Monozygotic twins discordant for Wiedemann-Beckwith syndrome and the implications for genetic counselling

Diagnosis and management of the phenotypic spectrum of twins with Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder with a heterogeneous phenotypic spectrum. There is an increased prevalence of monozygotic twinning in BWS. Given the epigenetic nature and phenotypic spectrum that defines BWS, twins are often discordant for clinical features, and clinicians are faced with the challenge of diagnosing and managing these twins. We present a cohort of multiple pregnancies in which one or more child from each pregnancy was diagnosed with BWS. We conducted a chart review of monochorionic and dichorionic gestations. Clinical scores for monochorionic twins demonstrated phenotypic discordance between the proband and twin. Based on linear regression analysis, a higher clinical score in the proband correlated with larger phenotypic discordance between twin siblings. Despite phenotypic discordance, however, we observed a consistent additive clinical score for a pregnancy (proband's plus twin's scores from a pregnancy). This idea of a finite degree of affectedness for a pregnancy implies a finite number of epigenetically affected cells. This further corroborates the idea that timing of monozygotic monochorionic twinning correlates with the disruption of establishment and/or maintenance of imprinting. The difference in clinical score between a proband and their twin may be due to diffused mosaicism, whereby there is an asymmetric distribution of affected cells among the multiple fetuses in a monozygotic monochorionic pregnancy, leading to a spectrum of variably affected phenotypes. Based on these findings, we recommend an algorithm for a conservative approach to clinically evaluate all children in a monozygotic multiple gestation affected by BWS.

Maternal Hypomethylation of KvDMR in a Monozygotic Male Twin Pair Discordant for Beckwith-Wiedemann Syndrome

Beckwith-Wiedemann syndrome (BWS; OMIM 130650) is a heterogeneous overgrowth syndrome characterized by visceromegaly, macroglossia, tumor predisposition, and other congenital abnormalities. BWS is usually associated with abnormalities of chromosome 11p15, including (epi)genetic changes, paternal disomy and point mutations. A number of identical twin pairs, mostly female, have been reported to be clinically discordant for BWS. Studies of monozygotic twins discordant for BWS provide more information about failure in the DNA methylation maintenance machinery during very early embryonic development. Here, we report a case of monozygotic male twins discordant for BWS phenotype. Methylation analysis of the 2 imprinted domains at 11p15.5 (H19DMR and KvDMR) was performed by methylation-specific MLPA and pyrosequencing of DNA extracted from peripheral blood and buccal swabs of both twins. Hypomethylation at KvDMR was identified in both cell types of the affected twin, whereas his healthy brother presented hypomethylation only in blood cells and a normal methylation profile in buccal swab. For diagnostic purposes, it is important to remember that twins can share fetal circulation and possibly share hematopoietic stem cells early in development; therefore, the affected and unaffected twins can share an epigenotype that will resemble partial hypomethylation. If a patient is a twin, it is valuable to obtain a sample from a tissue other than blood.

Identical but not the same: the value of discordant monozygotic twins in genetic research

Monozygotic (MZ) twins show remarkable resemblance in many aspects of behavior, health, and disease. Until recently, MZ twins were usually called "genetically identical"; however, evidence for genetic and epigenetic differences within rare MZ twin pairs has accumulated. Here, we summarize the literature on MZ twins discordant for Mendelian inherited disorders and chromosomal abnormalities. A systematic literature search for English articles on discordant MZ twin pairs was performed in Web of Science and PubMed. A total number of 2,016 publications were retrieved and reviewed and 439 reports were retained. Discordant MZ twin pairs are informative in respect to variability of phenotypic expression, pathogenetic mechanisms, epigenetics, and post-zygotic mutagenesis and may serve as a model for research on genetic defects. The analysis of single discordant MZ twin pairs may represent an elegant approach to identify genes in inherited disorders.

