A comprehensive and critical assessment of overgrowth and overgrowth syndromes

Glucose Homeostasis in Newborns: An Endocrinology Perspective

Physiologic adaptations in the postnatal period, along with gradual establishment of enteral feeding, help maintain plasma glucose concentrations in the neonatal period. The definition of normal plasma glucose in the neonatal period has been a subject of debate because of a lack of evidence linking a set plasma or blood glucose concentration to clinical symptoms or predictors of short- and long-term outcomes. However, there is consensus that maintaining plasma glucose in the normal range for age is important to prevent immediate and long-term neurodevelopmental consequences of hypoglycemia or hyperglycemia. The specific management strategy for abnormal glucose levels in neonates depends on the underlying etiology, and interventions could include nutritional changes, medications, hormone therapy, or even surgery. Here, we will review the physiological processes that help maintain plasma glucose in newborns and discuss the approach to a newborn with disordered glucose homeostasis, with an emphasis on the endocrine basis of abnormal glucose homeostasis.

X-linked duplication copy number variation in a familial overgrowth condition

We describe an overgrowth condition associated with X-linked copy number variation. Three brothers displayed an overgrowth pattern at birth that continued postnatally. Clinical findings included macrocephaly, distinctive facial features, developmental delay and variable clubfoot. Normal fetal growth was noted until the third trimester by Hadlock standards, revealing a late gestational overgrowth pattern. Microarray analysis in the family showed a maternally inherited 680 kb copy number duplication at Xq26.1-q26.2 in all three brothers. Molecular sequencing for known overgrowth conditions including GPC3, Sotos 1 (NSD1), Malan (NFIX), Perlman (DIS3L2), Weaver (EZH2), Opitz-Kaveggia (MED12) loci were negative. BWS IC1 and IC2 methylation and CDKN1C testing was also negative. Normal IGF1 levels excluded X-linked acrogiantism. The duplicated region Xq26.1-q26.2 contained IGSF1 and at least part of the lncRNA FIRRE. IGSF1, a highly expressed pituitary immunoglobulin superfamily gene, was recently implicated in a genome-wide association study of canine size. IGSF1 variants were associated with large canine breeds compared to smaller breeds. Our findings support the hypothesis that an X-linked variant encompassing the IGSF1 region may be associated with body size. Although IGSF1 loss has been noted in human hypothyroidism, this is the first reported phenotype in a family with copy number duplication in the region. Our findings suggest that prenatal evaluation, cross-species evaluation, Mendelian, and GWAS studies may describe a distinctive familial condition and its corresponding phenotypic features.

Fifteen-minute consultation: Assessment, surveillance and management of hemihypertrophy

This article aims to provide a structured and concise guide for the general paediatrician managing a child with hemihypertrophy. Hemihypertrophy is a relatively uncommon condition. The significance is that a proportion of those affected are at risk of developing malignancies in childhood. For these children regular surveillance is required. We have outlined how one might assess and investigate a child presenting with hemihypertrophy. We have also formulated a practicable surveillance strategy which is in line with the current Royal College of Paediatrics and Child Health (RCPCH) guideline 'Wilms' tumour surveillance in at-risk children'.

Total Hemi-overgrowth in Pigmentary Mosaicism of the (Hypomelanosis of) Ito Type: Eight Case Reports

