Weaver syndrome: autosomal dominant inheritance of the disorder

Intrauterine growth in chromatinopathies: A long road for better understanding and for improving clinical management

BACKGROUND

Chromatinopathies are a heterogeneous group of genetic disorders caused by pathogenic variants in genes coding for chromatin state balance proteins. Remarkably, many of these syndromes present unbalanced postnatal growth, both under- and over-, although little has been described in the literature. Fetal growth measurements are common practice in pregnancy management and values within normal ranges indicate proper intrauterine growth progression; on the contrary, abnormalities in intrauterine fetal growth open the discussion of possible pathogenesis affecting growth even in the postnatal period.

METHODS

Among the numerous chromatinopathies, we have selected six of the most documented in the literature offering evidence about two fetal overgrowth (Sotos and Weaver syndrome) and four fetal undergrowth syndromes (Bohring Opitz, Cornelia de Lange, Floating-Harbor, and Meier Gorlin syndrome), describing their molecular characteristics, maternal biochemical results and early pregnancy findings, prenatal ultrasound findings, and postnatal characteristics.

RESULTS/CONCLUSION

To date, the scarce data in the literature on prenatal findings are few and inconclusive, even though these parameters may contribute to a more rapid and accurate diagnosis, calling for a better and more detailed description of pregnancy findings.

Macrocephaly and Finger Changes: A Narrative Review

Macrocephaly, characterized by an abnormally large head circumference, often co-occurs with distinctive finger changes, presenting a diagnostic challenge for clinicians. This review aims to provide a current synthetic overview of the main acquired and genetic etiologies associated with macrocephaly and finger changes. The genetic cause encompasses several categories of diseases, including bone marrow expansion disorders, skeletal dysplasias, ciliopathies, inherited metabolic diseases, RASopathies, and overgrowth syndromes. Furthermore, autoimmune and autoinflammatory diseases are also explored for their potential involvement in macrocephaly and finger changes. The intricate genetic mechanisms involved in the formation of cranial bones and extremities are multifaceted. An excess in growth may stem from disruptions in the intricate interplays among the genetic, epigenetic, and hormonal factors that regulate human growth. Understanding the underlying cellular and molecular mechanisms is important for elucidating the developmental pathways and biological processes that contribute to the observed clinical phenotypes. The review provides a practical approach to delineate causes of macrocephaly and finger changes, facilitate differential diagnosis and guide for the appropriate etiological framework. Early recognition contributes to timely intervention and improved outcomes for affected individuals.

Posteromedial Hypothalamic Deep Brain Stimulation for Refractory Aggressiveness in a Patient With Weaver Syndrome: Clinical, Technical Report and Operative Video

BACKGROUND AND IMPORTANCE

Deep brain stimulation of the posteromedial hypothalamus (PMH DBS) appears to be an effective treatment for drug-resistant aggressiveness. Weaver syndrome (WS) is a rare genetic disorder in which patients develop some degree of intellectual disability and rarely severe behavioral alterations that may benefit from this procedure.

CLINICAL PRESENTATION

We present the case of a 26-yr-old man diagnosed with WS presenting with uncontrollable self and heteroaggressiveness and disruptive behavior refractory to pharmacological treatment and under severe physical and mechanical restraining measures. The patient was successfully treated with bilateral PMH DBS resulting in affective improvement, greater tolerance for signs of affection, regularization in his sleep pattern and appetite disturbances at 12-mo follow-up. A detailed description and video of the procedure are presented, and a review of the clinical characteristics of WS and the utility and benefits of PMH DBS for refractory aggressiveness are reviewed.

CONCLUSION

To our knowledge, this is the first case of refractory aggressiveness described in WS as well as the first patient with WS successfully treated with PMH DBS.

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.

Mutations in genes encoding polycomb repressive complex 2 subunits cause Weaver syndrome

Weaver syndrome (WS) is a rare congenital overgrowth disorder caused by heterozygous mutations in EZH2 (enhancer of zeste homolog 2) or EED (embryonic ectoderm development). EZH2 and EED are core components of the polycomb repressive complex 2 (PRC2), which possesses histone methyltransferase activity and catalyzes trimethylation of histone H3 at lysine 27. Here, we analyzed eight probands with clinically suspected WS by whole-exome sequencing and identified three mutations: a 25.4-kb deletion partially involving EZH2 and CUL1 (individual 1), a missense mutation (c.707G>C, p.Arg236Thr) in EED (individual 2), and a missense mutation (c.1829A>T, p.Glu610Val) in SUZ12 (suppressor of zeste 12 homolog) (individual 3) inherited from her father (individual 4) with a mosaic mutation. SUZ12 is another component of PRC2 and germline mutations in SUZ12 have not been previously reported in humans. In vitro functional analyses demonstrated that the identified EED and SUZ12 missense mutations cause decreased trimethylation of lysine 27 of histone H3. These data indicate that loss-of-function mutations of PRC2 components are an important cause of WS.