Addition of H19 'loss of methylation testing' for Beckwith-Wiedemann syndrome (BWS) increases the diagnostic yield

Beckwith-Wiedemann syndrome (BWS) is a clinical diagnosis; however, molecular confirmation via abnormal methylation of DMR2(LIT1) and/or DMR1(H19) has clinical utility due to epigenotype-tumor association. Despite the strong link between H19 hypermethylation and tumor risk, several diagnostic laboratories only test for hypomethylation of LIT1. We assessed the added diagnostic value of combined LIT1 and H19 testing in a large series of referred samples from 1298 patients, including 53 well-characterized patients from the St. Louis Children's Hospital BWS-Registry (validation samples) and 1245 consecutive nationwide referrals (practice samples). Methylation-sensitive enzymatic digestion with Southern hybridization assessed loss of normal imprinting. In the validation group, abnormal LIT1 hypomethylation was detected in 60% (32/52) of patients but LIT1/H19-combined testing was abnormal in 68% (36/53); sensitivity in the practice setting demonstrated 27% (342/1245) abnormal LIT1 and 32% (404/1245) abnormal LIT1/H19-combined. In addition, H19 methylation was abnormal in 7% of LIT1-normal patients. We observed absence of uniparental disomy (UPD) in 27% of combined LIT1/H19-abnormal samples, diagnostic of multilocus methylation abnormalities; in contrast to studies implicating that combined LIT1/H19 abnormalities are diagnostic of UPD. The overall low detection rate, even in validated patient samples and despite characterization of both loci and UPD status, emphasizes the importance of clinical diagnosis in BWS.

Methylation analysis of 79 patients with growth restriction reveals novel patterns of methylation change at imprinted loci

This study was an investigation of 79 patients referred to the Wessex Regional Genetics Laboratory with suspected Russell-Silver Syndrome or unexplained short stature/intra uterine growth restriction, warranting genetic investigation. Methylation status was analysed at target sequences within eleven imprinted loci (PLAGL1, IGF2R, PEG10, MEST1, GRB10, KCNQ1OT1, H19, IGF2P0, DLK1, PEG3, NESPAS). Thirty seven percent (37%) (29 of 79) of samples were shown to have a methylation abnormality. The commonest finding was a loss of methylation at H19 (23 of 29), as previously reported in Russell-Silver Syndrome. In addition, four of these patients had methylation anomalies at other loci, of whom two showed hypomethylation of multiple imprinted loci, and two showed a complete gain of methylation at IGF2R. This latter finding was also present in five other patients who did not have demonstrable changes at H19. In total, 7 of 79 patients showed a gain of methylation at IGF2R and this was significantly different from a normal control population of 267 individuals (P=0.002). This study in patients with growth restriction shows the importance of widening the epigenetic investigation to include multiple imprinted loci and highlights potential involvement of the IGF2R locus.

Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is a clinically heterogeneous overgrowth syndrome associated with an increased risk for embryonal tumor development. BWS provides an ideal model system to study epigenetic mechanisms. This condition is caused by a variety of genetic or epigenetic alterations within two domains of imprinted growth regulatory genes on human chromosome 11p15. Molecular studies of BWS have provided important data with respect to epigenotype/genotype-phenotype correlations; for example, alterations of Domain 1 are associated with the highest risk for tumor development, specifically Wilms' tumor. Further, the elucidation of the molecular basis for monozygotic twinning in BWS defined a critical period for imprint maintenance during pre-implantation embryonic development. In the future, such molecular studies in BWS will permit enhanced medical management and targeted genetic counseling.

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.