Pigmentary mosaicism of the (hypomelanosis of) Ito type is an umbrella term, which includes phenotypes characterized by mosaic hypopigmentation in the form of streaks, whorls, patchy, or more bizarre skin configurations (running along the lines of Blaschko): these cutaneous patterns can manifest as an isolated skin disorder (pigmentary mosaicism of the Ito type) or as a complex malformation syndrome in association with extracutaneous anomalies (most often of the musculoskeletal and/or nervous systems) (hypomelanosis of Ito). Affected individuals are anecdotally reported to have also partial or total body hemi-overgrowth (HOG), which often causes moderate to severe complications.We studied the occurrence and features of HOG in the 114 children and adults with mosaic pigmentary disorders of the Ito type diagnosed and followed up (from 2 to 22 years; average follow-up 16 years) at our Institutions.Eight patients (5 M, 3 F; aged 4 to 25 years; median age 16 years) out of the 114 analyzed (7%) fulfilled the criteria for unilateral HOG, with differences in diameter ranging from 0.4 to 4.0 cm (upper limbs) and 1.0 to 9.0 cm (lower limbs). Moreover, among these 8 patients, 5/8 filled in the 75th to 90th percentile for height; 6/8 had associated kyphoscoliosis; and 5/8 showed cognitive delays. No tumour complications were recorded. Overall, 6/8 HOG patients presented with additional (extracutaneous) syndromic manifestations, apart from the HOG (ie, with a clinical phenotype of hypomelanosis of Ito).The present study, which includes children and adults with the longest follow-up so far recorded, confirms the association between pigmentary mosaicism of the Ito type and HOG lowering previous estimates (7% vs 16%) for HOG in the context of mosaic hypopigmentation. A careful examination, looking at subtle to moderate asymmetries and associated complications within the spectrum of these mosaic pigmentary disorders, is recommended.

Renal agenesis in a child with ipsilateral hemihypertrophy

Hemihypertrophy is a clinical condition defined as an asymmetric enlargement of one side of the body. Inguinal hernias, renal cysts, cryptorchidism, ectasias of collecting tubes, medullary sponge kidney and horse-shoe kidney are examples of abnormalities associated with hemihypertrophy that have been described in the literature. We report here a 17.2-year-old patient with a left hemihypertrophy and renal agenesis with contralateral right compensatory renal hypertrophy together with normal renal function and blood pressure in the absence of proteinuria. He also presented with faint macular hyperpigmented skin lesions on his left upper arm, forehead and abdomen. To the best of our knowledge, this is the first report of renal agenesis and hemihypertrophy in the same patient. Hemihypertrophy can be seen as a component of Klippel-Trenaunay-Weber syndrome. The other components of this syndrome are varicose veins, skin naevus and arteriovenous malformations. Although renal agenesis, hemihypertrophy and hyperpigmented macular skin lesions (skin naevuses) may be incidental findings, together they may form a variant of Klippel-Trenaunay-Weber syndrome, as in our case.

Weaver syndrome and neuroblastoma

Overgrowth syndromes such as Beckwith-Wiedemann syndrome, Sotos syndrome, and Weaver syndrome have an increased risk of neoplasia. Two previous cases of neuroblastoma have been reported in children with Weaver syndrome. We present a third description of a patient with Weaver syndrome and neuroblastoma. In a child with phenotypic characteristics consistent with Weaver syndrome, evaluation for neuroblastoma should be considered.

Constitutional UPD for chromosome 11p15 in individuals with isolated hemihyperplasia is associated with high tumor risk and occurs following assisted reproductive technologies

Isolated hemihyperplasia (IH) refers to a distinct diagnosis involving asymmetric overgrowth of single or multiple organs or regions of the body and can result from various genomic changes including molecular alterations of 11p15; these are paternal uniparental disomy (UPD), and alterations of methylation at two imprinting centers at 11p15: IC1 (H19) and IC2 (KCNQ1OT1). As little information is available on the molecular basis of tumor development in IH, or on the frequency of tumors in children with different molecular subtypes of IH, molecular testing was undertaken on 51 patients with IH and revealed: 8 (16%) with UPD, 3 (6%) with hypomethylation at KCNQ1OT1, and 0 with hypermethylation at H19. Of the 8 patients with UPD, 4 had tumors (3 hepatoblastomas, 1 Wilms tumor); 0/3 patients with hypomethylation at KCNQ1OT1 had a tumor; of the remaining 40 with no molecular alterations, 6 had tumors (3 Wilms tumors, 2 neuroblastomas, 1 adrenocortical adenoma). The 50% tumor frequency in patients with IH and UPD was statistically significantly higher than the 15% tumor frequency in those with IH and no molecular alteration detected (Fisher's exact test P = 0.047, OR 5.67). This is the first demonstration that UPD at 11p15 in patients with IH confers a higher tumor risk than in patients with IH without this molecular change. Of note, two of the eight patients with UPD and IH were conceived using assisted reproductive technologies (ART), thus raising the question whether ART might impact the rate of somatic recombination during embryonic development.

