Mental deficiency, alterations in performance, and CNS abnormalities in overgrowth syndromes

Surgical Management of Overgrowth Syndrome With Bilateral Vision-Threatening Ptosis

We describe the first case reported in ophthalmological literature of the surgical management of a 17-month-old boy with bilateral vision-threatening ptosis, tarsomegaly, ectropion, and euryblepharon secondary to suspected overgrowth syndrome. We elaborate on the major challenges associated with surgical management including the natural and asymmetric growth of oversized tissue, the high likelihood of scarring and formation of disorganized tissue, and risks of frequent intubation in these patients who may have lesions that compromise critical structures such as the airway. Ultimately, surgical intervention is encouraged primarily if vision or ocular health is threatened and secondarily to achieve good cosmesis.

Fetal macrocephaly: Pathophysiology, prenatal diagnosis and management

Macrocephaly means a large head and is defined as a head circumference (HC) above the 98th percentile or greater than +2SD above the mean for gestational age. Macrocephaly can be primary and due to increased brain tissue (megalocephaly), which in most cases is familial and benign or secondary. The latter may be due to various causes, including but not limited to communicating or non-communicating hydrocephalus, cerebral edema, focal and pericerebral increased fluid collections, thickened calvarium and brain tumors. Megalocephaly can be syndromic or non-syndromic. In the former, gyral and structural CNS anomalies are common. It is important to exercise caution when considering a diagnosis of megalocephaly due to limitations in the accuracy of HC measurement, lack of nomograms for specific populations, inconsistencies between prenatal and postnatal HC growth curves and progression over time. The degree of macrocephaly is important, with mild macrocephaly ≤2.5SD carrying a good prognosis, especially when one of the parents has macrocephaly and normal development. Cases in which the patient history and/or physical exam are positive or when parental HC are normal are more worrisome and warrant a neurosonogram, fetal MRI and genetic testing to better delineate the underlying etiology and provide appropriate counseling.

Neonatal Sotos Syndrome: A Novel Frameshift Mutation of the NSD1 Gene Associated with Neonatal Encephalopathy Presenting without Overgrowth

Sotos syndrome type I is one of the more common genetic overgrowth disorders. It presents classically with macrocephaly, distinctive facial gestalt, and acromegalic features, along with neonatal complications including hypotonia, feeding difficulties, and hypoglycemia with other minor feature inconstancies. The phenotypical overlap of features of this syndrome, more so in neonatal age, thwarts an easy diagnosis. In this case report, a neonate of a nonconsanguineous marriage to a multigravida mother with insignificant obstetric history, presented primarily with respiratory difficulty, central hypotonia, and hypoglycemia. Sparse hair, tall forehead, pointed chin, and lax skin were accompanied by persistent encephalopathy and refractory myoclonic jerks. However, the quintessential features of pre- and postnatal overgrowth were lacking, making the line of diagnosis difficult. On neuroimaging, atypical diffuse pachygyria was found. Clinical exome sequencing revealed heterozygous single base pair deletion in exon 21 of the NSD1 gene on chromosome 5q35, resulting in an unreported frameshift and premature truncation of the protein 19 amino acids downstream to codon 2065, confirming the genetic diagnosis of autosomal dominant Sotos syndrome 1. The neonate later succumbed to death after withdrawal of ventilatory support.

Clinical Phenotype and Bone Biopsy Characteristics in a Child with Proteus Syndrome