Imprinting errors and developmental asymmetry

There are, in the broadest sense, two mechanisms by which gene expression can be extinguished in vertebrates. The first of these is based on mass action effects of positive and negative regulatory factors and is termed activation and repression; the second is independent of positive regulatory factors but is based on the history of the affected gene and is termed silencing. It can be said, again in the broadest sense, that imprinted genes, genes subject to X inactivation, and transposon promoters are subject to silencing, while the promoters of tissue-specific genes in non-expressing tissues are controlled by activation and repression. The escape of imprinted genes from silencing through unknown mechanisms can cause developmental abnormalities and can predispose to the formation of embryonal tumours. One developmental disorder caused by loss of imprinting of genes on chromosome 11p15.5 is Beckwith-Wiedemann syndrome (BWS). This syndrome has long been known to be inexplicably common in monozygotic twins; the twins are nearly always discordant for BWS, and nearly all twins are female. A loss of imprinting model based on stochastic errors in the nucleocytoplasmic trafficking of the DNA methyltransferase DNMT1, or a paternally expressed function that opposes maintenance methylation of maternally repressed growth-enhancing genes, is proposed to explain the perplexing genetics of BWS in monozygotic twins.

Mosaic trisomy 11p in monozygotic twins with discordant clinical phenotypes

We report on monozygotic (MZ) twins with a de novo mos 46,XX,der(15)t(11;15)(p12;p11.2)/46,XX karyotype varying in different tissues. The clinical presentation and findings at the cytogenetic level are described. One of the infants had definite minor anomalies at birth, also found in other cases of trisomy of 11p resembling the Beckwith-Wiedemann syndrome. Theoretical backgrounds regarding the string of events leading to the cytogenetic findings in these twins and the various factors that might have contributed to the dissimilarities in phenotype between these twins are discussed.

Canalization, developmental stability, and morphological integration in primate limbs

Canalization and developmental stability refer to the tendency of developmental processes to follow particular trajectories, despite external or internal perturbation. Canalization is the tendency for development of a specific genotype to follow the same trajectory under different conditions (different environments or different genetic backgrounds), while developmental stability is the tendency for the development of a specific genotype to follow the same trajectory under the same conditions. Morphological integration refers to the tendency for structures to show correlated variation because they develop in response to shared developmental processes or function in concert with other structures. All three phenomena are emergent properties of developmental systems that can affect the interaction of development and evolution. In this paper, we review the topics of canalization, developmental stability, and morphological integration and their relevance to primate and human evolution. We then test three developmentally motivated hypotheses about the patterning of variability components in the mammalian limb. We find that environmental variances and fluctuating asymmetries (FA) increase distally along the limb in adult macaques but not in fetal mice. We infer that the greater variability of more distal segments in macaques is due to postnatal mechanical effects. We also find that heritability and FA are significantly correlated when different limb measurements are compared in fetal mice. This supports the idea that the mechanisms underlying canalization and developmental stability are related. Finally, we report that the covariation structure of fore- and hindlimb skeletal elements shows evidence for morphological integration between serially homologous structures between the limbs. This is evidence for the existence of developmental modules that link structures between the limbs. Such modules would produce covariation that would need to be overcome by selection for divergence in hind- and forelimb morphology.

Two pairs of male monozygotic twins discordant for Wiedemann-Beckwith syndrome

Wiedemann-Beckwith syndrome (WBS) is a congenital anomaly syndrome which classically consists of exomphalos, macroglossia, and gigantism. The syndrome is also associated with a variety of minor anomalies and affected individuals have an increased risk of developing rare embryonal cell tumors. To date, 15 monozygotic (MZ) twin pairs have been reported of which 13 are discordant for WBS. All except one pair of the discordant WBS twin pairs have been female. We report two pairs of male MZ twins, each discordant for WBS.

