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SPG6, caused by NIPA1 (nonimprinted in Prader-Willi/Angelman syndrome) gene pathogenic variants, is mainly considered as a pure autosomal dominant hereditary spastic paraplegia (AD-HSP), even if descriptions of complex cases have also been reported. We detected the common c.316G > A, p.(Gly106Arg) pathogenic de novo substitution in a 10-year-old patient with HSP and drug-resistant eyelid myoclonia with absences. In order to assess the significance of this association, we reviewed the literature to find that 25/110 (23%) SPG6 cases are complex, including a heterogeneous spectrum of comorbidities, in which epilepsy is most represented (10%), but also featuring peripheral neuropathy (5.5%), amyotrophic lateral sclerosis (3.6%), memory deficits (3.6%) or cognitive impairment (2.7%), tremor (2.7%) and dystonia (0.9%). From this literature review and our single case experience, two main conclusions can be drawn. First, SPG6 is an AD-HSP with both pure and complex presentation, and frequent occurrence of epilepsy within the spectrum of genetic generalized epilepsies (absences, bilateral tonic-clonic, bilateral tonic-clonic with upper limbs myoclonic seizures and eyelid myoclonia with absences). Second, opposed to previous descriptions, seizures might not always be drug responsive.

Although neurobeachin (NBEA) de novo genetic variants have been mainly reported in patients with neurodevelopmental disorders (NDD), they have also been recently associated with early childhood epilepsy. We report an 11-year-old boy who was first evaluated at 34 months of age because of drug-resistant epileptic encephalopathy. He also had developmental delay and prominent autistic features. Whole-exome sequencing (WES) disclosed a pathogenic NBEA c.5258_5279del, p.(Ala1753Valfs*13) variant, occurring de novo and a paternally-inherited heterozygous NBEA c.416T>C p.(Met139Thr) variant of uncertain significance (VUS). The patient showed good response to the ketogenic diet, suggesting that this therapy may be an effective option for patients with seizures who carry NBEA variants.

Abnormal breathing patterns are a typical feature of Rett and Pitt-Hopkins syndrome and their variants. Their treatment can be challenging, with a risk of long-term detrimental consequences. Early infantile epileptic encephalopathy (EIEE) type 54 is a rare epileptic encephalopathy caused by pathogenic variants in the heterogeneous nuclear ribonucleoprotein U (HNRNPU) gene. Only one case has been described in the literature with episodes of hyperventilation and apnea, but treatment was not discussed. We describe the clinical and genetic features and treatment strategies in a case of EIEE type 54 and severely abnormal breathing pattern. A novel and likely pathogenic c.2277dup, p.(Pro760Serfs*5) variant in the HNRNPU gene was found in a male patient with severe episodes of hyperventilation and apnea, leading to syncope. Combination therapy with acetazolamide, alprazolam and aripiprazole led to significant clinical improvement. Although HNRNPU has not been implicated in breathing control, pathogenic variants in this gene can be associated with the development of abnormal breathing patterns reminiscent of Rett and Pitt-Hopkins syndrome. Its function as a gene expression regulator and its interaction with transcription factors offers a potential pathogenetic link between these 3 disorders. Based on our experience, treatment strategies can be similar to those already applied for patients with Pitt-Hopkins and Rett syndrome.

The CAMK2B gene encodes the β-subunit of calcium/calmodulin-dependent protein kinase II (CAMK2), an enzyme that has crucial roles in synaptic plasticity, especially in hippocampal and cerebellar neurons. Heterozygous variants in CAMK2B cause a rare neurodevelopmental disorder, with 40% of the reported cases sharing the same variant: c.416C>T, p.(P139L). This case report describes a 22-year-old patient with this recurrent variant, who presents with severe intellectual disability, absence of language, hypotonia, microcephaly, dysmorphic features, epilepsy, behavioral abnormalities, motor stereotypies, optic atrophy, and progressive cerebellar atrophy. Notably, this patient is the oldest reported so far and allows us to better delineate the clinical phenotype associated with this variant, adding clinical aspects never described before, such as epilepsy, optic atrophy, scoliosis, and neuroradiological changes characterized by progressive cerebellar atrophy.

