Twins and their mildly affected mother with Weaver syndrome

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.

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.

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.

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.

Excessive growth in a girl with Weaver syndrome

A 24 month-old female with Weaver syndrome who has the most severe overgrowth among reported cases is presented. Prenatal history was remarkable for maternal hydantoin use throughout pregnancy. In addition to all major features of the syndrome, she displayed some novel features, including patent ductus arteriosus, atrial septal defect and diffuse thinning of the corpus callosum. Initially, carpal bone age was more advanced compared to phalangeal bone age, as expected in Weaver syndrome. However, phalangeal bone age caught up with carpal bone age during the follow-up period, suggesting that dysharmonic bone age advancement is an early feature of Weaver syndrome. The apparent male predominance in Weaver syndrome is generally ascribed to milder expression of the syndrome in females. The present patient, showing the most severe expression of the syndrome, refutes the notion that females with Weaver syndrome may have a milder form of the syndrome.

Weaver syndrome: autosomal dominant inheritance of the disorder

Weaver syndrome (WS), a condition first described in 1974 by Weaver et al., consists of macrosomia, advanced skeletal age, characteristic pattern of facial and radiographic anomalies, and contractures. Although there have been three reports of close relatives (sibs or both parent and offspring) affected with this condition, the syndrome generally occurs sporadically, and the recurrence risk in sporadic cases appears to be low. We report here on a family in which the propositus and his sister were born with the facial phenotype, club feet, and macrosomia characteristic of WS. Their father had macrosomia and macrocephaly as an adult, and childhood photos show clearly that he has WS. Two sisters of the propositus have had normal growth and development. The syndrome in this family appears to be inherited in an autosomal dominant fashion.

Familial neurofibromatosis type 1 associated with an overgrowth syndrome resembling Weaver syndrome

The simultaneous occurrence of familial neurofibromatosis type 1 (NF1) and an overgrowth syndrome resembling Weaver syndrome was observed in two related cases (a mother and her son). NF1 was confirmed by molecular genetic analysis showing a large deletion at 17q11.2, encompassing the entire NF1 gene. The other symptoms in the two cases were similar to the features reported in Weaver syndrome. Although the combination of NF1 and an overgrowth syndrome resembling Weaver syndrome in this family may be fortuitous, we favour the hypothesis that the deletion of the entire gene has caused this combined phenotype. Possible pathogenetic mechanisms are discussed. The observation suggests a relation between NF1 with an extraordinarily large gene deletion and a Weaver(-like) syndrome. This warrants investigation for deletions in the 17q11.2 region in Weaver(-like) syndrome patients.

Autosomal dominant inheritance of Weaver syndrome

Most report of Weaver syndrome have been sporadic cases and the genetic basis of the syndrome is uncertain. This report of an affected father and daughter provides evidence for autosomal dominant inheritance.

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.