Longitudinal observations on 15 children with Wiedemann-Beckwith syndrome

We conducted a follow-up study on 15 patients with Wiedemann-Beckwith syndrome (WBS) to further clarify major and minor diagnostic clinical characteristics and longterm expectations for growth and development. We found patients with WBS tended to have polyhydramnios with large placentas which were almost twice normal placental weight. The large fetal size and polyhydramnios often resulted in early delivery with occasional perinatal mortality (three cases). Increased placental size, with associated polyhydramnios resulting in excessive umbilical cord length, may be useful in suspecting WBS prior to delivery, thereby facilitating perinatal management. The presence of abdominal wall defects and/or macroglossia may help to confirm the diagnosis. At birth, patients were almost 2 standard deviations above the expected mean for gestational age, length, and weight. This trend continued through early childhood and then excessive size became less dramatic with increasing age. We detected no cytogenetic variations in nine patients who had studies done and, to date, no tumors have been detected other than a gastric teratoma that was evident in one infant at birth. Longitudinally, the children have not had an unusual incidence of medical problems, and long-term ultrasound monitoring was not burdensome to the families. In comparison, mental and social development to unaffected siblings and cousins appeared normal.

Non-random X chromosome inactivation in an affected twin in a monozygotic twin pair discordant for Wiedemann-Beckwith syndrome

Wiedemann-Beckwith syndrome (WBS) is a syndrome including exomphalos, macroglossia, and generalized overgrowth. The locus has been assigned to 11p15.5, and genomic imprinting may play a part in the expression of one or more genes involved. Most cases are sporadic. An excess of female monozygotic twins discordant for WBS have been reported, and it has been proposed that this excess could be related to the process of X chromosome inactivation. We have therefore studied X chromosome inactivation in 13-year-old monozygotic twin girls who were discordant for WBS. In addition, both twins had Tourette syndrome. The twins were monochorionic and therefore the result of a late twinning process. This has also been the case in previously reported discordant twin pairs with information on placentation. X chromosome inactivation was determined in DNA from peripheral blood cells by PCR analysis at the androgen receptor locus. The affected twin had a completely skewed X inactivation, where the paternal allele was on the active X chromosome in all cells. The unaffected twin had a moderately skewed X inactivation in the same direction, whereas the mother had a random pattern. Further studies are necessary to establish a possible association between the expression of WBS and X chromosome inactivation.

Clinical features and natural history of Beckwith-Wiedemann syndrome: presentation of 74 new cases

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth syndrome with variable expression. To define the range and frequency of complications in BWS, we have studied a cohort of 76 affected patients (two previously reported). The most frequent complications were macroglossia (97%), abdominal wall defect (80%) and birth weight or postnatal growth > 90th centile (88%). Other common features were ear creases/pits (76%), facial naevus flammeus (62%), nephromegaly (59%) and hypoglycaemia (63%). Rarer complications included hemihypertrophy (24%), moderate/severe developmental delay (4%), congenital heart defects (6.5%), polydactyly (4%), neoplasia (4%) and cleft palate (2.5%). Pre-term labour occurred in 53% and polyhydramnios in 33% of BWS pregnancies. The six deaths all occurred in babies born pre-term, three of whom had major congenital abnormalities. Five patients (6.5%) from four kindreds had an unequivocal family history of BWS, but 15 of 68 apparently sporadic cases had a relative with possible BWS (minor features only). Incomplete penetrance may lead to familial BWS being underdiagnosed.

Molecular analysis of patients with Wiedemann-Beckwith syndrome. I. Gene dosage on the short arm of chromosome 11

Wiedemann-Beckwith syndrome (WBS) is characterised by a specific group of congenital malformations associated with an increased concurrent risk for development of a defined group of childhood neoplasms. The mode of inheritance is complex, but recently compiled family data suggest that it is an autosomal dominant trait of varying expression. It has previously been suggested that major rearrangements on the short arm of chromosome 11 may be involved in the aetiology of the disease, particularly in the region of the insulin like growth factor II (IGF-II) gene (11p15.5). This gene is thought to be parentally imprinted in the mouse and it has been suggested that in the human, duplication of the non-imprinted locus in WBS patient might lead to diploid expression of the gene and consequent general hyperplasia. This model predicts that there should be both frequent and parental origin specific duplication of the IGF-II gene in the patients. It was the aim of this study to examine the IGF-II locus and its surrounding chromosomal environment for such lesions in a large number of WBS patients. Using restriction fragment length polymorphism analysis for four linked markers on 11p and genomic clones internal to the IGF-II locus we could find no evidence of alteration or amplification of this area in any of the 11 patients investigated. In one patient who developed a Wilms tumour we could find no evidence for loss of any material on the short arm of chromosome 11 as reported previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Beckwith-Wiedemann syndrome, tumourigenesis and imprinting