The term “arthrogryposis” is used to indicate multiple congenital contractures affecting two or more areas of the body. Arthrogryposis is the consequence of an impairment of embryofetal neuromuscular function and development. The causes of arthrogryposis are multiple, and in newborns, it is difficult to predict the molecular defect as well as the clinical evolution just based on clinical findings. We studied a consecutive series of 13 participants who had amyoplasia, distal arthrogryposis (DA), or syndromic forms of arthrogryposis with normal intellectual development and other motor abilities. The underlying pathogenic variants were identified in 11 out of 13 participants. Correlating the genotype with the clinical features indicated that prenatal findings were specific for DA; this was helpful to identify familial cases, but features were non-specific for the involved gene. Perinatal clinical findings were similar among the participants, except for amyoplasia. Dilatation of the aortic root led to the diagnosis of Loeys–Dietz syndrome (LDS) in one case. The phenotype of DA type 5D (DA5D) and Escobar syndrome became more characteristic at later ages due to more pronounced pterygia. Follow-up indicated that DA type 1 (DA1)/DA type 2B (DA2B) spectrum and LDS had a more favorable course than the other forms. Hand clenching and talipes equinovarus/rocker bottom foot showed an improvement in all participants, and adducted thumb resolved in all forms except in amyoplasia. The combination of clinical evaluation with Next Generation Sequencing (NGS) analysis in the newborn may allow for an early diagnosis and, particularly in the DAs, suggests a favorable prognosis.

Background: Charcot–Marie–Tooth (CMT) is the most frequent group of inherited neuropathies and includes several heterogeneous phenotypes. Over 80 causative genes have been described so far. Variants in the microrchidia family CW-type zinc finger 2 (MORC2) gene have been described in several axonal polyneuropathy (CMT2) patients with childhood or adult onset. Occasionally more complex phenotypes with delayed milestones, severe hypotonia, intellectual disability, dystonic postures, pyramidal signs, and neuroimaging abnormalities have been reported.Case Presentation: We report on a patient with a de novo MORC2 gene variant (c.1181A>G p.Tyr394Cys) with a history of developmental delay, axial hypotonia, progressive gait disorder with dystonic features, and intentional tremor. At the age of 8 years, he showed bilateral pyramidal signs (clonus, increased tendon reflexes, and Babinski sign) and bilateral pes cavus. The first neuroimaging performed at the age of 3 years demonstrated white matter abnormalities in the posterior periventricular zone, in the frontal lobes bilaterally and at the midbrain, stable during childhood and adolescence. Nerve conduction studies (NCS) were negative until the age of 15 years, when a sensory axonal neuropathy appeared. The association between pyramidal signs and neuropathy due to the MORC2 gene variant is increasingly being highlighted, although a neuroradiological correlate is evident only in about half of the cases. Longitudinal nerve conduction velocity (NCV) are helpful to identify late-onset features and provide useful information for diagnosis in patients with rare neurogenetic disorders.Conclusions: Characterization of complex neurological disorders is important to delineate the expanding phenotypic spectrum of MORC2-related disease, to confirm if possible the pathogenicity of the variants and to deepen the genotype–phenotype correlation.

Autosomal recessive spinocerebellar ataxia type 18 (SCAR18) is caused by pathogenic variants in the Glutamate Receptor, Ionotropic, Delta-2 (GRID2) gene. We describe the long-term follow-up from 1 to 31 years of an Italian patient with congenital SCAR18 who is compound heterozygous for a maternally-inherited nonsense variant and a de novo microdeletion. To date, this is the longest follow-up in congenital SCAR18.

Background Pathogenic variants in KIF1A (kinesin family member 1A) gene have been associated with hereditary spastic paraplegia (HSP) type 30 (SPG30), encopassing autosomal dominant and recessive, pure and complicated forms. Case presentation We report the long-term follow-up of a 19 years-old boy first evaluated at 18 months of age because of toe walking and unstable gait with frequent falls. He developed speech delay, mild intellectual disability, a slowly progressive pyramidal syndrome, microcephaly, bilateral optic subatrophy and a sensory axonal polyneuropathy. Brain MRI showed cerebellar atrophy, stable along serial evaluations (last performed at 18 years of age). Targeted NGS sequencing disclosed the de novo c.914C > T missense, likely pathogenic variant on KIF1A gene. Conclusions We report on a previously unpublished de novo heterozygous likely pathogenic KIF1A variant associated with slowly progressive complicated SPG30 and stable cerebellar atrophy on long-term follow-up, adding to current knowledge on this HSP subtype.

