22q13.33 duplication involving SHANK3 gene: a boy and his mother with "persistent" language and speech sound disorder.

Patients carrying 22q13.33 duplication present variable neurodevelopmental phenotype. Among these, patients with genetic alteration disrupting SHANK3 gene are very rare and they also present neurodevelopmental disorder such as autism spectrum disorder and intellectual disability. The real incidence is unknown because mild and variable phenotype could cause reduction in diagnosed cases. We describe the first case of 22q13.33 microduplication disrupting SHANK3 gene, inherited from mother to son, that presents a "persistent" language and speech sound disorder as main symptom without intellectual disability and autism spectrum disorder. More clinical reports with accurate phenotype description are needed to better define the profile of carriers of this genetic alteration.

Snijders Blok-Campeau Syndrome: Description of 20 Additional Individuals with Variants in CHD3 and Literature Review.

Snijders Blok-Campeau syndrome (SNIBCPS, OMIM# 618205) is an extremely infrequent disease with only approximately 60 cases reported so far. SNIBCPS belongs to the group of neurodevelopmental disorders (NDDs). Clinical features of patients with SNIBCPS include global developmental delay, intellectual disability, speech and language difficulties and behavioral disorders like autism spectrum disorder. In addition, patients with SNIBCPS exhibit typical dysmorphic features including macrocephaly, hypertelorism, sparse eyebrows, broad forehead, prominent nose and pointed chin. The severity of the neurological effects as well as the presence of other features is variable among subjects. SNIBCPS is caused likely by pathogenic and pathogenic variants in CHD3 (Chromodomain Helicase DNA Binding Protein 3), which seems to be involved in chromatin remodeling by deacetylating histones. Here, we report 20 additional patients with clinical features compatible with SNIBCPS from 17 unrelated families with confirmed likely pathogenic/pathogenic variants in CHD3. Patients were analyzed by whole exome sequencing and segregation studies were performed by Sanger sequencing. Patients in this study showed different pathogenic variants affecting several functional domains of the protein. Additionally, none of the variants described here were reported in control population databases, and most computational predictors suggest that they are deleterious. The most common clinical features of the whole cohort of patients are global developmental delay (98%) and speech disorder/delay (92%). Other frequent features (51-74%) include intellectual disability, hypotonia, hypertelorism, abnormality of vision, macrocephaly and prominent forehead, among others. This study expands the number of individuals with confirmed SNIBCPS due to pathogenic or likely pathogenic variants in CHD3. Furthermore, we add evidence of the importance of the application of massive parallel sequencing for NDD patients for whom the clinical diagnosis might be challenging and where deep phenotyping is extremely useful to accurately manage and follow up the patients.

Case report: A novel pathogenic FRMD7 variant in a Turner syndrome patient with familial idiopathic infantile nystagmus.

Infantile idiopathic nystagmus (IIN) is an oculomotor disorder characterized by involuntary bilateral, periodic ocular oscillations, predominantly on the horizontal axis. X-linked IIN (XLIIN) is the most common form of congenital nystagmus, and the FERM domain-containing gene (FRMD7) is the most common cause of pathogenesis, followed by mutations in GPR143. To date, more than 60 pathogenic FRMD7 variants have been identified, and the physiopathological pathways leading to the disease are not yet completely understood. FRMD7-associated nystagmus usually affects male patients, while it shows incomplete penetrance in female patients, who are mostly asymptomatic but sometimes present with mild ocular oscillations or, occasionally, with clear nystagmus. Here we report the first case of a patient with Turner syndrome and INN in an XLIIN pedigree, in which we identified a novel frameshift mutation (c.1492dupT) in the FRMD7 gene: the absence of one X chromosome in the patient unmasked the presence of the familial genetic nystagmus.

Pediatric Slow-Progressive, but Not Non-Progressive Cerebellar Ataxia Delays Intra-Limb Anticipatory Postural Adjustments in the Upper Arm.

We recently investigated the role of the cerebellum during development, reporting that children with genetic slow-progressive ataxia (SlowP) show worse postural control during quiet stance and gait initiation compared to healthy children (H). Instead, children with genetic non-progressive ataxia (NonP) recalled the behavior of H. This may derive from compensatory networks, which are hindered by disease progression in SlowP while free to develop in NonP. In the aim of extending our findings to intra-limb postural control, we recorded, in 10 NonP, 10 SlowP and 10 H young patients, Anticipatory Postural Adjustments (APAs) in the proximal muscles of the upper-limb and preceding brisk index finger flexions. No significant differences in APA timing occurred between NonP and H, while APAs in SlowP were delayed. Indeed, the excitatory APA in Triceps Brachii was always present but significantly delayed with respect to both H and NonP. Moreover, the inhibitory APAs in the Biceps Brachii and Anterior Deltoid, which are normally followed by a late excitation, could not be detected in most SlowP children, as if inhibition was delayed to the extent where there was overlap with a late excitation. In conclusion, disease progression seems to be detrimental for intra-limb posture, supporting the idea that inter- and intra-limb postures seemingly share the same control mechanism.