The concurrent development of cytogenetic, clinical, genetic and molecular studies has led to the recognition that the different hereditary and non-hereditary forms of the Beckwith-Wiedemann syndrome and associated tumours result from an imbalance between maternal and paternal alleles. The most exciting development in the past year was the discovery of uniparental paternal disomy and the increased understanding, arising from studies in the mouse and in hereditary cases, of the role possibly played by imprinting and somatic mosaicism in partial and complete expression of this complex syndrome.

Evidence for paternal imprinting in familial Beckwith-Wiedemann syndrome

A previously unreported family in which seven members in two generations have Beckwith-Wiedemann syndrome (BWS) is documented. Paternal imprinting of the gene responsible for BWS is involved as the mechanism responsible for the aberrant inheritance pattern in this kindred. A review of published reports showed 27 previously published pedigrees with two or more affected subjects with BWS. Paternal imprinting would explain the non-mendelian inheritance of BWS in all but four kindreds. The latter families are examined in more detail and in only one example is the evidence against imprinting totally unexplained.

Monozygotic twinning and Wiedemann-Beckwith syndrome

Monozygotic (MZ) twinning occurs with relatively high frequency in Wiedemann-Beckwith syndrome (WBS). Ten sets of MZ twins with WBS have been reported. Nine of these have been female and in each case the twins were discordant for the WBS phenotype. The tenth set was male. They were concordant for WBS and both had a duplication of chromosome 15 which they shared in common with their phenotypically normal mother. The WBS gene has been assigned to the locus 11p15 and there appear to be several different genetic mechanisms involving this locus which all give rise to WBS. An imprinting effect for the WBS gene has been proposed because of the transmission of the gene preferentially through the maternal line in some large pedigrees. We describe two further sets of female MZ twins with WBS. One pair is concordant and one discordant for the condition. The possible genetic mechanisms involved in the expression of WBS are discussed, with particular reference to twinning, genomic imprinting and X-inactivation which is thought to be associated with the occurrence of MZ twinning in females.

Prenatal diagnosis in autosomal dominant Beckwith-Wiedemann syndrome

A 20-year-old woman with Beckwith-Wiedemann syndrome (BWS) was ultrasonographically appraised at intervals during her pregnancy. Unequivocal evidence for a diagnosis of BWS was obtained in the fetus and this was confirmed postnatally. Early ultrasound diagnosis enabled appropriate genetic counselling to be given; neonatal complications, such as hypoglycaemic episodes, were prevented.

Congenital gastric teratoma in Wiedemann-Beckwith syndrome

Wiedemann-Beckwith syndrome (WBS) may be associated with abdominal tumors, including Wilms tumor, adrenocortical carcinoma, hepatoblastoma, gonadoblastoma, rhabdomyosarcoma, and neuroblastoma. We report on a newborn infant with WBS and a congenital teratoma of the stomach. This is the sole report of any teratoma being associated with WBS and also the first report of a tumor present at birth and visible prenatally in WBS. At birth this infant boy had the diagnostic findings of WBS with macroglossia, ear lobule creases and pits, nevus flammeus, and omphalocele, and an abdominal mass. Abnormalities were detected prenatally when ultrasound examination showed placental overgrowth, polyhydramnios, omphalocele, and posterior abdominal calcifications. Resection of the mass and partial gastrectomy were performed at age 10 days; histologic study showed an immature grade-II teratoma containing a mixture of mature and immature tissues from all germ layers. Results of cytogenetic studies of blood and teratoma were normal (46,XY). This congenital gastric teratoma in a newborn boy with classical WBS may represent either a tumor or an included twin. We discuss its implications for the association of WBS with neoplasia and monozygotic (MZ) twinning, review various neoplasias associated with WBS, and consider pathogenetic mechanisms.