Risk of tumorigenesis in overgrowth syndromes: a comprehensive review

Overgrowth syndromes (OGS) comprise a heterogeneous group of disorders in which the main characteristic is that either weight, height, or head circumference is 2-3 standard deviations (SD) above the mean for sex and age. A striking feature of OGS is the risk of neoplasms. Here, the relative frequency of specific tumors in each OGS, topographic location, and age of appearance is determined by reviewing published cases. In some OGS (Perlman, Beckwith-Wiedemann, and Simpson-Golabi-Behmel syndromes and hemihyperplasia) more than 94% of tumors appeared in the abdomen usually before 10 years of age, mainly embryonal in type. In Perlman syndrome, only Wilms tumor has been recorded, whereas in Sotos syndrome, lympho-hematologic tumors are most frequent. Based on literature review, a specific schedule protocol for tumor screening is suggested for each OGS. A schedule with different intervals and specific tests is proposed for a more rational cost/benefit program for these disorders.

Nevo syndrome is allelic to the kyphoscoliotic type of the Ehlers-Danlos syndrome (EDS VIA)

We report on seven patients affected with Nevo syndrome, a rare, autosomal recessive disorder characterized by increased perinatal length, kyphosis, muscular hypotonia, and joint laxity. Since its first description by Nevo et al. [1974], only a few cases have been reported. Because some of these patients present clinical features similar to those of the kyphoscoliotic type of Ehlers-Danlos syndrome (EDS VIA), an inherited connective tissue disorder characterized by a deficiency of lysyl hydroxylase due to mutations in PLOD1, we studied seven patients with Nevo syndrome, three of whom have previously been reported, and four of whom are new. In the five patients from whom urine was available, the ratio of total urinary lysyl pyridinoline (LP) to hydroxylysyl pyridinoline (HP) was elevated (8.2, 7.8, 8.6, 3.5, and 4.8, respectively) compared with that in controls (0.20 +/- 0.05, range 0.10-0.38), and similar to that observed in patients with EDS VIA (5.97 +/- 0.99, range 4.3-8.1). Six patients were homozygous for a point mutation in exon 9 of PLOD1 causing a p.R319X nonsense mutation, while one patient was homozygous for a large deletion comprising exon 17 of PLOD1. We conclude that the Nevo syndrome is allelic to and clinically indistinguishable from EDS VIA, and present evidence that increased length at birth and wristdrop, in addition to muscular hypotonia and kyphoscoliosis, should prompt the physician to consider EDS VIA earlier than heretofore.

Beckwith-Wiedemann syndrome: historical, clinicopathological, and etiopathogenetic perspectives

Macroglossia, prenatal or postnatal overgrowth, and abdominal wall defects (omphalocele, umbilical hernia, or diastasis recti) permit early recognition of Beckwith-Wiedemann syndrome. Complications include neonatal hypoglycemia and an increased risk for Wilms tumor, adrenal cortical carcinoma, hepatoblastoma, rhabdomyosarcoma, and neuroblastoma, among others. Perinatal mortality can result from complications of prematurity, pronounced macroglossia, and rarely cardiomyopathy. The molecular basis of Beckwith-Wiedemann syndrome is complex, involving deregulation of imprinted genes found in 2 domains within the 11p15 region: telomeric Domain 1 (IGF2 and H19) and centromeric Domain 2 (KCNQ1, KCNQ1OT1, and CDKN1C). Topics discussed in this article are organized as a series of perspectives: general, historical, epidemiologic, clinical, pathologic, genetic/molecular, diagnostic, and differential diagnostic.

Macrocephaly-cutis marmorata telangiectatica congenita: report of six new patients and a review

We report on six additional patients with macrocephaly-cutis marmorata telangiectatica congenita (M-CMTC; MIM 602501) and review the literature. This syndrome is a multiple congenital anomalies/mental retardation and overgrowth disorder comprising macrocephaly, cutis marmorata, vascular marks of lip and/or philtrum, syndactyly, hemihypertrophy, CNS anomalies, and developmental delay. Based on the findings in our 6 patients and on 69 patients previously reported we listed the very frequent (observed in >75%), frequent (25-75%), and less frequent (>25%) components of the syndrome.