Proteus syndrome is a rare genetic disorder, which is characterized by progressive, segmental, or patchy overgrowth of diverse tissues of all germ layers, including the skeleton. Here, we present a 9-year-old girl with a somatic-activating mutation (c.49G > A; p.Glu17Lys) in AKT1 gene in a mosaic status typical for Proteus syndrome. She presented with hemihypertrophy of the right lower limb and a "moccasin" lesion among others. A transiliac bone biopsy was analyzed for bone histology/histomorphometry as well as bone mineralization density distribution (BMDD) and osteocyte lacunae sections (OLS) characteristics based on quantitative backscattered electron imaging. Bone histomorphometry revealed highly increased mineralizing surface (Z-score + 2.3) and mineral apposition rate (Z-score + 19.3), no osteoclasts (Z-score - 2.1), and an increased amount of primary bone in the external cortex. BMDD abnormalities included a decreased mode calcium concentration in cancellous bone (Z-score - 1.7) and an increased percentage of highly mineralized cortical bone area (Z-score + 2.4) compared to reference. OLS characteristics showed several differences compared to reference data; among them, there were the highly increased OLS-porosity, OLS-area, and OLS-perimeter on the external cortex (Z-scores + 6.8, + 4.4 and 5.4, respectively). Our findings suggest that increased bone formation reduced matrix mineralization in cancellous bone while the enhanced amount of primary bone in the external cortex increased the portion of highly mineralized cortical bone and caused OLS-characteristics abnormalities. Our results indicate further that remodeling of primary bone might be disturbed or delayed in agreement with the decreased number of osteoclasts observed in this child with Proteus syndrome.

Berlin Heart EXCOR® pediatric ventricular assist device in a patient with Sotos syndrome: a case report

Introduction

Berlin Heart EXCOR® pediatric ventricular assist device is a mechanical circulatory support device currently used in pediatric patients. Sotos syndrome is a well-described multiple anomaly syndrome characterized by overgrowth, distinctive craniofacial appearance, cardiac abnormalities, and variable learning disabilities.

Case presentation

We describe a 7-year-old female Caucasian child with classic Sotos syndrome features subjected to implantation of Berlin Heart EXCOR® pediatric biventricular assist device mechanical support. A heart transplant was carried out after a support time of 459 days. After 5 years of follow-up, our patient is clinically stable and the performance of the transplanted heart is excellent.

Conclusion

This case confirms that Berlin Heart EXCOR® pediatric ventricular assist device can provide satisfactory and safe circulatory support for children with end-stage heart diseases, even in those with Sotos syndrome. The syndrome is not a contraindication to implantation, since the complications are the same as those observed in patients without the syndrome and the prognosis is not affected by the disease.

Pseudoacromegaly

Individuals with acromegaloid physical appearance or tall stature may be referred to endocrinologists to exclude growth hormone (GH) excess. While some of these subjects could be healthy individuals with normal variants of growth or physical traits, others will have acromegaly or pituitary gigantism, which are, in general, straightforward diagnoses upon assessment of the GH/IGF-1 axis. However, some patients with physical features resembling acromegaly - usually affecting the face and extremities -, or gigantism - accelerated growth/tall stature - will have no abnormalities in the GH axis. This scenario is termed pseudoacromegaly, and its correct diagnosis can be challenging due to the rarity and variability of these conditions, as well as due to significant overlap in their characteristics. In this review we aim to provide a comprehensive overview of pseudoacromegaly conditions, highlighting their similarities and differences with acromegaly and pituitary gigantism, to aid physicians with the diagnosis of patients with pseudoacromegaly.

Histone Lysine Methylation and Neurodevelopmental Disorders

Methylation of several lysine residues of histones is a crucial mechanism for relatively long-term regulation of genomic activity. Recent molecular biological studies have demonstrated that the function of histone methylation is more diverse and complex than previously thought. Moreover, studies using newly available genomics techniques, such as exome sequencing, have identified an increasing number of histone lysine methylation-related genes as intellectual disability-associated genes, which highlights the importance of accurate control of histone methylation during neurogenesis. However, given the functional diversity and complexity of histone methylation within the cell, the study of the molecular basis of histone methylation-related neurodevelopmental disorders is currently still in its infancy. Here, we review the latest studies that revealed the pathological implications of alterations in histone methylation status in the context of various neurodevelopmental disorders and propose possible therapeutic application of epigenetic compounds regulating histone methylation status for the treatment of these diseases.