Novel EED mutation in patient with Weaver syndrome

Weaver syndrome is a rare condition characterized by overgrowth, macrocephaly, accelerated osseous maturation, variable intellectual disability, and characteristic facial features. Pathogenic variants in EZH2, a histone methyltransferase, have previously been identified as a cause of Weaver syndrome. However, the underlying molecular cause in many patients remains unknown. We report a patient with a clinical diagnosis of Weaver syndrome whose exome was initially non-diagnostic. Reports in the medical literature of EED associated overgrowth prompted re-analysis of the patient's original exome data. The patient was found to have a likely pathogenic variant in EED. These findings support that Weaver syndrome is a disorder with locus heterogeneity and can be due to pathogenic variants in either EZH2 or EED. This case highlights the utility of exome sequencing as a clinical diagnostic tool for novel gene discovery as well as the importance of re-examination of exome data as new information about gene-disease associations becomes available. © 2016 Wiley Periodicals, Inc.

EZH2 mutation in an adolescent with Weaver syndrome developing acute myeloid leukemia and secondary hemophagocytic lymphohistiocytosis

Weaver syndrome is an overgrowth syndrome characterized by pre- and postnatal overgrowth with distinctive craniofacial appearance. Mutations in the enhancer of zeste homolog 2 (EZH2) gene were found to cause Weaver syndrome, and have been associated with hematologic malignancies, including acute myeloid leukemia (AML). We present the first report of a patient with Weaver syndrome, who developed AML and harbored an EZH2 mutation. The clinical course of the 16-year-old female adolescent patient was complicated by a secondary hemophagocytic lymphohistiocytosis. Genomic DNA was isolated from bone marrow cells at AML diagnosis. Polymerase chain reactions were performed with primers covering all exons of the EZH2 gene. We found a novel heterozygous EZH2 mutation within exon 5 that caused an amino acid change from proline to leucine at position 132 (p.Pro132Leu) within the catalytic D1 domain. Analysis of a remission sample also showed this mutation, indicating a germline mutation. It remains to be elucidated whether EZH2 mutations contribute to disease severity in specific AML cases.

Weaver syndrome and EZH2 mutations: Clarifying the clinical phenotype

Weaver syndrome, first described in 1974, is characterized by tall stature, a typical facial appearance, and variable intellectual disability. In 2011, mutations in the histone methyltransferase, EZH2, were shown to cause Weaver syndrome. To date, we have identified 48 individuals with EZH2 mutations. The mutations were primarily missense mutations occurring throughout the gene, with some clustering in the SET domain (12/48). Truncating mutations were uncommon (4/48) and only identified in the final exon, after the SET domain. Through analyses of clinical data and facial photographs of EZH2 mutation-positive individuals, we have shown that the facial features can be subtle and the clinical diagnosis of Weaver syndrome is thus challenging, especially in older individuals. However, tall stature is very common, reported in >90% of affected individuals. Intellectual disability is also common, present in ~80%, but is highly variable and frequently mild. Additional clinical features which may help in stratifying individuals to EZH2 mutation testing include camptodactyly, soft, doughy skin, umbilical hernia, and a low, hoarse cry. Considerable phenotypic overlap between Sotos and Weaver syndromes is also evident. The identification of an EZH2 mutation can therefore provide an objective means of confirming a subtle presentation of Weaver syndrome and/or distinguishing Weaver and Sotos syndromes. As mutation testing becomes increasingly accessible and larger numbers of EZH2 mutation-positive individuals are identified, knowledge of the clinical spectrum and prognostic implications of EZH2 mutations should improve.

Germline mutations in the oncogene EZH2 cause Weaver syndrome and increased human height

The biological processes controlling human growth are diverse, complex and poorly understood. Genetic factors are important and human height has been shown to be a highly polygenic trait to which common and rare genetic variation contributes. Weaver syndrome is a human overgrowth condition characterised by tall stature, dysmorphic facial features, learning disability and variable additional features. We performed exome sequencing in four individuals with Weaver syndrome, identifying a mutation in the histone methyltransferase, EZH2, in each case. Sequencing of EZH2 in additional individuals with overgrowth identified a further 15 mutations. The EZH2 mutation spectrum in Weaver syndrome shows considerable overlap with the inactivating somatic EZH2 mutations recently reported in myeloid malignancies. Our data establish EZH2 mutations as the cause of Weaver syndrome and provide further links between histone modifications and regulation of human growth.

Commonest overgrowth syndromes

Overgrowth syndromes, although rare, are diagnosed more frequently lately. Major progress, such as the identification of genetic causes, has recently enhanced the delineation of the characteristic and noncharacteristic manifestations, phenotype-genotype correlations and knowledge of the underlying pathophysiologic mechanisms. This review provides a summary of the most important overgrowth syndromes aiming to familiarize the treating physician with the cardinal clinical features involved in these syndromes that encompass overgrowth, but also have a variety of other clinical manifestations (neurologic, musculoskeletal, skin, and accompanying tumors).