Background Molecular technologies are expanding our knowledge about genetic variability underlying early-onset non-progressive choreic syndromes. Focusing on NKX2-1-related chorea, the clinical phenotype and sleep related disorders have been only partially characterized. Methods We propose a retrospective and longitudinal observational study in 7 patients with non-progressive chorea due to NKX2-1 mutations. In all subjects sleep and awake EEG, brain MRI with study of pituitary gland, chest X-rays, endocrinological investigations were performed. Movement disorders, pattern of sleep and related disorders were investigated using structured clinical evaluation and several validated questionnaires. Results In patients carrying NKX2-1 mutations, chorea was mainly distributed in the upper limbs and tended to improve with age. All patients presented clinical or subclinical hypothyroidism and delayed motor milestones. Three subjects had symptoms consistent with Restless Legs Syndrome (RLS) that improved with Levodopa. Conclusions Patients with NKX2-1 gene mutations should be investigated for RLS, which, similarly to chorea, can sometimes be ameliorated by Levodopa.

We aimed to identify clinical, molecular and radiological correlates of activities of daily living (ADL) in patients with cerebellar atrophy caused by PMM2 mutations (PMM2-CDG), the most frequent congenital disorder of glycosylation. Twenty-six PMM2-CDG patients (12 males; mean age 13 ± 11.1 years) underwent a standardized assessment to measure ADL, ataxia (brief ataxia rating scale, BARS) and phenotype severity (Nijmegen CDG rating scale, NCRS). MRI biometry of the cerebellum and the brainstem were performed in 23 patients (11 males; aged 5 months–18 years) and 19 control subjects with equal gender and age distributions. The average total ADL score was 15.3 ± 8.5 (range 3–32 out of 36 indicating severe functional disability), representing variable functional outcome in PMM2-CDG patients. Total ADL scores were significantly correlated with NCRS (r2 = 0.55, p < 0.001) and BARS scores (r2 = 0.764; p < 0.001). Severe intellectual disability, peripheral neuropathy, and severe PMM2 variants were all significantly associated with worse functional outcome. Higher ADL scores were significantly associated with decreased diameters of cerebellar vermis (r2 = 0.347; p = 0.004), hemispheres (r2 = 0.436; p = 0.005), and brainstem, particularly the mid-pons (r2 = 0.64; p < 0.001) representing the major radiological predictor of functional disability score in multivariate regression analysis. We show that cerebellar syndrome severity, cognitive level, peripheral neuropathy, and genotype correlate with ADL used to quantify disease-related deficits in PMM2-CDG. Brainstem involvement should be regarded among functional outcome predictors in patients with cerebellar atrophy caused by PMM2-CDG.

Bartter syndrome (BS) is a rare autosomal recessive renal tubular disorder characterized by acute electrolyte imbalance, and similarly, osmotic demyelination syndrome (ODS) is a rather rare complication occurring during electrolyte imbalance. The pathological features of ODS include central pontine myelinolysis and extrapontine myelinolysis (EPM), which consist of severe damage to the myelin sheath of neurons. ODS is very rare in children. We describe a case of a 3-month-old infant with ODS and EPM associated with undiagnosed BS. ODS developed because of a sudden change in electrolyte levels and osmolality caused by acute dehydration during a gastrointestinal infection episode. Undiagnosed, untreated, and non-balanced BS was the cause of the neurological complication. Our patient represents the first case of ODS in BS, the ninth case of ODS in an infant less than one year old, and the third case of isolated EPM in such a young patient. This case report reminds us that in rare diseases, young patients tend to have genetic components.

Schwartz–Jampel syndrome type 1 (SJS1) is an autosomal recessive chondrodystrophic myotonia, linked to heparan sulfate proteoglycan 2 (HSPG2) variants. We describe a patient with typical features of SJS1, but not obesity. Clinical exome sequencing detected a rare missense variant in HSPG2, confirming our clinical diagnosis, but also two homozygous variants in SDC3 and ADRB3 genes, previously described to be associated with obesity. This additional genetic result could better explain our patient's phenotype. Despite the phenotypic variability associated to HSPG2 variants, it is advisable to carefully check other possible genetic causes underlying clinical signs not strictly related to the classical phenotype of SJS1.