Neurologic, Neuropsychologic, and Neuroradiologic Features of EBF3-Related Syndrome.

Background and Objectives: Heterozygous mutations or deletions of the EBF3 gene are known to cause a syndrome characterized by intellectual disability, neurodevelopmental disorders, facial dysmorphisms, hypotonia, and ataxia; the latter is quite common despite in most patients brain MRI is reported to be normal. Despite the predominant neurologic involvement of EBF3-related syndrome, a systematic definition of neurologic, cognitive/behavioral, and neuroradiologic features is lacking. Methods: We report on 6 patients (2 females and 4 males, age range 2-12 years), of whom 4 carrying a heterozygous point mutation of the EBF3 gene and 2 with 10q26 deletion encompassing the gene, diagnosed at Carlo Besta Neurologic Institute of Milan, Italy. Clinical evaluation was performed by a pediatric neurologist and pediatric dysmorphologist; ataxia severity was rated by Scale for the Assessment and Rating of Ataxia (SARA); brain MRIs were reviewed by expert neuroradiologists; general quotient levels were obtained through standardized Griffiths Mental Development Scales. Patients carrying a 10q26.3 deletion were diagnosed by array-CGH, whereas EBF3 variants were detected by whole exome sequencing. Results: Phenotype was consistent in all patients, but with wide variability in severity. Developmental milestones were invariably delayed and resulted in an extremely variable cognitive impairment. All patients showed ataxic signs, as confirmed by SARA scores, often associated with hypotonia. Brain MRI revealed in all children a cerebellar malformation with vermis hypoplasia and a peculiar foliation anomaly characterized by a radial disposition of cerebellar folia (dandelion sign). Neurophysiologic examinations were unremarkable. Discussion: EBF3-related syndrome has been so far described as a neurodevelopmental condition with dysmorphic traits, with limited emphasis on the neurologic features; we highlight the predominant neurologic involvement of these patients, which can be explained at least in part by the underlying cerebellar malformation. We therefore propose that EBF3-related syndrome should be classified and treated as a congenital, nonprogressive ataxia.

Rhythmic cortical myoclonus in patients with 6Q22.1 deletion.

DNA deletions involving 6q22.1 region result in developmental encephalopathy (DE), often associated with movement disorders and epilepsy. The phenotype is attributed to the loss of the NUS1 gene included in the deleted region. Here we report three patients with 6q22.1 deletions of variable length all showing developmental delay, and rhythmic cortical myoclonus. Two patients had generalized seizures beginning in infancy. Myoclonic jerks had polygraphic features consistent with a cortical origin, also supported by cortico-muscular coherence analysis displaying a significant peak around 20 Hz contralateral to activated segment. Deletions in 6q22.1 region, similarly to NUS1 loss-of-function mutations, give rise to DE and cortical myoclonus via a haploinsufficiency mechanism. A phenotype of progressive myoclonic epilepsy (PME) may also occur.

Periventricular heterotopia in a male child with USP9X missense variant.

The ubiquitin-specific protease USP9X has been found to play a role in multiple aspects of neural development including processes of neuronal migrations. In males, hemizygous partial loss of function variants in USP9X lead to a clinical phenotype primarily characterized by intellectual disability, hypotonia, speech and language impairment, behavioral disturbances accompanied by additional clinical features with variable expressivity. Structural brain abnormalities are reported in all cases where neuro-imaging was performed. The most common radiological features described include hypoplasia/agenesis of the corpus callosum, widened ventricles, white matter disturbances, and cerebellar hypoplasia. Here we report a child harboring a missense variant in USP9X presenting with the classical neurodevelopmental phenotype and a previously unreported radiological picture of periventricular heterotopia. This case expands the phenotypic landscape of this emergent condition and supports the critical role of USP9X in neuronal migration processes.

Expanding the genetics and phenotypic spectrum of Lysine-specific demethylase 5C (KDM5C): a report of 13 novel variants.