Novel roles of amyloid-beta precursor protein metabolites in fragile X syndrome and autism

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and is associated with up to 5% of autism cases. Several promising drugs are in preclinical testing for FXS; however, bench-to-bedside plans for the clinic are severely limited due to lack of validated biomarkers and outcome measures. Published work from our laboratories has demonstrated altered levels of amyloid-beta (Aβ) precursor protein (APP) and its metabolites in FXS and idiopathic autism. Westmark and colleagues have focused on β-secretase (amyloidogenic) processing and the accumulation of Aβ peptides in adult FXS models, whereas Lahiri and Sokol have studied α-secretase (non-amyloidogenic or anabolic) processing and altered levels of sAPPα and Aβ in pediatric autism and FXS. Thus, our groups have hypothesized a pivotal role for these Alzheimer's disease (AD)-related proteins in the neurodevelopmental disorders of FXS and autism. In this review, we discuss the contribution of APP metabolites to FXS and autism pathogenesis as well as the potential use of these metabolites as blood-based biomarkers and therapeutic targets. Our future focus is to identify key underlying mechanisms through which APP metabolites contribute to FXS and autism condition-to-disease pathology. Positive outcomes will support utilizing APP metabolites as blood-based biomarkers in clinical trials as well as testing drugs that modulate APP processing as potential disease therapeutics. Our studies to understand the role of APP metabolites in developmental conditions such as FXS and autism are a quantum leap for the neuroscience field, which has traditionally restricted any role of APP to AD and aging.

De novo nonsense and frameshift variants of TCF20 in individuals with intellectual disability and postnatal overgrowth

Recently, germline variants of the transcriptional co-regulator gene TCF20 have been implicated in the aetiology of autism spectrum disorders (ASD). However, the knowledge about the associated clinical picture remains fragmentary. In this study, two individuals with de novo TCF20 sequence variants were identified in a cohort of 313 individuals with intellectual disability of unknown aetiology, which was analysed by whole exome sequencing using a child-parent trio design. Both detected variants - one nonsense and one frameshift variant - were truncating. A comprehensive clinical characterisation of the patients yielded mild intellectual disability, postnatal tall stature and macrocephaly, obesity and muscular hypotonia as common clinical signs while ASD was only present in one proband. The present report begins to establish the clinical picture of individuals with de novo nonsense and frameshift variants of TCF20 which includes features such as proportionate overgrowth and muscular hypotonia. Furthermore, intellectual disability/developmental delay seems to be fully penetrant amongst known individuals with de novo nonsense and frameshift variants of TCF20, whereas ASD is shown to be incompletely penetrant. The transcriptional co-regulator gene TCF20 is hereby added to the growing number of genes implicated in the aetiology of both ASD and intellectual disability. Furthermore, such de novo variants of TCF20 may represent a novel differential diagnosis in the overgrowth syndrome spectrum.

Overgrowth Syndromes

Numerous multiple malformation syndromes associated with pathologic overgrowth have been described and, for many, their molecular bases elucidated. This review describes the characteristic features of these overgrowth syndromes, as well as the current understanding of their molecular bases, intellectual outcomes, and cancer predispositions. We review syndromes such as Sotos, Malan, Marshall-Smith, Weaver, Simpson-Golabi-Behmel, Perlman, Bannayan-Riley-Ruvalcaba, PI3K-related, Proteus, Beckwith-Wiedemann, fibrous dysplasia, Klippel-Trenaunay-Weber, and Maffucci.

Generalized overgrowth syndromes with prenatal onset

Children with generalized overgrowth syndromes are large at birth, or have excessive postnatal growth. Many of these syndromes are associated with an increase in neoplasia. Consideration of the possibility of overgrowth syndrome in a pediatric patient who presents with increased growth parameters, variable malformations and neurodevelopmental phenotype, and distinctive features, is important for medical management, reproductive counseling, and tumor surveillance for some of the disorders. This review describes the clinical features and surveillance recommendations for the common generalized overgrowth syndromes the pediatrician may encounter. It also provides a glimpse into advances of recent years in understanding the molecular mechanisms responsible for the disrupted growth regulation in these disorders.

Stereological study of the neuronal number and volume of 38 brain subdivisions of subjects diagnosed with autism reveals significant alterations restricted to the striatum, amygdala and cerebellum

Introduction

A total of 38 brain cytoarchitectonic subdivisions, representing subcortical and cortical structures, cerebellum, and brainstem, were examined in 4- to 60-year-old subjects diagnosed with autism and control subjects (a) to detect a global pattern of developmental abnormalities and (b) to establish whether the function of developmentally modified structures matches the behavioral alterations that are diagnostic for autism. The volume of cytoarchitectonic subdivisions, neuronal numerical density, and total number of neurons per region of interest were determined in 14 subjects with autism and 14 age-matched controls by using unbiased stereological methods.