A possible relationship between Beckwith-Wiedemann syndrome, urinary tract anomaly and prune belly syndrome

We report here two siblings diagnosed as having Beckwith-Wiedemann syndrome. In addition to Beckwith-Wiedemann syndrome, one of the siblings was also diagnosed with prune belly syndrome. The other sibling suffered from obstructive uropathy and unilateral cryptorchidism, which are also seen in prune belly syndrome. We believe that these two cases point to a potential association between Beckwith-Wiedemann syndrome, prune belly syndrome, and urinary tract anomaly.

Definitive methods of zygosity determination in twins: relevance to problems in the biology of twinning

Many studies of embryogenesis and fate of twin pregnancies are invalidated because zygosity is not determined definitively, or is assumed on the basis of inadequate criteria. This paper briefly reviews methods of zygosity determination. It reports published results and a new series of twins in which zygosity was determined by DNA fingerprinting. Implications for methods of prenatal diagnosis of zygosity are discussed in the context of the occasional need for intervention in twin transfusion syndrome or in twins discordant for major malformations. Definitive zygosity and placental anatomy (number of chorions and amnions) is discussed as the firm substrate for studies of normal and abnormal twin development.

Dominant inheritance of Wiedemann-Beckwith syndrome: further evidence for transmission of "unstable premutation" through carrier women

We report on a 4-generation family in which the Wiedemann Beckwith syndrome (WBS) was transmitted as an autosomal dominant trait. The condition occurred in sibs born to carrier women and in children born to affected mothers. Presumptive carrier women were examined for microsigns of WBS in an attempt to determine whether extreme variability of the disorder, rather than an unaffected carrier state, was present. No minor stigmata of the WBS could be found in the presumptive carriers. Our study supports a previous hypothesis that in some families the WBS can be transmitted in a 2-step process involving first an unstable premutation and then a "telomutation." Because only females appear to be transmitters of the telomutation, an ovum-mediated sex-associated factor may be involved in the process of telomutation.

Analysis of gene dosage on chromosome 11 in children suffering from Beckwith-Wiedemann syndrome

The Beckwith-Wiedemann syndrome (BWS) is composed of multiple congenital malformations coupled with a high concurrent risk for the development of specific rare childhood tumours. The syndrome is characterised by a complex mode of inheritance, but recent evidence indicates that it is an autosomal dominant trait with variable penetrance. It has been previously suggested that major rearrangements of the short arm of chromosome 11 are involved in the aetiology of the disease. We undertook to search for rearrangements in 11p in four patients with BWS and their parents and siblings. By using cloned DNA fragments homologous to four genes located on 11p, namely catalase, parathyroid hormone, insulin-like growth factor II and the proto-oncogene c-Ha-Ras, we subjected DNA from the patients to a restriction fragment length polymorphism (RFLP) analysis after digestion with restriction enzymes. We found no evidence for any large scale deletions or amplifications in this chromosomal region. We therefore conclude that altered gene dosage is not, as has been suggested, a requirement for the development of BWS. This raises the question of whether some other molecular mechanism is responsible for the malformations observed.

Absence of detectable chromosomal and molecular abnormalities in monozygotic twins discordant for the Wiedemann-Beckwith syndrome

Monozygotic twins discordant for the Wiedemann-Beckwith syndrome (WBS) were studied by cytogenetic and molecular methods to determine if a genetic lesion could be detected in the affected child. Probes known to be localized on the short arm of chromosome 11 and a low copy-repetitive probe were used. No genetic lesions could be ascertained in normal or affected tissue obtained from the WBS twin.