Lysine-specific demethylase 5C (KDM5C) has been identified as an important chromatin remodeling gene, contributing to X-linked neurodevelopmental disorders (NDDs). The KDM5C gene, located in the Xp22 chromosomal region, encodes the H3K4me3-me2 eraser involved in neuronal plasticity and dendritic growth. Here we report 30 individuals carrying 13 novel and one previously identified KDM5C variants. Our cohort includes the first reported case of somatic mosaicism in a male carrying a KDM5C nucleotide substitution, and a dual molecular finding in a female carrying a homozygous truncating FUCA1 alteration together with a de novo KDM5C variant. With the use of next generation sequencing strategies, we detected 1 frameshift, 1 stop codon, 2 splice-site and 10 missense variants, which pathogenic role was carefully investigated by a thorough bioinformatic analysis. The pattern of X-chromosome inactivation was found to have an impact on KDM5C phenotypic expression in females of our cohort. The affected individuals of our case series manifested a neurodevelopmental condition characterized by psychomotor delay, intellectual disability with speech disorders, and behavioral features with particular disturbed sleep pattern; other observed clinical manifestations were short stature, obesity and hypertrichosis. Collectively, these findings expand the current knowledge about the pathogenic mechanisms leading to dysfunction of this important chromatin remodeling gene and contribute to a refinement of the KDM5C phenotypic spectrum.

Phenotypic spectrum of the recurrent TRPM3 p.(Val837Met) substitution in seven individuals with global developmental delay and hypotonia.

TRPM3 encodes a transient receptor potential cation channel of the melastatin family, expressed in the central nervous system and in peripheral sensory neurons of the dorsal root ganglia. The recurrent substitution in TRPM3: c.2509G>A, p.(Val837Met) has been associated with syndromic intellectual disability and seizures. In this report, we present the clinical and molecular features of seven previously unreported individuals, identified by exome sequencing, with the recurrent p.(Val837Met) variant and global developmental delay. Other shared clinical features included congenital hypotonia, dysmorphic facial features (broad forehead, deep-set eyes, and down turned mouth), exotropia, and musculoskeletal issues (hip dysplasia, hip dislocation, scoliosis). Seizures were observed in two of seven individuals (febrile seizure in one and generalized tonic-clonic seizures with atonic drops in another), and epileptiform activity was observed in an additional two individuals. This report extends the number of affected individuals to 16 who are heterozygous for the de novo recurrent substitution p.(Val837Met). In contrast with the initial report, epilepsy was not a mandatory feature observed in this series. TRPM3 pathogenic variation should be considered in individuals with global developmental delays, moderate-severe intellectual disability with, or without, childhood-onset epilepsy.

A Missense De Novo Variant in the CASK-interactor KIRREL3 Gene Leading to Neurodevelopmental Disorder with Mild Cerebellar Hypoplasia.

KIRREL3 is a gene important for the central nervous system development-in particular for the process of neuronal migration, axonal fasciculation, and synaptogenesis-and colocalizes and cooperates in neurons with CASK gene. Alterations of KIRREL3 have been linked to neurodevelopmental disorders, ranging from developmental delay, to autism spectrum disorder, to attention deficit/hyperactivity disorder. The underlying mechanism is not yet fully understood, as it has been hypothesized a fully dominant effect, a risk factor role of KIRREL3 partially penetrating variants, and a recessive inheritance pattern. We report a novel and de novo KIRREL3 mutation in a child affected by severe neurodevelopmental disorder and with brain magnetic resonance imaging evidence of mega cisterna magna and mild cerebellar hypoplasia. This case strengthens the hypothesis that dominant KIRREL3 variants may lead to neurodevelopmental disruption; furthermore, given the strong interaction between KIRREL3 and CASK, we discuss as posterior fossa anomalies may also be part of the phenotype of KIRREL3-related syndrome.

Expanding the PURA syndrome phenotype: A child with the recurrent PURA p.(Phe233del) pathogenic variant showing similarities with cutis laxa.

BACKGROUND: PURA syndrome is rare autosomal dominant condition characterized by moderate to severe neurodevelopmental delay with absence of speech in nearly all patients and lack of independent ambulation in many. Early-onset problems include excessive hiccups, hypotonia, hypersomnolence, hypothermia, feeding difficulties, recurrent apneas, epileptic seizures, and abnormal nonepileptic movements. Other less common manifestations comprise congenital heart defects, urogenital malformations, and various skeletal, ophthalmological, gastrointestinal, and endocrine anomalies. Up to now, 78 individuals with PURA syndrome and 64 different pathogenic variants have been reported, but no clear-cut genotype-phenotype correlations have emerged so far. Herein, we report the clinical and molecular characterization of a 3-year-old girl with severe hypotonia, global developmental delay, and soft, loose skin, who came to our attention with a suspicion of cutis laxa (CL), which denotes another condition with variable neurodevelopmental problems. METHODS: Amplicon-based whole exome sequencing was performed, and an in-house pipeline was used to conduct filtering and prioritization of variants. New prediction algorithms for indels were used to validate the pathogenicity of the PURA variant, and results were confirmed with the Sanger method. Finally, we collected clinical and mutational data of all PURA syndrome patients reported yet and compared the clinical features with those of our patient. RESULTS: Clinical evaluation and biochemical investigations excluded CL and prompted to perform whole exome sequencing, which confirmed the absence of pathogenic variants in all CL-related genes and revealed the known PURA c.697_699del, p.(Phe233del) variant, identified hitherto in seven additional children with PURA syndrome. CONCLUSIONS: Our data expand the phenotypic spectrum of PURA syndrome by showing that it can be regarded as a differential diagnosis for cutis laxa in early infancy. Our patient and literature review emphasize that a wide clinical variability exists not only between individuals with different PURA variants, but also among patients with the same causal mutation.