Non-syndromic hemihyperplasia in a male and his mother

We present two family members with non-syndromic hemihyperplasia (HHP), which developed in adolescence. We have reviewed reported familial cases of HHP and conclude that presentation is similar to sporadi cases and that all affected family members have been related through a maternal relative.

Beckwith-Wiedemann syndrome and isolated hemihyperplasia

CONTEXT

Beckwith-Wiedemann syndrome is a complex and heterogeneous overgrowth syndrome with genetic and epigenetic alterations, involving genomic imprinting and cancer predisposition. Isolated hemihyperplasia is of unknown cause, and it may represent a partial or incomplete expression of Beckwith-Wiedemann syndrome.

OBJECTIVES

A clinical and molecular review and proposal of the use of an experimental protocol to provide a practical approach for the physician.

DATA SYNTHESIS

This review demonstrates the genetic and epigenetic mechanisms involved in the Beckwith-Wiedemann syndrome and isolated hemihyperplasia, and the candidate genes. To our knowledge, this is the first Brazilian protocol for research into these disorders. The results have been used at the Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, to elucidate the basis of Beckwith-Wiedemann syndrome and isolated hemihyperplasia, and have been applied at the Hospital Universitário of the Faculdade de Medicina.

CONCLUSIONS

Elucidation of the etiological mechanisms and use of a laboratory protocol to detect alterations in these disorders may be useful for guiding the management of such patients and genetic counseling of the families.

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

Mental deficiency, alterations in performance, and central nervous system (CNS) abnormalities are discussed in the following overgrowth syndromes: Sotos syndrome, Weaver syndrome, Proteus syndrome, neurofibromatosis type 1, fragile X syndrome, syndromes with neonatal hypoglycemia, Simpson-Golabi-Behmel syndrome, hemihyperplasia, Sturge-Weber syndrome, Bannayan-Riley-Ruvalcaba/Cowden syndrome, macrocephaly-autism syndrome, PEHO syndrome, chromosomal syndromes, and other miscellaneous syndromes.

Teratogenesis of holoprosencephaly

Teratogenic causes of holoprosencephaly are critically assessed. A brief general review of holoprosencephaly is followed by four tables summarizing etiologic factors. Subjects evaluated here include: 1) maternal diabetes; 2) ethyl alcohol; 3) retinoic acid; 4) mutated genes and teratogens involving the sonic hedgehog signaling network and cholesterol biosynthesis; and 5) cholesterol trafficking, sterol adducts, target tissue response, and sterol sensing domain.

Asymmetry: molecular, biologic, embryopathic, and clinical perspectives

This overview of asymmetry addresses the following topics: chiral molecules; asymmetric signaling molecules, including N-cadherin, Shh, Fgf8, lefty1, lefty2, nodal, Pitx2, activin betaB, activin receptor IIA, and cSnR; situs abnormalities; asymmetric cell division; laterality in humans and animals; behavioral asymmetry in humans and animals; asymmetric embryopathies, including Tessier-type "clefts"; hemiasymmetries such as hemihyperplasia, hemihypoplasia, and hemiatrophy; asymmetric vascular syndromes, including Klippel-Trenaunay and Sturge-Weber syndromes; plagiocephaly of the synostotic and deformational types; somatic mosaicism, including a discussion of McCune-Albright syndrome, fibrous dysplasia, GNAS1 mutations, and Proteus syndrome.

