Androgenetic/biparental mosaicism causes placental mesenchymal dysplasia

Placental mesenchymal disease masquerading as molar pregnancy with a favourable maternal and fetal outcome

Placental mesenchymal dysplasia (PMD) is an exceptionally rare placental anomaly characterised by placentomegaly and grape-like vesicles resembling partial mole on ultrasonography, yet it can coexist with a viable fetus. We present the case of a primigravida who presented at 22 weeks gestation with a suspected partial mole but with a normally growing fetus. The differential diagnoses considered included placental mesenchymal disease, partial mole and twin pregnancy with molar pregnancy. With normal beta HCG levels and prenatal invasive testing reports, a probable diagnosis of PMD was made, and after thorough counselling, the decision was made to continue the pregnancy. The pregnancy progressed until 37 weeks, culminating in the uneventful delivery of a 2.4 kg healthy male infant. Histopathology confirmed PMD. Early recognition and management of PMD pose significant challenges, given its rarity. Prenatal identification of PMD during both early and late gestation could avert unnecessary termination of pregnancy.

Prenatal detection of mosaicism for a genome wide uniparental disomy cell line in a cohort of patients: Implications and outcomes

OBJECTIVES

To investigate the prenatal detection rate of mosaicism by SNP microarray analysis, in which an individual has not one, but two, complete genomes (sets of DNA) in their body, a normal biparental line with a Genome Wide Uniparental Disomy (GWUPD) cell line was used.

METHODS

This study retrospectively examines the prenatal detection of GWUPD in a cohort of ∼90,000 prenatal specimens and ∼20,000 products of conceptions (POCs) that were studied by SNP microarray.

RESULTS

In total, 25 cases of GWUPD were detected; 16 cases were detected prenatally with GWUPD (∼0.018%) and 9 POCs revealed GWUPD (0.045%). The nine POC specimens presented with placental abnormalities. The 12 amniotic fluid specimens were ascertained because of abnormal ultrasound findings. Nine of 12 pregnancies had findings consistent with Beckwith-Wiedemann syndrome or because of abnormal placentas. However, three pregnancies were detected with GWUPD of maternal origin, with less common findings and demonstrated maternal origin. Four other pregnancies showed GWUPD in a chorionic villus sample, but normal findings in amniotic fluid and apparently normal fetal development.

CONCLUSIONS

This cohort with GWUPD mosaicism expands our understanding of GWUPD and has implications for prenatal care and counseling. Additional studies are necessary to understand the rarer maternal GWUPD.

Chimeric Singleton Placenta Comprising Placental Mesenchymal Dysplasia and Complete Hydatidiform Mole with Live Birth and Postpartum Diagnosis of Gestational Trophoblastic Neoplasia

INTRODUCTION

Placental mesenchymal dysplasia (PMD) is a benign lesion that is often misdiagnosed as complete (CHM) or partial hydatidiform mole. PMD usually results in live birth but can be associated with several fetal defects. Herein, we report PMD with CHM in a singleton placenta with live birth.

CASE PRESENTATION

A 34-year-old gravida 2, para 1, living 1 (G2P1L1) woman was referred on suspicion of a molar pregnancy in the first trimester. Maternal serum human chorionic gonadotrophin levels were increased during early pregnancy, with multicystic lesions and placentomegaly observed on ultrasonography. Levels decreased to normal with no fetal structural abnormalities observed. A healthy male infant was delivered at 34 gestational weeks. Placental p57KIP2 immunostaining and short tandem repeat analysis revealed three distinct histologies and genetic features: normal infant and placenta, PMD, and CHM. Gestational trophoblastic neoplasia was diagnosed and up to fourth-line chemotherapy administered.

CONCLUSION

Distinguishing PMD from hydatidiform moles is critical for avoiding unnecessary termination of pregnancy. CHM coexisting with a live fetus rarely occurs. This case is unique in that a healthy male infant was born from a singleton placenta with PMD and CHM.

Placental mesenchymal dysplasia complicated with sudden fetal demise and amniotic fluid embolism: a case report

BACKGROUND

Placenta mesenchymal dysplasia (PMD) is a rare placental anomaly associated with various fetal and maternal complications. Whether close ultrasound surveillance can prevent intrauterine fetal demise (IUFD) in patients with PMD is still under investigation. Amniotic fluid embolism (AFE) is a rare, lethal, and unpredictable maternal complication that has never been described in association with PMD. Here, we report a case of PMD, in which the fetus eventually demised in utero despite weekly color Doppler monitoring, and the mother subsequently encountered AFE during delivery.