Milder presentation of TELO2-related syndrome in two sisters homozygous for the p.Arg609His pathogenic variant.

Biallelic loss of function of TELO2 gene cause a severe syndromic disease mainly characterized by global developmental delay with poor motor and language acquisitions, microcephaly, short stature, minor facial and limbs anomalies, sleep disorder, spasticity, and balance impairment up to ataxia. TELO2-related syndrome, also known as You-Hoover-Fong Syndrome, is extremely rare and since its first description in 2016 only 8 individuals have been reported, all showing a severe disability. The causative gene is member of the big molecular family of genes responsible for cells proliferation and DNA stability. We describe the case of two sisters, carrying the homozygous p. Arg609His variant of the gene, who present a milder phenotype of TELO2-related syndrome. Such variant has been reported once in a more severely affected patient, in compound heterozygous state associated with the p. Pro260Leu variant, suggesting a possible role of the p. Arg609His variant in determining milder phenotypes. Comparing the siblings with all previously reported cases, we offer an overview on the condition and discuss TELO2 genetic interactions, in order to further explore the molecular bases of this recently described disorder.

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.

Severe Phenotype in a Patient With Homozygous 15q21.2 Microdeletion Involving BCL2L10, GNB5, and MYO5C Genes, Resembling Infantile Developmental Disorder With Cardiac Arrhythmias (IDDCA).

Homozygous and compound heterozygous mutations in GNB5 gene have been associated with a wide spectrum of clinical presentations, ranging from neurodevelopmental issues with or without cardiac arrhythmia (LADCI) to severe developmental delay with epileptic encephalopathy, retinal dystrophy, and heart rhythm abnormalities (IDDCA). While missense or missense/non-sense mutations usually lead to milder form, the biallelic loss of function of GNB5 gene causes the severe multisystemic IDDCA phenotype. So far, only 27 patients have been described with GNB5-associated disease. We report the first case of a patient carrying a homozygous 15q21.2 microdeletion, encompassing GNB5 and the two contiguous genes BCL2L10 and MYO5C. The clinical features of the child are consistent with the severe IDDCA phenotype, thus confirming the GNB5 loss-of-function mechanism in determining such presentation of the disease.

Chromosomal Microarray Analysis Has a Poor Diagnostic Yield in Children with Developmental Delay/Intellectual Disability When Concurrent Cerebellar Anomalies Are Present.

Chromosomal microarray analysis is commonly used as screening test for children with neurodevelopmental issues, also in case of complex neurological phenotypes. Developmental delay/intellectual disability is a common presentation sign in pediatric ataxias, diseases with high clinical and genetic heterogeneity. In order to determine the diagnostic yield of Array-CGH in such conditions, all the tests performed in the last 10-year activity of a single referral center in children who present, besides the neurodevelopmental impairment, cerebellar abnormalities have been systematically gathered. The study demonstrates that, except for Dandy-Walker malformation or poly-malformative phenotypes, chromosomal microarray analysis should be discouraged as first-line diagnostic test in pediatric ataxias with neurodevelopmental disability.

A Novel WAC Loss of Function Mutation in an Individual Presenting with Encephalopathy Related to Status Epilepticus during Sleep (ESES).

WAC (WW Domain Containing Adaptor With Coiled-Coil) mutations have been reported in only 20 individuals presenting a neurodevelopmental disorder characterized by intellectual disability, neonatal hypotonia, behavioral problems, and mildly dysmorphic features. Using targeted deep sequencing, we screened a cohort of 630 individuals with variable degrees of intellectual disability and identified five WAC rare variants: two variants were inherited from healthy parents; two previously reported de novo mutations, c.1661_1664del (p.Ser554*) and c.374C>A (p.Ser125*); and a novel c.381+2T>C variant causing the skipping of exon 4 of the gene, inherited from a reportedly asymptomatic father with somatic mosaicism. A phenotypic evaluation of this individual evidenced areas of cognitive and behavioral deficits. The patient carrying the novel splicing mutation had a clinical history of encephalopathy related to status epilepticus during slow sleep (ESES), recently reported in another WAC individual. This first report of a WAC somatic mosaic remarks the contribution of mosaicism in the etiology of neurodevelopmental and neuropsychiatric disorders. We summarized the clinical data of reported individuals with WAC pathogenic mutations, which together with our findings, allowed for the expansion of the phenotypic spectrum of WAC-related disorders.