Wiedemann-Beckwith syndrome

The Wiedemann-Beckwith syndrome (WBS) comprises an accumulation of multiple congenital anomalies. Exomphalos, macroglossia and gigantism are considered the most common manifestations, hence the alternative designation EMG-syndrome. The syndrome carries with it an increased risk of developing specific tumours. One of the more frequent metabolic changes is transient neonatal hypoglycaemia, the result of increased insulin secretion. Inheritance of the syndrome remains uncertain. Most cases are sporadic, but a number of familial cases have been reported. Present evidence suggests that WBS is an autosomal dominant trait with variable expressivity. This review summarizes the abundant literature on the subject and discusses recent molecular genetic developments that may explain the interrelationship between the clinical abnormalities, metabolic disturbances and development of tumours.

Wiedemann-Beckwith syndrome in apparently discordant monozygotic twins

We report 3 pairs of monozygotic (MZ) twins, one twin showing typical Wiedemann-Beckwith syndrome (WBS) with minimal or no expression of the condition in the co-twin. These cases are documented, and three previously reported MZ twin pairs are reviewed. Phenotypic concordance for this syndrome in MZ twin pairs has not been reported. Many cases of familial occurrence have been published and different modes of inheritance have been postulated. Based on the twin-twin variability seen in our patients, it seems the most likely mechanism of inheritance is an autosomal dominant mutation with environmental modification of expressivity, or reduced phenotrance.

Constitutional interstitial deletion of 11p11 and pericentric inversion of chromosome 9 in a patient with Wiedemann-Beckwith syndrome and hepatoblastoma

A constitutional interstitial deletion on the short arm of chromosome #11 and an inversion of the heterochromatin of chromosome #9 were detected in a 1.5-year-old boy with Wiedemann-Beckwith syndrome (WBS) and hepatoblastoma. Of 37 malignant and nine benign neoplasms reported in approximately 250 cases with complete and incomplete forms of WBS, this is the fourth patient with hepatoblastoma. To date, 28 cases of WBS have been cytogenetically investigated with banding techniques. Constitutional anomalies have been found in only nine cases: Various anomalies resulting in a common triplication of the 11p15 region in six cases, reciprocal translocations t(11;22) and t(X;1) and an inversion of chromosome #2 in the three remaining cases. Triplication 11p15 was only present in one of four cases with a tumor. The breakpoints of the unique del(11)(p11.1p11.2) present in our case are proximal to those of del(11p13-11p14) and dup(11p15) observed thus far in both the aniridia-Wilms' tumor association and in WBS. Inversion of chromosome #9--one of the heterochromatin variants associated with elevated chromosomal instability, increased congenital abnormalities, and cancer proneness--may have been causally connected with a genetic imbalance resulting in the de novo deletion of 11p11. Therefore, we suggest that in these high-risk groups, C-banding studies should be performed together with high resolution chromosome analysis in order to also reveal the incidence and significance of C-band variants in individuals with such cancer prone syndromes.

Wiedemann-Beckwith syndrome: presentation of clinical and cytogenetic data on 22 new cases and review of the literature

The main features of Wiedemann-Beckwith syndrome (WBS) include macroglossia, abdominal wall defects, visceromegaly, gigantism, hypoglycemia, ear creases, nevus flammeus, and mid-face hypoplasia. Twenty-two cases of WBS were examined clinically and cytogenetically, and compared to 226 previously reported cases. Aspects of the clinical evaluations are discussed. All individuals examined were chromosomally normal with no evidence of 11p abnormality as has been reported recently. The relevance of a possible relationship between clinical findings, chromosome abnormalities, and genes present on 11p is discussed. Transmission of this condition is most consistent with autosomal dominant inheritance with incomplete penetrance.