Results

The study revealed that significant differences between the group of subjects with autism and control groups are limited to a few brain regions, including the cerebellum and some striatum and amygdala subdivisions. In the group of individuals with autism, the total number and numerical density of Purkinje cells in the cerebellum were reduced by 25% and 24%, respectively. In the amygdala, significant reduction of neuronal density was limited to the lateral nucleus (by 12%). Another sign of the topographic selectivity of developmental alterations in the brain of individuals with autism was an increase in the volumes of the caudate nucleus and nucleus accumbens by 22% and 34%, respectively, and the reduced numerical density of neurons in the nucleus accumbens and putamen by 15% and 13%, respectively.

Conclusions

The observed pattern of developmental alterations in the cerebellum, amygdala and striatum is consistent with the results of magnetic resonance imaging studies and their clinical correlations, and of some morphometric studies that indicate that detected abnormalities may contribute to the social and communication deficits, and repetitive and stereotypical behaviors observed in individuals with autism.

Ezh2 regulates adult hippocampal neurogenesis and memory

Adult neurogenesis is thought to be crucial for preserving cognitive functions, which is tightly controlled by various epigenetic regulators. As the methyltransferase of histone H3K27, the role of Ezh2 in neurogenesis of adult mice and its mechanism of action are largely unknown. Here, we show that Ezh2 is expressed in actively dividing neural stem cells (NSCs)/progenitor cells as well as mature neurons, but not in quiescent NSCs in the subgranular zone. The deletion of Ezh2 in NSCs/progenitor cells results in a reduction in progenitor cell proliferation. Furthermore, we found that Ezh2 regulates progenitor cell proliferation by suppressing Pten expression and promoting the activation of Akt-mTOR. Moreover, the loss of Ezh2 in progenitor cells leads to a decrease in the number of neurons, which was observed by long-term tracing. Strikingly, conditional knockout of Ezh2 ultimately results in impairments in spatial learning and memory, contextual fear memory, and pattern separation. Our findings demonstrate the essential role of Ezh2 in the proliferation of progenitor cells, thus providing insight into the molecular mechanisms of adult neurogenesis in preserving cognitive functions.

Compared to what? Early brain overgrowth in autism and the perils of population norms

BACKGROUND

Early brain overgrowth (EBO) in autism spectrum disorder (ASD) is among the best replicated biological associations in psychiatry. Most positive reports have compared head circumference (HC) in ASD (an excellent proxy for early brain size) with well-known reference norms. We sought to reappraise evidence for the EBO hypothesis given 1) the recent proliferation of longitudinal HC studies in ASD, and 2) emerging reports that several of the reference norms used to define EBO in ASD may be biased toward detecting HC overgrowth in contemporary samples of healthy children.

METHODS

Systematic review of all published HC studies in children with ASD. Comparison of 330 longitudinally gathered HC measures between birth and 18 months from male children with autism (n = 35) and typically developing control subjects (n = 22).

RESULTS

In systematic review, comparisons with locally recruited control subjects were significantly less likely to identify EBO in ASD than norm-based studies (p < .001). Through systematic review and analysis of new data, we replicate seminal reports of EBO in ASD relative to classical HC norms but show that this overgrowth relative to norms is mimicked by patterns of HC growth age in a large contemporary community-based sample of US children (n ~ 75,000). Controlling for known HC norm biases leaves inconsistent support for a subtle, later emerging and subgroup specific pattern of EBO in clinically ascertained ASD versus community control subjects.

CONCLUSIONS

The best-replicated aspects of EBO reflect generalizable HC norm biases rather than disease-specific biomarkers. The potential HC norm biases we detail are not specific to ASD research but apply throughout clinical and academic medicine.