Acid sphingomyelinase deficiency in Beckwith Wiedemann syndrome

We report the association of Beckwith-Wiedemann syndrome (BWS) and a residual acid sphingomyelinase (ASM) activity of about 35% in a 23 months old Hungarian boy. Besides the classical triad of exomphalos, macroglossia and gigantism some other BWS-related features: polyhydramnios (known from the praenatal history), hemihypertrophy, craniofacial dysmorphy, a mild mental retardation, bilaterally undescended testes, cardiac anomalies and a terminally developed, fatal embryonal rhabdomyosarcoma were present in the patient. The decreased activity of the ASM was measured in the patient s skin fibroblasts. This result, with hepatomegaly, mental retardation, feeding problems, a failure to thrive and muscle-hypotony, partially resembled the ASM-deficient forms of Niemann-Pick disease (NPD). Morphological analysis of the bone-marrow cells gave normal results. There was no chromosomal alteration found by conventional karyotyping of the patient s lymphocytes.BWS-associated genes as well as the human ASM gene (SMPD1) are all located at 11p15. DNA-studies by region specific markers as well as mutational analysis for the most common NPD-mutations are planned in the future. This is the first report on the simultaneous occurrence of BWS and ASM-deficiency.

Genetics of Beckwith-Wiedemann syndrome-associated tumors: common genetic pathways

A specific subset of solid childhood tumors-Wilms' tumor, adrenocortical carcinoma, rhabdomyosarcoma, and hepatoblastoma-is characterized by its association with Beckwith-Wiedemann syndrome. Genetic abnormalities found in these tumors affect the same chromosome region (11p15), which has been implicated in the etiology of Beckwith-Wiedemann syndrome. This suggests that the development of these tumors occurs along a common genetic pathway involving chromosome 11. To search for additional common genetic pathways, this article reviews the genetic data published for these tumors. It was found that, up until now, the only genetic abnormalities detected in all four tumors affect chromosome band 11p15 and the TP53 gene. In addition, there are several aberrations that occur in two or three of the neoplasms. It is concluded that, of the four tumors, the genetic relationship is most evident between Wilms' tumor and rhabdomyosarcoma.

Mechanisms of in utero overgrowth

Determination of the mechanisms that lead to in utero overgrowth has proved elusive. Recently, however, our knowledge has significantly expanded as a result of the generation of experimental mouse models, engineered to disrupt the expression of one or more genes (knockout mice), and by detailed molecular and genetic analyses of infants and children with overgrowth syndromes. Studies of knockout mice have largely defined the essential roles of the insulin-like growth factors (IGF-I and IGF-II), insulin and their receptors in embryonic and fetal growth, and have provided compelling evidence that increased IGF-II gene expression and/or abundance can stimulate excessive fetal somatic growth. The IGF-II gene is usually expressed only by the paternally derived allele; however, when this imprinting is erased and IGF-II expression is biallelic, fetal overgrowth ensues. Such increased IGF-II expression would appear to explain the overgrowth in Beckwith-Wiedemann syndrome. Using the information gathered from knockout mice as a guide to human studies, detailed genetic investigations are likely to unravel the mechanisms behind other human overgrowth syndromes.

Hemihypertrophy and a poorly differentiated embryonal rhabdomyosarcoma of the pelvis

BACKGROUND

Asymmetry of the limbs (conventionally known as hemihypertrophy) is one of the overgrowth syndromes occurring sporadically in the general population at a frequency of approximately 1:86,000. Hemihypertrophy is also reported as part of the Beckwith-Wiedemann syndrome which has as its cardinal features omphalocele, macroglossia and gigantism with hypoglycemia, organomegaly, renal anomalies, hemihypertrophy, and embryonal tumors occurring less frequently. Various neoplasms are also associated with isolated hemihypertrophy. Wilms tumor, adrenocortical carcinoma, and hepatoblastoma are the most frequent. Rhabdomyosarcoma, neuroblastoma, phaeochromocytoma, and undifferentiated sarcoma of the lung are encountered only rarely. Loss of heterozygosity (LOH) of chromosome 11p15.5 is strongly associated with childhood embryonal tumors, particularly Wilms tumor, hepatoblastoma, and rhabdomyosarcoma.

PROCEDURE AND RESULTS

In this article, we describe an adolescent male with congenital asymmetry of the lower limbs who presented with a large poorly differentiated pelvic sarcoma. Conventional histologic, immunohistochemical, and ultrastructural studies of this tumor were insufficient for accurate subclassfication. However, positive staining for MyoD1 (a recently identified embryonically expressed marker of muscle differentiation) and LOH at the tyrosine hydroxylase locus of chromosome 11p15.5 by molecular analysis favored the diagnosis of embryonal rhabdomyosarcoma over an undifferentiated sarcoma.