The Wiedemann-Beckwith syndrome: pedigree studies on five families with evidence for autosomal dominant inheritance with variable expressivity

We describe 18 individuals from five unrelated families with various manifestations of the Wiedemann-Beckwith syndrome. Pedigree analysis was performed on the 5 families and on another 19 families in the literature, each of which included more than one affected person. The following findings were obtained: 1) the clinical manifestations among the affected individuals were highly variable--those obvious in infancy tended to become less distinct with increasing age; 2) the syndrome was transmitted directly and vertically through three generations in four families, and through two generations in seven families; 3) male-to-male transmission was noted once; 4) the sex ratio in the affected individuals was not significantly different from 1; 5) the segregation ratio of the trait among the sibs of the probands was 0.571 +/- 0.066; 6) the affected + carrier/normal ratio was one among the offspring of the affected individuals and obligate carriers; 7) phenotrance (the expected presence of the trait in a generation) of the syndrome in the sibship of probands was complete, whereas that in earlier generations appeared low. The discrepancy is attributable to the lessening of the clinical features with increasing age as well as to a possibly less aggressive search for abnormalities in older generations. These findings indicate that the syndrome is an autosomal dominant trait with variable expressivity. High-resolution chromosome banding analysis in seven affected individuals and their respective parents showed no abnormalities.

Prenatal diagnosis of the Beckwith-Wiedemann syndrome

We report on the prenatal diagnosis of Beckwith-Wiedemann syndrome (BWS) in a pregnancy monitored because of a previously affected child. The proposita had classical stigmata of BWS including macroglossia, omphalocele, and typical ear creases. Chromosomes were 46,XX. Both parents and the extended maternal family were clinically normal. In a subsequent pregnancy by another father, the mother had serial ultrasound monitoring at 13.5, 18, and 19 weeks gestation which showed an enlarged abdominal circumference and a 2-cm omphalocele. At termination the female fetus weighed more than two times the expected weight, had striking hypertrophy of skeletal muscles, a protuberant abdomen, and a 2-cm omphalocele and characteristic facial appearance. Autopsy confirmed generalized organomegaly. This is the first report of the prenatal diagnosis of BWS prior to 20 weeks in an at-risk family. The recurrence in this family emphasizes the difficulty in providing accurate genetic recurrence risks in BWS and suggests that ultrasonographic prenatal diagnosis should be offered to families even when the case appears to be "sporadic."

Wiedemann-Beckwith syndrome in one of monozygotic twins

A pair of monozygotic twins discordant for Wiedemann-Beckwith syndrome is described. The probability of monozygosity is 0.995. This observation suggests that the syndrome is unlikely to be under single gene control and genetic counselling should be based on multifactorial inheritance.

The Wiedemann-Beckwith syndrome in four sibs including one with associated congenital hypothyroidism

Two boys and two girls from a sibship of six, affected with the Wiedemann-Beckwith syndrome (WBS), are reported. One of the patients also had congenital hypothyroidism, an association hitherto undescribed and possibly fortuitous. Neither stigmata of WBS in other family members nor parental consanguinity were found, indicating a possible autosomal dominant inheritance comprising either a delayed mutation of an unstable premutated gene or non-penetrance.

Abnormality of chromosome 11 in patients with features of Beckwith-Wiedemann syndrome

Two unrelated children with features of Beckwith-Wiedemann syndrome have been found to have partial duplication of chromosome 11p. A review of six other reported cases of partial duplication of 11 p revealed features of this syndrome not previously recognized. We suggest that karyotype studies with banding techniques should be done in children with features of Beckwith-Wiedemann syndrome and developmental delay or retardation.

Wiedemann-Beckwith syndrome: autosomal-dominant inheritance in a family

We report four additional cases of Wiedemann-Beckwith syndrome (WBS): A mother, her brother, and two of her children (half-sibs). Theories of the genetic transmission of the WBS are reviewed. The trait in this family appears to be an autosomal-dominant with variable expressivity. A theory of delayed mutation of an unstable premutated gene is discussed and an interpretation and observations are offered which could alter slightly the expected pattern of inheritance. Eighty-eight other family members were screened for evidence of WBS and noteworthy findings are presented.