Pathogenic variants in phosphatidylinositol glycan anchor biosynthesis class B (PIGB) gene have been first described as the cause of early infantile epileptic encephalopathy 80 (EIEE-80) in 2019. This disorder, an inherited glycosylphosphatidylinositol deficiency, is associated with a complex neurologic phenotype, including developmental delay, early-onset epilepsy and peripheral neuropathy. We report on a 5 year-old girl born from consanguineous parents, manifesting severe global developmental delay with absent speech, mixed peripheral polyneuropathy, hypotonia, bilateral equino-varo-supinated-cavus foot, early-onset scoliosis, elevated serum alkaline phosphatase and a single episode of febrile status epilepticus. Hypomyelination was documented on brain MRI. Whole-exome sequencing (WES) disclosed the likely pathogenic biallelic PIGB NM_004855.4: c.463G > C, p.(Asp155His) missense variant. In our patient, while other characteristic clinical, neuroimaging and laboratory findings (as described in the first research paper) were present, seizures were not a major clinical issue, thus contributing to our knowledge on this ultra-rare disorder.

Background: Niemann-Pick disease type C (NPC) is a lysosomal storage disease caused by mutations in NPC1 or NPC2 genes. Case presentation: We present two brothers with the same compound heterozygous variants in exon 13 of the NPC1 gene (18q11.2), the first one (c.1955C> G, p. Ser652Trp), inherited from the mother, the second (c.2107T>A p.Phe703Ile) inherited from the father, associated to the classical biochemical phenotype of NPC. The two brothers presented unspecific neurologic symptoms with difference in age of onset: one presented and previously described dyspraxia and motor clumsiness at age 7 years, the other showed a systemic presentation with hepatosplenomegaly noted at the age of two months and neurological symptoms onset at age 4 with speech disturbance. Clinical evolution and neuroimaging data led to the final diagnosis. Systemic signs did not correlate with the onset of neurological symptoms. Miglustat therapy was started in both patients. Conclusions: We highlight the extreme phenotypic heterogeneity of NP-C in the presence of the same genetic variant and the unspecificity of neurologic signs at onset as previously reported. We report some positive effects of miglustat on disease progression assessed also with neuropsychological follow-up, with an age-dependent response.

International audience; Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control neuronal excitability and their dysfunction has been linked to epileptogenesis but few individuals with neurological disorders related to variants altering HCN channels have been reported so far. In 2014, we described five individuals with epileptic encephalopathy due to de novo HCN1 variants. To delineate HCN1-related disorders and investigate genotype-phenotype correlations further, we assembled a cohort of 33 unpublished patients with novel pathogenic or likely pathogenic variants: 19 probands carrying 14 different de novo mutations and four families with dominantly inherited variants segregating with epilepsy in 14 individuals, but not penetrant in six additional individuals. Sporadic patients had epilepsy with median onset at age 7 months and in 36% the first seizure occurred during a febrile illness. Overall, considering familial and sporadic patients, the predominant phenotypes were mild, including genetic generalized epilepsies and genetic epilepsy with febrile seizures plus (GEFS+) spectrum. About 20% manifested neonatal/infantile onset otherwise unclassified epileptic encephalopathy. The study also included eight patients with variants of unknown significance: one adopted patient had two HCN1 variants, four probands had intellectual disability without seizures, and three individuals had missense variants inherited from an asymptomatic parent. Of the 18 novel pathogenic missense variants identified, 12 were associated with severe phenotypes and clustered within or close to transmembrane domains, while variants segregating with milder phenotypes were located outside transmembrane domains, in the intracellular N- and C-terminal parts of the channel. Five recurrent variants were associated with similar phenotypes. Using whole-cell patch-clamp, we showed that the impact of 12 selected variants ranged from complete loss-of-function to significant shifts in activation kinetics and/or voltage dependence. Functional analysis of three different substitutions altering Gly391 revealed that these variants had different consequences on channel biophysical properties. The Gly391Asp variant, associated with the most severe, neonatal phenotype, also had the most severe impact on channel function. Molecular dynamics simulation on channel structure showed that homotetramers were not conducting ions because the permeation path was blocked by cation(s) strongly complexed to the Asp residue, whereas heterotetramers showed an instantaneous current component possibly linked to deformation of the channel pore. In conclusion, our results considerably expand the clinical spectrum related to HCN1 variants to include common generalized epilepsy phenotypes and further illustrate how HCN1 has a pivotal function in brain development and control of neuronal excitability.