Mutations in EZH2 cause Weaver syndrome

We used trio-based whole-exome sequencing to analyze two families affected by Weaver syndrome, including one of the original families reported in 1974. Filtering of rare variants in the affected probands against the parental variants identified two different de novo mutations in the enhancer of zeste homolog 2 (EZH2). Sanger sequencing of EZH2 in a third classically-affected proband identified a third de novo mutation in this gene. These data show that mutations in EZH2 cause Weaver syndrome.

The upper airway in Weaver syndrome

Weaver syndrome is a rare disorder of unknown etiology characterized by skeletal overgrowth, distinctive craniofacial and digital abnormalities, and advanced bone age. The prime anesthetic problem reported in children with Weaver syndrome is difficulty with tracheal intubation, resulting in part from relative micrognathia, short neck, and an anterior and cephalad position of the larynx. In this report, the authors describe their experience with two children diagnosed with Weaver syndrome who presented for dental surgery. Contrary to previous reports, tracheal intubation was accomplished with relative ease, suggesting that difficulty in intubation in Weaver syndrome may be age-related, diminishing with advancing age and growth of the mandible, as has been reported for other micrognathic syndromes such as Pierre Robin sequence.

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.

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.

NSD1 mutations are the major cause of Sotos syndrome and occur in some cases of Weaver syndrome but are rare in other overgrowth phenotypes

Sotos syndrome is a childhood overgrowth syndrome characterized by a distinctive facial appearance, height and head circumference >97th percentile, advanced bone age, and developmental delay. Weaver syndrome is characterized by the same criteria but has its own distinctive facial gestalt. Recently, a 2.2-Mb chromosome 5q35 microdeletion, encompassing NSD1, was reported as the major cause of Sotos syndrome, with intragenic NSD1 mutations identified in a minority of cases. We evaluated 75 patients with childhood overgrowth, for intragenic mutations and large deletions of NSD1. The series was phenotypically scored into four groups, prior to the molecular analyses: the phenotype in group 1 (n=37) was typical of Sotos syndrome; the phenotype in group 2 (n=13) was Sotos-like but with some atypical features; patients in group 3 (n=7) had Weaver syndrome, and patients in group 4 (n=18) had an overgrowth condition that was neither Sotos nor Weaver syndrome. We detected three deletions and 32 mutations (13 frameshift, 8 nonsense, 2 splice-site, and 9 missense) that are likely to impair NSD1 functions. The truncating mutations were spread throughout NSD1, but there was evidence of clustering of missense mutations in highly conserved functional domains between exons 13 and 23. There was a strong correlation between presence of an NSD1 alteration and clinical phenotype, in that 28 of 37 (76%) patients in group 1 had NSD1 mutations or deletions, whereas none of the patients in group 4 had abnormalities of NSD1. Three patients with Weaver syndrome had NSD1 mutations, all between amino acids 2142 and 2184. We conclude that intragenic mutations of NSD1 are the major cause of Sotos syndrome and account for some Weaver syndrome cases but rarely occur in other childhood overgrowth phenotypes.

The difficulty of height prediction in Weaver syndrome

Accelerated growth and advanced bone age are consistent findings in Weaver-Smith syndrome (WSS). According to the rather scant reports in the literature, persons afflicted with WSS appear to achieve supranormal heights despite a significant bone age advancement in their growth period. The literature does not state clearly whether there is a discrepancy between bone age advancement and the time of onset of puberty in WSS. We report a girl with Weaver syndrome whose final height predictions were within normal limits according to the standard prediction models, who had to be eventually treated with high doses of estrogen in order to keep her final height within reasonable limits. We conclude that the pattern of growth and maturation in children with WSS may form an exception to the general rule that tall children with an advanced bone age mature early and thus attain a normal final height. A careful evaluation of growth data of other children with WSS is necessary to clarify this issue.

Prenatal findings on ultrasound and X-ray in a case of overgrowth syndrome associated with increased nuchal translucency

A case of prenatal diagnosis of an overgrowth syndrome at 30 weeks of gestation is reported. The diagnosis was suggested on the basis of increased fetal growth from 16 weeks onwards, advanced bone age, and characteristic facial features such as hypertelorism, broad forehead and small chin. The fetus presented at 12 weeks with a markedly increased nuchal translucency thickness and generalized skin edema, but normal karyotype. Serial ultrasound scans revealed brain abnormalities including mild unilateral ventriculomegaly and a cyst in the cavum septi pellucidi. The pregnancy was terminated at the parents' request at 32 weeks of gestation and postmortem examination confirmed the prenatal findings. This case demonstrates the possibility of prenatal diagnosis of early overgrowth syndromes and highlights the dilemma arising from the prenatal diagnosis of a non-lethal condition associated with an uncertain prognosis and poorly documented in utero.

Cervical spine anomalies and tumors in Weaver syndrome

Weaver syndrome is an autosomal dominant disorder comprising accelerated growth rate and rapidly advancing skeletal maturation. Previous reports suggest that the phenotype in adults may be sufficiently subtle to make diagnosis difficult. Half brothers with classical childhood findings of Weaver syndrome and their father with minimal clinical findings showed cervical spine anomalies that likely represent a consistent radiographic finding in this disorder. One of the children represents the third occurrence of neoplasia in Weaver syndrome.

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.