Autism spectrum disorders: the quest for genetic syndromes

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disabilities with various etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of ASD remains unclear. A number of genetic syndromes manifest ASD at higher than expected frequencies compared to the general population. These syndromes account for more than 10% of all ASD cases and include tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Williams, Duchenne, etc. Clinicians are increasingly required to recognize genetic disorders in individuals with ASD, in terms of providing proper care and prognosis to the patient, as well as genetic counseling to the family. Vice versa, it is equally essential to identify ASD in patients with genetic syndromes, in order to ensure correct management and appropriate educational placement. During investigation of genetic syndromes, a number of issues emerge: impact of intellectual disability in ASD diagnoses, identification of autistic subphenotypes and differences from idiopathic autism, validity of assessment tools designed for idiopathic autism, possible mechanisms for the association with ASD, etc. Findings from the study of genetic syndromes are incorporated into the ongoing research on autism etiology and pathogenesis; different syndromes converge upon common biological backgrounds (such as disrupted molecular pathways and brain circuitries), which probably account for their comorbidity with autism. This review paper critically examines the prevalence and characteristics of the main genetic syndromes, as well as the possible mechanisms for their association with ASD.

From neural development to cognition: unexpected roles for chromatin

Recent genome-sequencing studies in human neurodevelopmental and psychiatric disorders have uncovered mutations in many chromatin regulators. These human genetic studies, along with studies in model organisms, are providing insight into chromatin regulatory mechanisms in neural development and how alterations to these mechanisms can cause cognitive deficits, such as intellectual disability. We discuss several implicated chromatin regulators, including BAF (also known as SWI/SNF) and CHD8 chromatin remodellers, HDAC4 and the Polycomb component EZH2. Interestingly, mutations in EZH2 and certain BAF complex components have roles in both neurodevelopmental disorders and cancer, and overlapping point mutations are suggesting functionally important residues and domains. We speculate on the contribution of these similar mutations to disparate disorders.

Cognitive characteristics of PTEN hamartoma tumor syndromes

PURPOSE

We sought to characterize cognition in individuals with germline PTEN mutations (n = 23) as well as in PTEN mutation-negative individuals with classic Cowden syndrome or Bannayan-Riley-Ruvalcaba syndrome (n = 2).

METHODS

Twenty-five individuals completed a comprehensive neuropsychological evaluation. One sample t-tests and effect sizes were used to examine differences in participant test scores compared with normal controls. Composite scores were created for each patient within each of the cognitive domains assessed and classified as above average, average, or below average according to normative standards. χ(2) analyses compared these classifications to expected proportions in normal control samples.

RESULTS

The mean intelligence quotient was in the average range, and the range of intellectual functioning was very wide (from extremely low to very superior). However, in a large subset of patients, scores were lower than expected on measures of motor functioning, executive functioning, and memory recall, suggesting disruption of frontal circuits in these participants.

CONCLUSION

This is the first study to characterize cognition in individuals with PTEN mutations and associated syndromes using a comprehensive neuropsychological battery. Contrary to previous reports suggesting an association with intellectual disability, the mean intelligence quotient was average, and there was a broad range of intellectual abilities. Specific evidence of disruption of frontal circuits may have implications for treatment compliance and cancer surveillance, and further investigation is warranted.

Macrocephaly as a clinical indicator of genetic subtypes in autism

An association between autism and macrocephaly has been previously described. A subset of cases with extreme macrocephaly (>3 standard deviation [SD], 99.7th percentile) have been correlated to mutations in the gene phosphatase and tensin homolog (PTEN). However, the phenotypic and genetic characterization of the remaining cases remains unclear. We report the phenotypic classification and genetic testing evaluation of a cohort of 33 patients with autism and macrocephaly. Within our cohort, we confirm the association of PTEN mutations and extreme macrocephaly (>3 SD, 99.7th percentile) and identify mutations in 22% of cases, including three novel PTEN mutations. In addition, we define three phenotypic subgroups: (a) those cases associated with somatic overgrowth, (b) those with disproportionate macrocephaly, and (c) those with relative macrocephaly. We have devised a novel way to segregate patients into these subgroups that will aide in the stratification of autism macrocephaly cases. Within these subgroups, we further expand the genetic etiologies for autism cases with macrocephaly by describing two novel suspected pathogenic copy number variants located at 6q23.2 and 10q24.32. These findings demonstrate the phenotypic heterogeneity of autism cases associated with macrocephaly and their genetic etiologies. The clinical yield from PTEN mutation analysis is 22% and 9% from chromosomal microarray (CMA) testing within this cohort. The identification of three distinct phenotypic subgroups within macrocephaly autism patients may allow for the identification of their respective distinct genetic etiologies that to date have remained elusive.