CASE PRESENTATION

A 43-year-old woman who had received three frozen embryo transfer, was found to have a singleton pregnancy with an enlarged multi-cystic placenta at 8 weeks' gestation. Fetal growth restriction (FGR) was noted since the 21^stweek. The fetus eventually demised in-utero at 25 weeks despite weekly color Doppler surveillance. Cesarean section was performed under general anesthesia due to placenta previa totalis and antepartum hemorrhage. During surgery, the patient experienced a sudden blood pressure drop and desaturation followed by profound coagulopathy. AFE was suspected. After administration of inotropic agents and massive blood transfusion, the patient eventually survived AFE. PMD was confirmed after pathological examination of the placenta.

CONCLUSIONS

While FGR can be monitored by color Doppler, our case echoed previous reports that IUFD may be unpreventable even under intensive surveillance in PMD cases. Although AFE is usually considered unpredictable, PMD can result in cumulative risk factors contributing to AFE. Whether a specific link exists between the pathophysiology of PMD and AFE requires further investigation.

Placental Mesenchymal Dysplasia and Beckwith-Wiedemann Syndrome

Placental mesenchymal dysplasia (PMD) is characterized by placentomegaly, aneurysmally dilated chorionic plate vessels, thrombosis of the dilated vessels, and large grapelike vesicles, and is often mistaken for partial or complete hydatidiform mole with a coexisting normal fetus. Androgenetic/biparental mosaicism (ABM) has been found in many PMD cases. Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with complex and diverse phenotypes and an increased risk of developing embryonal tumors. There are five major causative alterations: loss of methylation of imprinting control region 2 (KCNQ1OT1:TSS-DMR) (ICR2-LOM), gain of methylation at ICR1 (H19/IGF2:IG-DMR) (ICR1-GOM), paternal uniparental disomy of 11 (pUPD11), loss-of-function variants of the CDKN1C gene, and paternal duplication of 11p15. Additional minor alterations include genetic variants within ICR1, paternal uniparental diploidy/biparental diploidy mosaicism (PUDM, also called ABM), and genetic variants of KCNQ1. ABM (PUDM) is found in both conditions, and approximately 20% of fetuses from PMD cases are BWS and vice versa, suggesting a molecular link. PMD and BWS share some molecular characteristics in some cases, but not in others. These findings raise questions concerning the timing of the occurrence of the molecularly abnormal cells during the postfertilization period and the effects of these abnormalities on cell fates after implantation.

Genetic variation in placental insufficiency: What have we learned over time?

Genetic variation shapes placental development and function, which has long been known to impact fetal growth and pregnancy outcomes such as miscarriage or maternal pre-eclampsia. Early epidemiology studies provided evidence of a strong heritable component to these conditions with both maternal and fetal-placental genetic factors contributing. Subsequently, cytogenetic studies of the placenta and the advent of prenatal diagnosis to detect chromosomal abnormalities provided direct evidence of the importance of spontaneously arising genetic variation in the placenta, such as trisomy and uniparental disomy, drawing inferences that remain relevant to this day. Candidate gene approaches highlighted the role of genetic variation in genes influencing immune interactions at the maternal-fetal interface and angiogenic factors. More recently, the emergence of molecular techniques and in particular high-throughput technologies such as Single-Nucleotide Polymorphism (SNP) arrays, has facilitated the discovery of copy number variation and study of SNP associations with conditions related to placental insufficiency. This review integrates past and more recent knowledge to provide important insights into the role of placental function on fetal and perinatal health, as well as into the mechanisms leading to genetic variation during development.

Parental genomes segregate into distinct blastomeres during multipolar zygotic divisions leading to mixoploid and chimeric blastocysts

Background

During normal zygotic division, two haploid parental genomes replicate, unite and segregate into two biparental diploid blastomeres.

Results

Contrary to this fundamental biological tenet, we demonstrate here that parental genomes can segregate to distinct blastomeres during the zygotic division resulting in haploid or uniparental diploid and polyploid cells, a phenomenon coined heterogoneic division. By mapping the genomic landscape of 82 blastomeres from 25 bovine zygotes, we show that multipolar zygotic division is a tell-tale of whole-genome segregation errors. Based on the haplotypes and live-imaging of zygotic divisions, we demonstrate that various combinations of androgenetic, gynogenetic, diploid, and polyploid blastomeres arise via distinct parental genome segregation errors including the formation of additional paternal, private parental, or tripolar spindles, or by extrusion of paternal genomes. Hence, we provide evidence that private parental spindles, if failing to congress before anaphase, can lead to whole-genome segregation errors. In addition, anuclear blastomeres are common, indicating that cytokinesis can be uncoupled from karyokinesis. Dissociation of blastocyst-stage embryos further demonstrates that whole-genome segregation errors might lead to mixoploid or chimeric development in both human and cow. Yet, following multipolar zygotic division, fewer embryos reach the blastocyst stage and diploidization occurs frequently indicating that alternatively, blastomeres with genome-wide errors resulting from whole-genome segregation errors can be selected against or contribute to embryonic arrest.