This is a report of a child with the 47,XYY karyotype and bilateral high-intensity focal lucencies in the periventricular white matter upon magnetic resonance imaging. We discuss the significance of these findings with respect to possible etiologies, and conclude that they may be characterized as giant perivascular spaces. To our knowledge, this is the first demonstration of giant perivascular spaces concurrent with the aberrant 47,XYY karyotype. Evidence of large perivascular spaces in children requires particular caution because they could cause obstruction of the cerebrospinal fluid outflow. Although giant perivascular spaces may be found in inflammatory brain disease, perivascular myelin pathology or obstruction of lymphatic drainage, extended clinical and laboratory investigation and a detailed chromosomal analysis are always recommended when this rather frequent neuroradiological finding is encountered in children.

Background Mutations in the gene PRRT2 have been identified in a variety of early-onset paroxysmal disorders. To date associations between PRRT2 mutations and benign myoclonus of early infancy have not been reported. Clinical report We describe a baby affected by PRRT2 mutation and benign infantile epilepsy, with an episode of focal status epilepticus. During follow-up he developed benign myoclonus of early infancy. Discussion We hypothesize a pathogenic role of PRRT2 mutation in inducing benign myoclonus of early infancy, similarly to that at the origin of other PRRT2-related paroxysmal movement disorders, such as paroxysmal kinesigenic dyskinesia. Conclusions Currently the function of PRRT2 is poorly understood, even if a marked pleiotropy and variable penetrance of its mutations are well known. Our case concurs in expanding the broad clinical spectrum of PRRT2-related disorders.

KCNQ2 encephalopathy is characterized by severely abnormal EEG, neonatal-onset epilepsy and developmental delay. It is caused by mutations (typically missense) in the KCNQ2 gene, encoding the voltage gated potassium channel Kv7.2 and leading to a negative-dominant effect. We present one case experiencing recurrent neonatal seizures with changing hemispheres of origin, reminiscent of epilepsy of infancy with migrating focal seizures. At 9months of age the patient is still seizure-free on carbamazepine, although he is developing a spastic-dystonic tetraplegia with severe dysphagia. He harbors a de novo deletion (c.913_915del [p.Phe305del)]), only described once in a couple of severely affected twins, and leading to the deletion of a phenylalanine residue in the pore domain of the channel. In conclusion, our case is the second described with encephalopathy due to this specific deletion (the one and only deletion so far reported in KCNQ2 encephalopathy). Thus, deletion is a newly described mechanism highlighting how not only missense mutations but also deletions in the channel hot spots can lead to a severe phenotype. Furthermore he presented ictal EEG features similar to epilepsy of infancy with migrating focal seizures not previously described.

Background and aim of the work: Childhood-onset peripheral neuropathies are often of genetic origin. Charcot-Marie-Tooth (CMT), is considered the commonest neuromuscular disorder. Due to its high clinical heterogeneity, especially in the pediatric age, the co-existence of central and peripheral symptoms and signs does not necessarily rule out a diagnosis of hereditary peripheral neuropathy. Methods: We describe the clinical, neurophysiological and genetic findings in a teen-age patient evaluated for acquired toe-walking and progressive difficulties in walking since the age of 5. Genetic testing was carried out with a targeted NGS panel. Identified variants are analyzed using Variant Studio program (Illumina). Rare variants and variants considered as pathogenic were analyzed by Sanger direct sequencing. Results: The coexistence ofperipheral and pyramidal signs in the lower limbs, the absence of a significant pre/perinatal history, the unremarkable brain and spine MRI, together with the presence of a sensory-motor polyneuropathy in all four limbs, prompted the execution of genetic investigations with an NGS panel covering hereditary spastic paraplegias, motor neuron disease and Charcot-Marie-Tooth. We identified a previously undescribed variant (c.1142G>T, p.Arg381Leu) in the EGR2 gene. Conclusions:ERG2 gene has been described as a cause of various phenotypes, including a rare autosomal dominant form of CMT (CMT type 1D) representing approximately 1% of all CMT subgroups. We describe a novel pathogenic variant in EGR2 gene leading to the development of a complex association of peripheral and central neurological signs, underscoring the genetic and clinical heterogeneity of hereditary neuropathies of pediatric onset. (www.actabiomedica.it)