The first neurosurgical analysis of 8 korean children with sotos syndrome

OBJECTIVE

Sotos Syndrome is characterized by macrocephaly, overgrowth, and developmental delay, and more than 300 patients have been reported worldwide to date. The authors reviewed the clinical characteristics of 8 patients with Sotos Syndrome in Korea for a new understanding and treatment strategies.

METHODS

The medical records of a total of eight Korean children with Sotos Syndrome were reviewed. All patients underwent developmental checkup, lumbar punctures for measurement of intracranial pressure (ICP), brain and spine magnetic resonance imaging and computerized tomography.

RESULTS

All 8 patients showed macrocephaly and the characteristic craniofacial features of Sotos Syndrome. Other clinical characteristics shown were overgrowth (7/8), developmental delay (7/8), congenital heart defect (3/8), flat foot (8/8), scoliosis (4/8), spina bifida (8/8), hydrocephalus (4/8), cavum vergae (3/8), and increased subdural fluid collection (5/8). Mean ICP measured via lumbar puncture was 27.35+/-6.25 cm H(2)O (range 20 to 36 cm H(2)O). Two patients received ventriculo-peritoneal shunt, and 1 patient underwent subduro-peritoneal shunt with improvement. Spinal orthosis was applied to 4/5 patients with scoliosis and 4/8 children with flat foot were provided with foot orthosis.

CONCLUSION

In this first Korean study of 8 Sotos Syndrome patients we demonstrated the presence of spina bifida and increased ICP, which had not been previously described. The authors therefore suggest that all patients with Sotos Syndrome should undergo examination for the presence of spina bifida, and that shunt procedures would improve development and alleviate clinical symptoms.

Genetic disorders associated with macrocephaly

Macrocephaly is associated with many genetic disorders and is a frequent cause of referral to the clinical geneticist. In this review we classify the commonly encountered macrocephaly disorders into useful categories and summarize recent genetic advances. Conditions where macrocephaly is a predominant aspect of the clinical presentation are discussed and a diagnostic approach to the common macrocephaly disorders is provided. Some emphasis is placed on familial macrocephaly (sometimes referred to as benign external hydrocephalus) and on the macrocephaly associated with autism spectrum disorders. The more recent conditions associated with the leukodystrophies and the organic acidurias are reviewed, but the well known conditions involving storage disorders and bone dysplasias are mentioned but not discussed. The genetic macrocephaly conditions cover a broad spectrum of gene disorders and their related proteins have diverse biological functions. As of yet it is not clear what precise biological pathways lead to generalized brain overgrowth.

Sotos syndrome

Sotos syndrome is an overgrowth condition characterized by cardinal features including excessive growth during childhood, macrocephaly, distinctive facial gestalt and various degrees of learning difficulty, and associated with variable minor features. The exact prevalence remains unknown but hundreds of cases have been reported. The diagnosis is usually suspected after birth because of excessive height and occipitofrontal circumference (OFC), advanced bone age, neonatal complications including hypotonia and feeding difficulties, and facial gestalt. Other inconstant clinical abnormalities include scoliosis, cardiac and genitourinary anomalies, seizures and brisk deep tendon reflexes. Variable delays in cognitive and motor development are also observed. The syndrome may also be associated with an increased risk of tumors. Mutations and deletions of the NSD1 gene (located at chromosome 5q35 and coding for a histone methyltransferase implicated in transcriptional regulation) are responsible for more than 75% of cases. FISH analysis, MLPA or multiplex quantitative PCR allow the detection of total/partial NSD1 deletions, and direct sequencing allows detection of NSD1 mutations. The large majority of NSD1 abnormalities occur de novo and there are very few familial cases. Although most cases are sporadic, several reports of autosomal dominant inheritance have been described. Germline mosaicism has never been reported and the recurrence risk for normal parents is very low (<1%). The main differential diagnoses are Weaver syndrome, Beckwith-Wiedeman syndrome, Fragile X syndrome, Simpson-Golabi-Behmel syndrome and 22qter deletion syndrome. Management is multidisciplinary. During the neonatal period, therapies are mostly symptomatic, including phototherapy in case of jaundice, treatment of the feeding difficulties and gastroesophageal reflux, and detection and treatment of hypoglycemia. General pediatric follow-up is important during the first years of life to allow detection and management of clinical complications such as scoliosis and febrile seizures. An adequate psychological and educational program with speech therapy and motor stimulation plays an important role in the global development of the patients. Final body height is difficult to predict but growth tends to normalize after puberty.