Conclusions

Heterogoneic zygotic division provides an overarching paradigm for the development of mixoploid and chimeric individuals and moles and can be an important cause of embryonic and fetal arrest following natural conception or IVF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02763-2.

Infantile hepatic hemangioma and hepatic mesenchymal hamartoma in an infant associated with placental mesenchymal dysplasia: a case report

Background

Although infantile hepatic hemangioma and hepatic mesenchymal hamartoma are relatively common in benign pediatric liver tumors, coexistence of the two tumors is rare. Placental mesenchymal dysplasia is also a rare disorder. We report the case of a baby girl born after a pregnancy complicated by placental mesenchymal dysplasia, who developed both infantile hepatic hemangioma and hepatic mesenchymal hamartoma.

Case presentation

The patient was born at 32 weeks and 5 days of gestation for impending placental abruption, weighing 1450 g. Liver tumors, composed of both hypervascular solid and large cystic lesions, were detected after birth and markedly increased to create abdominal distention within 9 months. Diagnostic imaging suspected the coexistence of infantile hepatic hemangioma and cystic hepatic mesenchymal hamartoma. Following propranolol therapy for infantile hepatic hemangioma and needle puncture of a large cyst, the cystic lesions and adjacent hypervascular lesions were partially resected via laparotomy. Pathological findings confirmed the coexistence of hepatic mesenchymal hamartoma and infantile hepatic hemangioma, which had no association with androgenetic/biparental mosaicism. The postoperative course was uneventful, and the tumor had not regrown after 3 years.

Conclusions

Although the coexistence of infantile hepatic hemangioma and hepatic mesenchymal hamartoma associated with placental mesenchymal dysplasia is extremely rare, the pathological and pathogenetic similarities between these disorders suggest that they could have derived from similar embryologic origins rather than being a mere coincidence. Further follow-up is required, with careful attention to the potential for malignant hepatic mesenchymal hamartoma transformation.

Gestational Trophoblastic Disease: Contemporary Diagnostic Approach

Pathologic diagnosis of gestational trophoblastic disease (GTD)-hydatidiform moles and gestational trophoblastic neoplasms-underwent a major shift in the past decade from morphology-based recognition to precise molecular genetic classification of entities, which also allows for prognostic stratification of molar gestations. This article highlights these recent advances and their integration into the routine pathology practice. The traditional gross and histomorphologic features of each entity are also reviewed with special focus on differential diagnoses and their clinical implications.

Aberrant hypomethylation at imprinted differentially methylated regions is involved in biparental placental mesenchymal dysplasia

BACKGROUND

Placental mesenchymal dysplasia (PMD) is a morphological abnormality resembling partial hydatidiform moles. It is often associated with androgenetic/biparental mosaicism (ABM) and complicated by Beckwith-Wiedemann syndrome (BWS), an imprinting disorder. These phenomena suggest an association between PMD and aberrant genomic imprinting, particularly of CDKN1C and IGF2. The existence of another type of PMD containing the biparental genome has been reported. However, the frequency and etiology of biparental PMD are not yet fully understood.

RESULTS

We examined 44 placental specimens from 26 patients with PMD: 19 of these were macroscopically normal and 25 exhibited macroscopic PMD. Genotyping by DNA microarray or short tandem repeat analysis revealed that approximately 35% of the macroscopic PMD specimens could be classified as biparental, while the remainder were ABM. We performed a DNA methylation analysis using bisulfite pyrosequencing of 15 placenta-specific imprinted differentially methylated regions (DMRs) and 36 ubiquitous imprinted DMRs. As expected, most DMRs in the macroscopic PMD specimens with ABM exhibited the paternal epigenotype. Importantly, the biparental macroscopic PMD specimens exhibited frequent aberrant hypomethylation at seven of the placenta-specific DMRs. Allelic expression analysis using single-nucleotide polymorphisms revealed that five imprinted genes associated with these aberrantly hypomethylated DMRs were biallelically expressed. Frequent aberrant hypomethylation was observed at five ubiquitous DMRs, including GRB10 but not ICR2 or ICR1, which regulate the expression of CDKN1C and IGF2, respectively. Whole-exome sequencing performed on four biparental macroscopic PMD specimens did not reveal any pathological genetic abnormalities. Clinical and molecular analyses of babies born from pregnancies with PMD revealed four cases with BWS, each exhibiting different molecular characteristics, and those between BWS and PMD specimens were not always the same.