CONCLUSIONS

This case stresses the importance of pursuing clinical findings when they occur in conditions with an increased risk of developing cancer, which in this case was asymmetry of a limb. Also illustrated by this patient is the need for early consideration of molecular diagnostic tests where available, to refine an uncertain pathologic diagnosis that may ultimately have an impact on treatment and prognosis.

Clinical differentiation between Proteus syndrome and hemihyperplasia: description of a distinct form of hemihyperplasia

Proteus syndrome is a rare and highly variable hamartomatous syndrome that can affect multiple organ systems. It is characterized by hyperplastic lesions of connective tissue, vascular malformations, linear verrucous epidermal nevi, and hyperostoses. The cause of the disorder is unknown, but the current working hypothesis is that it is caused by a mosaic alteration that leads to a highly variable phenotype, equal sex ratio, sporadic occurrence, and discordant monozygotic twins. Herein we describe our experience with 18 patients with a referring diagnosis of Proteus syndrome. It was found that imaging studies are very useful for the characterization of the syndrome. One finding was that splenic hyperplasia can be a manifestation of Proteus syndrome. Analysis of the clinical data shows that Proteus syndrome is frequently confused with "hemihyperplasia." A distinct subtype of hemihyperplasia is defined that includes static or mildly progressive hemihyperplasia and multiple lipomata.

The syndromes of Sotos and Weaver: reports and review

The syndromes of Sotos and Weaver are paradigmatic of the daily nosologic difficulties faced by clinical geneticists attempting to diagnose and counsel, and to give accurate prognoses in cases of extensive phenotypic overlap between molecularly undefined entities. Vertebrate development is constrained into only very few final or common developmental paths; therefore, no developmental anomaly seen in humans is unique to ("pathognomonic" of) one syndrome. Thus, it is not surprising that prenatal overgrowth occurs in several syndromes, including the Sotos and Weaver syndromes. Are they sufficiently different in other respects to allow the postulation of locus (rather than allele) heterogeneity? Phenotypic data in both conditions are biased because of ascertainment of propositi, and the apparent differences between them may be entirely artificial as they were between the G and BBB syndromes. On the other hand, the Sotos syndrome may be a cancer syndrome, the Weaver syndrome not (though a neuroblastoma was reported in the latter); in the former there is also remarkably advanced dental maturation rarely commented on in the latter. In Weaver syndrome there are more conspicuous contractures and a facial appearance that experts find convincingly different from that of Sotos individuals. Nevertheless, the hypothesis of locus heterogeneity is testable; at the moment we are inclined to favor the hypothesis of allele heterogeneity. An international effort is required to map, isolate, and sequence the causal gene or genes.

Megalencephaly, mega corpus callosum, and complete lack of motor development: a previously undescribed syndrome

We report on 3 sporadic cases of in utero onset megalencephaly. Children were born to healthy nonconsanguineous parents after uneventful pregnancies. Head circumferences were just above the 97th centile at birth in 2 patients, 2 cm above the 97th centile in 1 patient, and subsequently increased to 4.5-6.5 cm above the 97th centile at age 5 years. All patients completely lacked motor and speech development and showed very little intellectual progress. There was a distinctive facial aspect with frontal bossing, low nose bridge, and large eyes, but no cutaneous abnormalities and no signs of other organ involvement. Magnetic resonance imaging showed bilateral megalencephaly with a broad corpus callosum, enlarged white matter, and focally thick gray matter, resulting in pachygyric appearance of the cortex. Opercularization was incomplete, and the Sylvian fissures were wide. Somatosensory evoked potentials in 1 patient showed normal latencies of cervical and contracortical potentials but bilaterally increased cortical amplitudes. To the best of our knowledge, no similar case observations have been recorded previously.

