopathies. In addition, using the DeepGestalt technology, we identified a different facial overlap between WHSUS patients with mutations in the DDE domain (Group 1) and individuals harboring variants in other protein domains/regions (Group 2). This report further delineates the clinical and molecular repertoire of the POGZ‐related phenotype, adding a novel patient with uncommon clinical and behavioral features and provides the first computer‐aided facial study of WHSUS patients.     

Cognitive,adaptive and behavioral profile in Sotos syndrome children with 5q35 microdeletion or intragenic variants

Sotos syndrome (SoS) is a congenital overgrowth syndrome with variable degree of intellectual disability caused in the 90% of cases by pathogenetic variants of the Nuclear receptor binding SET Domain protein1 (NSD1) gene. NSD1 gene functions can be abrogated by different genetic alterations (i.e., small intragenic pathogenic variants like deletions/insertions, nonsense/missense pathogenic variants, partial gene deletions and whole deletions or microdeletion of 5q35 chromosomal region). Therefore, correlation of the genotype–phenotype with a possible contribution of more implicated genes to the medical, cognitive and behavioral profile is a topic of great interest. Although a more severe learning disability has been described in individuals with 5q35 microdeletion when compared to individuals with NSD1 intragenic pathogenic variants a fully delineated cognitive and behavioral phenotype has not been described yet. The importance of providing clinical characterization in relation to the genotype comes from the necessity to early identify children more at risk of developing psychopathological disorders. We characterize the cognitive, adaptive and behavioral phenotype of a pediatric sample of 64 individuals affected by SoS, performing a standardized neuropsychological evaluation. Secondly, we compare cognitive-behavioral profiles of SoS individuals carrying and not carrying the 5q35 microdeletion. SoS participants were characterized by a mild cognitive impairment of both Intellectual Quotient and adaptive skills in association to borderline symptoms of attention deficit. Our results suggest that the 5q35 microdeletion is associated with lower scores specifically concerning the cognitive, adaptive functioning and behavioral domains. However, longitudinal studies are necessary to confirm these findings and delineate a developmental trajectory of SoS.     

Expanding the phenotypic spectrum of MBOAT7‐related intellectual disability

MBOAT7 gene pathogenic variants are a newly discovered and rare cause for intellectual disability, autism spectrum disorder (ASD), seizures, truncal hypotonia, appendicular hypertonia, and below average head sizes (ranging from ?1 to ?3 standard deviations). There have been only 16 individuals previously reported who have MBOAT7‐related intellectual disability, all of whom were younger than 10 years old and from consanguineous relationships. Thus, there is a lack of phenotypic information for adolescent and adult individuals with this disorder. Medical genetics and psychiatric evaluations in a 14‐year‐old female patient with a history of global developmental delay, intellectual disability, overgrowth with macrocephaly, metrorrhagia, seizures, basal ganglia hyperintensities, nystagmus, strabismus with amblyopia, ASD, anxiety, attention deficit hyperactivity disorder (ADHD), aggressive outbursts, and hyperphagia included a karyotype, methylation polymerase chain reaction for Prader‐Willi/Angelman syndrome, chromosome microarray, and whole exome sequencing (WES), ADOS2, and ADI‐R. WES identified a homozygous, likely pathogenic variant in the MBOAT7 gene (c.855‐2A>G). This is the oldest known patient with MBOAT7‐related intellectual disability, whose unique features compared with previously described individuals include overgrowth with macrocephaly, metrorrhagia, ophthalmological abnormalities, basal ganglia hyperintensities, unspecified anxiety disorder, and ADHD; combined type; and hyperphagia with the absence of appendicular hypertonia and cortical atrophy. More individuals need to be identified in order to delineate the full clinical spectrum of this disorder.     