The phakomatoses: dermatologic clues to neurologic anomalies

The phakomatoses of particular interest to neurologists including Sturge-Weber syndrome, neurofibromatosis type 1, neurofibromatosis type 2, Bannayan-Riley-Ruvalcaba syndrome, and Proteus syndrome are presented. The physical manifestations required for clinical diagnosis, the neurologic features, and recommendations for management are given. The molecular etiology and genetic aspects of these disorders are briefly discussed as well as future implications of on-going research.

When is enlargement of the subarachnoid spaces not benign? A genetic perspective

Enlargement of the subarachnoid spaces is occasionally encountered during neuroimaging of children. This enlargement is generally regarded as a nonpathologic process that resolves uneventfully. However, there are several genetic disorders in which enlargement of the subarachnoid spaces can be an early sign, or the feature of an associated syndrome, that may aid in the underlying diagnosis. Recognizing subarachnoid space enlargement in these circumstances requires an understanding of the normal physiology of the subarachnoid space at different time points in a child's neurodevelopment. This article reviews the events shaping the subarachnoid space, both during normal physiologic maturation and in specific genetic disorders.

A case of Sotos syndrome with subduroperitoneal shunt

The authors present a case of Sotos syndrome with increasing severity of subdural hygroma from the age of 5 months, which was managed with a subduroperitoneal shunt at 10 months of age. The patient had been followed up until 30 months of age with continuing improvement of symptoms. The patient initially presented with dolichocephaly accompanied by macrocrania, early tooth development, repeated pneumonia infections and developmental retardation concerning crawling, sitting, walking and speaking at 5 months of age. Magnetic resonance imaging (MRI) demonstrated partial hypoplasia of the corpus callosum and bifrontal subdural hygroma. The patient underwent subduroperitoneal shunting at 10 months of age with partial improvement of symptoms. At 18 months of age, the patient showed increased irritability and sweating, and development of spinal kyphosis, which resulted from shunt malfunction as shown in the shuntogram. The appearance of cervical syringomyelia was also seen in the MRI. After shunt revision, the irritability, sweating and kyphosis improved along with disappearance of the syringomyelia. The authors describe a case of Sotos syndrome with subduroperitoneal shunt that showed syringomyelia which developed with shunt malfunction but disappeared after shunt revision. We emphasize the importance of active management such as subduroperitoneal shunting to drain the cerebrospinal fluid in the Sotos syndrome.

Macrocephaly and the control of brain growth in autistic disorders

Autism is a childhood-onset neuropsychiatric disorder characterized by marked impairments in social interactions and communication, with restricted stereotypic and repetitive patterns of behavior, interests, and activities. Genetic epidemiology studies indicate that a strong genetic component exists to this disease, but these same studies also implicate significant environmental influence. The disorder also displays symptomatologic heterogeneity, with broad individual differences and severity on a graded continuum. In the search for phenotypes to resolve heterogeneity and better grasp autism's underlying biology, investigators have noted a statistical overrepresentation of macrocephaly, an indicator of enlarged brain volume. This feature is one of the most widely replicated biological findings in autism. What then does brain enlargement signify? One hypothesis invoked for the origin of macrocephaly is a reduction in neuronal pruning and consolidation of synapses during development resulting in an overabundance of neurites. An increase in generation of cells is an additional mechanism for macrocephaly, though it is less frequently discussed in the literature. Here, we review neurodevelopmental mechanisms regulating brain growth and highlight one underconsidered potential causal mechanism for autism and macrocephaly--an increase in neurogenesis and/or gliogenesis. We review factors known to control these processes with an emphasis on nuclear receptor activation as one signaling control that may be abnormal and contribute to increased brain volume in autistic disorders.