Multiple Sp1 sites efficiently drive transcription of the TATA-less promoter of the human glypican 3 (GPC3) gene

Simpson-Golabi-Behmel Syndrome (SGBS) is an X-linked disease characterized by pre- and postnatal overgrowth. Recently, we have shown that mutations in the glypican family gene, GPC3, cause SGBS. This gene is predominantly expressed in the same mesoderm-derived tissues that overgrow in its absence. To investigate the basis for promoter function, 3.3kb of GC-rich DNA 5' of the transcribed region were fused to a luciferase cDNA, transfected into Caco-2 and NT2 cells, and assayed for activity. Deletion analysis identified a 218-bp fragment upstream of the transcription start site that conferred more than 80% of maximal reporter gene activation. This fragment contains five putative Sp1 binding sites, three of which (centered at nt -14, -34, and -92) were active when assessed by DNaseI footprinting and gel shift/supershift assays. Additionally, Sp1 specifically transactivated transcription in Sp1-deficient Drosophila SL2 cells, demonstrating the functionality of Sp1 on the GPC3 promoter. A full-length promoter construct was also highly active in HeLa cells, which do not express endogenous GPC3. These results indicate that the GPC3 promoter is dependent on Sp1 for proper activation, but tissue-specific repression in non-expressing cells must involve either DNA that lies outside the region tested or auxiliary structural features of chromatin.

New overgrowth syndrome and FGFR3 dosage effect

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Insulin-like growth factor 2 and overgrowth: molecular biology and clinical implications

The insulin-like growth factors, IGF1 and IGF2, play a fundamental role in human fetal growth. Of the growth disorders that involve excessive growth, many could be attributable to overexpression of IGF2. Because one copy of the IGF2 gene is silenced by genomic imprinting, several different molecular errors can double the number of active copies of the IGF2 gene. Although not formally demonstrated, each of these errors is expected to double the level of IGF2 expression. The nature and severity of the overgrowth might be dependent on the number and location of cells that carry the molecular defect.

Risk of cancer during the first four years of life in children from The Beckwith-Wiedemann Syndrome Registry

To determine the incidence and relative risk (RR) of cancer in children with Beckwith-Wiedemann syndrome (BWS), children with BWS were followed up from birth until death, diagnosis of cancer, fourth birthday, or last day of follow-up. A total of 183 children with BWS were followed up for 482 person-years. The end points were incidence of cancer, RR of cancer, and RR associated with specific BWS phenotypic features. Thirteen children were identified with cancers before the fourth year of life in comparison with fewer than one cancer expected in this group on the basis of general population rates over the same period. The average annual incidence of cancer in the first 4 years of life was 0.027 cancer per person-year. The RR of Wilms tumor (RR = 816; 95% confidence interval [CI], 359-1156), neuroblastoma (RR = 197; 95% CI, 22-711), and hepatoblastoma (RR = 2280; 95% CI, 928-11,656) were statistically significant. Asymmetry of the limbs (hemihypertrophy) was the only clinical feature associated with an increased RR of cancer (RR = 4.6; 95% CI, 1.5-14.2). Given the high incidence of cancer in infancy and early childhood of patients with BWS, a prospective study is warranted to address the utility of screening for cancer.

Analysis of exon/intron structure and 400 kb of genomic sequence surrounding the 5'-promoter and 3'-terminal ends of the human glypican 3 (GPC3) gene

GPC3, the gene modified in the Simpson-Golabi-Behmel gigantism/overgrowth syndrome (SGBS), is shown to span more than 500 kb of genomic sequence, with the transcript beginning 197 bp 5' of the translational start site. The Xq26.1 region containing GPC3 as the only known gene has been extended to > 900 kb by sequence analysis of flanking BAC clones. Two GC isochores (40.6 and 42.6% GC) are observed at the 5' and 3' ends of the locus, with a large repertoire of repetitive sequences that includes an unusual cluster of four L1 elements > 92% identical over 2.8 kb. Eight exons, accounting for the full 2.4-kb GPC3 cDNA, have been sequenced along with neighboring intronic regions. PCR assays have been developed to amplify each exon and exon/intron junction sequence, to help discriminate instances of SGBS among individuals with overgrowth syndromes and to facilitate mutational analysis of lesions in the gene.