Myotonia is rare in newborns, and not well-known. Mutations of the skeletal muscle sodium channel gene SCN4A are associated with several neuromuscular disorders including sodium channel myotonias. We reported a 4-year-old female who presented with diffuse stiffness, bilateral clubfoot, hip dislocation, facial dysmorphisms and myotonia at birth. At 4 years of age the neurological examination showed characteristic “Hercules-like appearance” hyporeflexia, mild grip myotonia and bilateral pes cavus. The stiffness was worst at rest and in the early morning which improves with exercise. The clinical features, electromyography findings and diagnostic work-up of this patient and of child’s mother were described. The clinical follow-up led us to the diagnosis of sodium channel myotonia with atypical neonatal onset. Mutation analysis in the patient and in child’s mother revealed a novel heterozygous p.N1180I mutation in exon 19 of SCN4A gene. We recommend that in newborns with stiffness, peripheral contractures and myotonia, the sequence analysis of SCN4A gene should be performed.

We report on a patient with terminal deletion of the long arm of chromosome 14 displaying brain interhemispheric fusion limited to the midline anterior frontal cortex associated with hypoplastic corpus callosum and incomplete rotation of the left hippocampus in a clinical setting of motor and intellectual disability with poor language, and social behavior abnormalities with aggressiveness. Some possible correlations between clinical signs and symptoms and various aspects of the complex brain malformation are briefly discussed and compared with other known abnormalities of chromosome 14. The different neuropathology of the most common forms and the new forms of holoprosencephaly recently described is also discussed and leads us to suggest classifying the interhemispheric fusion of this case as a "minimal" form of holoprosencephaly. This appears to be the first description in a 14q deletion patient.

Infantile neuroaxonal dystrophy is a rare neurodegenerative disorder characterized by infantile onset of rapid motor and cognitive regression and hypotonia evolving into spasticity. Recessively inherited mutations of the PLA2G6 gene are causative of infantile neuroaxonal dystrophy and other PLA2G6-associated neurodegeneration, which includes conditions known as atypical neuroaxonal dystrophy, Karak syndrome and early-onset dystonia-parkinsonism with cognitive impairment. Phenotypic spectrum continues to evolve and genotype-phenotype correlations are currently limited. Due to the overlapping phenotypes and heterogeneity of clinical findings characterization of the syndrome is not always achievable. We reviewed the most recent clinical and neuroradiological information in the way to make easier differential diagnosis with other degenerative disorders in the paediatric age. Recognizing subtle signs and symptoms is a fascinating challenge to drive towards better diagnostic and genetic investigations.

We report the first case of a child with recessive hereditary methemoglobinemia type II with demonstrated cerebellar atrophy. This very rare blood disorder results in mild cyanosis, profound mental and motor impairment, and movement disorders in infancy and childhood. We suggest that children with unexplained severe encephalopathy and cerebellar atrophy should also be tested for hereditary methemoglobinemia type II.

Infantile neuroaxonal dystrophy is a rare neurodegenerative disorder, with onset in the first or second year of life. Mutations in the PLA2G6 gene encoding iPLA2-VI, a calcium-independent phospholipase, have been identified in these children. In classic infantile neuroaxonal dystrophy–affected children, psychomotor regression is the most frequent presentation, usually with ataxia and optic atrophy, followed by the development of tetraparesis. We report a child carrying a homozygous mutation in the PLA2G6 gene with neonatal onset of disease and somewhat different clinical phenotype such as severe congenital hypotonia, marked weakness, and bulbar signs suggesting that infantile neuroaxonal dystrophy can start at birth with atypical phenotype.