Phenotypic expansion of POGZ‐related intellectual disability syndrome (White‐Sutton syndrome)

White‐Sutton syndrome (WHSUS) is a recently‐identified genetic disorder resulting from de novo heterozygous pathogenic variants in POGZ. Thus far, over 50 individuals have been reported worldwide, however phenotypic characterization and data regarding the natural history are still incomplete. Here we report the clinical features of 22 individuals with 21 unique loss of function POGZ variants. We observed a broad spectrum of intellectual disability and/or developmental delay with or without autism, and speech delay in all individuals. Other common problems included ocular abnormalities, hearing loss and gait abnormalities. A validated sleep disordered breathing questionnaire identified symptoms of obstructive sleep apnea in 4/12 (33%) individuals. A higher‐than‐expected proportion of cases also had gastrointestinal phenotypes, both functional and anatomical, as well as genitourinary anomalies. In line with previous publications, we observed an increased body mass index (BMI) z‐score compared to the general population (mean 0.59, median 0.9; p 0.0253). Common facial features included microcephaly, broad forehead, midface hypoplasia, triangular mouth, broad nasal root and flat nasal bridge. Analysis of the Baylor Genetics clinical laboratory database revealed that POGZ variants were implicated in approximately 0.14% of cases who underwent clinical exome sequencing for neurological indications with or without involvement of other body systems. This study describes a greater allelic series and expands the phenotypic spectrum of this new syndromic form of intellectual disability and autism.     

De novo variants in KLF7 are a potential novel cause of developmental delay/intellectual disability,neuromuscular and psychiatric symptoms

Due to small numbers of reported patients with pathogenic variants in single genes, the phenotypic spectrum associated with genes causing neurodevelopmental disorders such as intellectual disability (ID) and autism spectrum disorder is expanding. Among these genes is KLF7 (Krüppel‐like factor 7), which is located at 2q33.3 and has been implicated in several developmental processes. KLF7 has been proposed to be a candidate gene for the phenotype of autism features seen in patients with a 2q33.3q34 deletion. Herein, we report 4 unrelated individuals with de novo KLF7 missense variants who share similar clinical features of developmental delay/ID, hypotonia, feeding/swallowing issues, psychiatric features and neuromuscular symptoms, and add to the knowledge about the phenotypic spectrum associated with KLF7 haploinsufficiency.     

The CHD4-related syndrome: a comprehensive investigation of the clinical spectrum,genotype–phenotype correlations,and molecular basis

PurposeSifrim–Hitz–Weiss syndrome (SIHIWES) is a recently described multisystemic neurodevelopmental disorder caused by de novo variants inCHD4. In this study, we investigated the clinical spectrum of the disorder, genotype–phenotype correlations, and the effect of different missense variants on CHD4 function.MethodsWe collected clinical and molecular data from 32 individuals with mostly de novo variants in CHD4, identified through next-generation sequencing. We performed adenosine triphosphate (ATP) hydrolysis and nucleosome remodeling assays on variants from five different CHD4 domains.ResultsThe majority of participants had global developmental delay, mild to moderate intellectual disability, brain anomalies, congenital heart defects, and dysmorphic features. Macrocephaly was a frequent but not universal finding. Additional common abnormalities included hypogonadism in males, skeletal and limb anomalies, hearing impairment, and ophthalmic abnormalities. The majority of variants were nontruncating and affected the SNF2-like region of the protein. We did not identify genotype–phenotype correlations based on the type or location of variants. Alterations in ATP hydrolysis and chromatin remodeling activities were observed in variants from different domains.ConclusionThe CHD4-related syndrome is a multisystemic neurodevelopmental disorder. Missense substitutions in different protein domains alter CHD4 function in a variant-specific manner, but result in a similar phenotype in humans.     

The progression of Wiedemann–Steiner syndrome in adulthood and two novel variants in the KMT2A gene

Wiedemann–Steiner syndrome is a genetic condition associated with dysmorphic facies, hypertrichosis, short stature, developmental delay, and intellectual disability. Congenital malformations of the cerebral, cardiac, renal, and optic structures have also been reported. Because the majority of reported individuals with this condition have been under age 20, the long‐term prognosis is not well defined. Here we report on two further unrelated individuals diagnosed with Wiedemann–Steiner syndrome, one of whom is in her third decade of life. In addition, both individuals have novel KMT2A mutations. The information provided below about the outcome in Wiedemann–Steiner syndrome is important for families of affected individuals.