Translocations involving 4p16.3 in three families: deletion causing the Pitt-Rogers-Danks syndrome and duplication resulting in a new overgrowth syndrome

Three families are reported who have a translocation involving 4p16.3. Nine subjects are described with the clinical features of the Pitt-Rogers-Danks (PRD) syndrome confirming pre- and postnatal growth failure, microcephaly, severe mental retardation, seizures, and a distinctive facial appearance; a deletion of 4p16.3 was seen in all eight patients studied with fluorescence in situ hybridisation (FISH). Eleven subjects had a new syndrome with physical overgrowth, heavy facial features, and mild to moderate mental handicap; a duplication of the chromosome region 4p16.3 was found in the four subjects studied. It is suggested that the growth abnormalities in these two families may be explained by a dosage effect of the fibroblast growth factor receptor gene 3 (FGFR3), which is located at 4p16.3, that is, a single dose leads to growth failure and a triple dose to physical overgrowth. We describe the molecular mapping of the translocation breakpoint and define it to within locus D4S43.

Novel findings in a patient with Weaver or a Weaver-like syndrome

We report on a young male patient with an overgrowth syndrome, who had normal birth weight. He had a number of manifestations typical of the Weaver syndrome (WS), such as advanced bone age, peculiar craniofacial appearance, and camptodactyly. He also showed severe mental and speech retardation and demineralisation of the bones of the hands and feet. The latter can be considered as unreported manifestations of WS, or the patient could represent an example of a new WS-like syndrome.

Mutations in GPC3, a glypican gene, cause the Simpson-Golabi-Behmel overgrowth syndrome

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked condition characterized by pre- and postnatal overgrowth with visceral and skeletal anomalies. To identify the causative gene, breakpoints in two female patients with X;autosome translocations were identified. The breakpoints occur near the 5' and 3' ends of a gene, GPC3, that spans more than 500 kilobases in Xq26; in three families, different microdeletions encompassing exons cosegregate with SGBS. GPC3 encodes a putative extracellular proteoglycan, glypican 3, that is inferred to play an important role in growth control in embryonic mesodermal tissues in which it is selectively expressed. Initial western- and ligand-blotting experiments suggest that glypican 3 forms a complex with insulin-like growth factor 2 (IGF2), and might thereby modulate IGF2 action.

Femoral hypoplasia-unusual facies syndrome with bifid hallux, absent tibia, and macrophallus: a report of a Bedouin baby

A male Bedouin baby with the clinical profile of femoral hypoplasia-unusual facies syndrome is described. The phenotype includes bilateral asymmetrical lower limb hypoplasia/aplasia with short remnants of both femora, absent right tibia, bifid right big toe, dysmorphic facies, thoracic/pelvic abnormalities, macrophallus, and bilateral cryptorchidism. This report re-emphasises the previously described rare association of femoral hypoplasia-unusual facies syndrome with preaxial polydactyly and suggests that the clinical spectrum of the syndrome could be stretched further to accommodate other unusual traits, for example, macrophallus and absent tibia.

Clinical overlap of Beckwith-Wiedemann, Perlman and Simpson-Golabi-Behmel syndromes: a diagnostic pitfall

We report on a child who died in the neonatal period. Major external anomalies included foetal overgrowth, macroglossia, and ambiguous genitalia (micropenis and perineoscrotal hypospadias with cryptorchidism). Necropsy showed a large right diaphragmatic hernia, visceromegaly, multicystic kidney dysplasia, Langerhans islet hyperplasia, nephroblastomatosis, multiple adrenal adenomas, and dysplastic testicles. The child illustrates the difficulties of the differential diagnosis of overgrowth syndromes in the neonatal period, and the phenotypic overlap of Beckwith-Wiedemann, Denys-Drash, Simpson-Golabi-Behmel, Perlman and possibly Meacham-Winn syndromes. Simpson-Golabi-Behmel syndrome was felt to be the most likely diagnosis. If this opinion is correct, genital ambiguity, hydramnios and nephroblastomatosis should be added to the clinical spectrum of Simpson-Golabi-Behmel syndrome. Differential diagnosis between the above-mentioned syndromes is of major importance for accurate genetic counseling, considering the differences in recurrence risk. The present case underlines the need for long-term survey of patients suspected of having Simpson-Golabi-Behmel syndrome, who could be at risk for embryonic tumours.