Clinical and histopathological findings in Bannayan-Riley-Ruvalcaba syndrome

Bannayan-Riley-Ruvalcaba syndrome is a rare autosomal dominant genodermatosis with the classical triad of macrocephaly, genital lentiginosis, and intestinal polyposis. Characteristic mucocutaneous manifestations include vascular malformations, lipomatosis, speckled lentiginosis of the penis or vulva, facial verrucae-like or acanthosis nigricans-like lesions, and multiple acrochordons of the neck, axilla, and groin. We present a case of Bannayan-Riley-Ruvalcaba syndrome with macrocephaly, abnormal facies, lipoma, tender and painful arteriovenous hemangiomas, lymphangiokeratomas, musculoskeletal abnormalities, and localized myopathy. We also describe previously unreported findings, including peripheral neuropathy, punctate cystic changes in acral tubular bones, and enostosis of talus. Bannayan-Riley-Ruvalcaba syndrome needs recognition by dermatologists because affected patients may present with mucocutaneous and subcutaneous lesions that may simulate other dermatological disorders.

[The skin as an expression of neurological alterations in the neonate]

The skin is involved in many different genetic syndromes and diseases with multiple organ involvement. Neurodevelopmental disorders appear in many of these entities and knowledge of these cutaneous alterations may provide clues to their diagnosis. Recognizing these skin disorders in the newborn allows early identification of neonates with a biological risk of epilepsy and motor and/or cognitive disorders and enables them to be followed up. This helps to plan the management of these patients and, in many entities, to predict their natural history and provide genetic counseling to the family. This review examines the cutaneous signs that may provide important clues in the neonate that help to identify entities that carry a risk of neurodevelopmental disorders in the neonate.

Brain overgrowth in autism during a critical time in development: implications for frontal pyramidal neuron and interneuron development and connectivity

While abnormalities in head circumference in autism have been observed for decades, it is only recently that scientists have begun to focus in on the developmental origins of such a phenomenon. In this article we review past and present literature on abnormalities in head circumference, as well as recent developmental MRI studies of brain growth in this disorder. We hypothesize that brain growth abnormalities are greatest in frontal lobes, particularly affecting large neurons such as pyramidal cells, and speculate how this abnormality might affect neurofunctional circuitry in autism. The relationship to clinical characteristics and other disorders of macrencephaly are discussed.

Genetics of Sotos syndrome

PURPOSE OF REVIEW

Sotos syndrome (SoS) (OMIM #117550) is a childhood overgrowth syndrome characterized by excessive growth, distinctive craniofacial features, developmental delay, and advanced bone age. Recently, haploinsufficiency of the NSD1 gene has been identified as the major cause of SoS, with intragenic mutations or submicroscopic microdeletions being found in about 60 to 75% of clinically diagnosed patients with SoS.

RECENT FINDINGS

Recent reports provided much information about the genetic background of SoS, the NSD gene family, and genotype-phenotype correlation. They also added new perspectives in the discussion about a possible association between SoS and neoplasia.

SUMMARY

This review focuses on recent genetic developments in SoS. Clinical features and associated anomalies are reviewed in relation to possible functional roles of NSD1. Genotype-phenotype correlation between patients with SoS harboring either intragenic mutations or microdeletions is discussed as well as their implication for possible revision of the diagnostic criteria of SoS. Furthermore, future prospects in genetic research of SoS are presented.

Assessment of fetal intracranial pathologies first demonstrated late in pregnancy: cell proliferation disorders

A considerable number of central nervous system pathologies remain undiagnosed during the first two trimesters of pregnancy. This group of disorders includes anomalies of brain proliferation, migration and cortical organization. Due to the fact that a detailed ultrasound examination of the fetal brain is usually not performed during the third trimester the diagnosis of these disorders is usually only made in families with a previously affected child or in many cases be mere chance. In this article we review the feasibility of prenatal diagnosis of disorders of brain proliferation: microcephaly, macrocephaly, hemimegalencephaly and neoplastic and non-neoplastic abnormal cell types. We discuss the differential diagnosis and offer a stepwise approach to the diagnosis of the more common disorders.