CONCLUSION

These data clarify the prevalence of biparental PMD and ABM-PMD and strongly implicate hypomethylation of DMRs in the pathogenesis of biparental PMD, particularly placenta-specific DMRs and the ubiquitous GRB10, but not ICR2 or ICR1. Aberrant hypomethylation of DMRs was partial, indicating that it occurs after fertilization. PMD is an imprinting disorder, and it may be a missing link between imprinting disorders and placental disorders incompatible with life, such as complete hydatidiform moles and partial hydatidiform moles.

Preimplantation chromosomal mosaics, chimaeras and confined placental mosaicism

Some human preimplantation embryos are chromosomally mosaic. For technical reasons, estimates of the overall frequency vary widely from <15 to >90% and the true frequency remains unknown. Aneuploid/diploid and aneuploid/aneuploid mosaics typically arise during early cleavage stages before the embryonic genome is fully activated and when cell cycle checkpoints are not operating normally. Other mosaics include chaotic aneuploid mosaics and mixoploids, some of which arise by abnormal chromosome segregation at the first cleavage division. Chimaeras are similar to mosaics, in having two genetically distinct cell populations, but they arise from more than one zygote and occur less often. After implantation, the frequency of mosaic embryos declines to about 2% and most are trisomic/diploid mosaics, with trisomic cells confined to the placenta. Thus, few babies are born with chromosomal mosaicism. This review discusses the origin of different types of chromosomal mosaics and chimaeras; their fate and the relationship between preimplantation chromosomal mosaicism and confined placental mosaicism in human conceptuses and animal models. Abnormal cells in mosaic embryos may be depleted by cell death, other types of cell selection or cell correction but the most severely affected mosaic embryos probably die. Trisomic cells could become restricted to placental lineages if cell selection or correction is less effective in placental lineages and/or they are preferentially allocated to a placental lineage. However, the relationship between preimplantation mosaicism and confined placental mosaicism may be complex because the specific chromosome(s) involved will influence whether chromosomally abnormal cells survive predominately in the placental trophoblast and/or placental mesenchyme.

Lay summary

Human cells normally have 23 pairs of chromosomes, which carry the genes. During the first few days of development, some human embryos are chromosomal mosaics. These mosaic embryos have both normal cells and cells with an abnormal number of chromosomes, which arise from the same fertilised egg. (More rarely, the different cell populations arise from more than one fertilised egg and these embryos are called chimaeras.) If chromosomally abnormal cells survive to term, they could cause birth defects. However, few abnormal cells survive and those that do are usually confined to the placenta, where they are less likely to cause harm. It is not yet understood how this restriction occurs but the type of chromosomal abnormality influences which placental tissues are affected. This review discusses the origin of different types of chromosomally abnormal cells, their fate and how they might become confined to the placenta in humans and animal models.

Prenatal Diagnosis of Placental Mesenchymal Dysplasia with 46, X, Isochromosome Xq/45, X Mosaicism

Placental mesenchymal dysplasia is an uncommon vascular anomaly of the placenta with characteristics of placentomegaly and multicystic appearance and with or without association with fetal chromosomal anomaly. We present a unique placental mesenchymal dysplasia patient with amniotic fluid karyotyping as 46, X, iso(X) (q10). Detailed molecular testing of the amniotic fluid, fetal cord blood, non-dysplastic placenta and dysplastic placenta was conducted after termination of pregnancy, from which we proved biparental/androgenetic (46, X, i(X) (q10)/45, X) mosaicism in different gestational tissues. A high portion of androgenetic cells in dysplastic placenta (74.2%) and near 100% of biparental cells in the fetus’s blood and amniotic fluid were revealed. Delicate mosaic analyses were performed, and possible pathogenesis and embryogenesis of this case were drawn up.

A Challenging Diagnosis: Placental Mesenchymal Dysplasia—Literature Review and Case Report

We describe a 22-year-old woman (2-gravid) case who was referred to our clinic at 18 weeks of gestation for a placenta with vesicular lesions discovered on prenatal examination routine. An ultrasound exam at 31 weeks of gestation showed numerous vesicular lesions, which gradually augmented as the pregnancy advanced. A live normal-appearing fetus was confirmed by intrauterine growth restriction (IUGR). The maternal serum β-human chorionic gonadotropin level remained in normal ranges. At some point, a multidisciplinary medical consensus considered the termination of the pregnancy, but the patient refused to comply. At 33 weeks of gestation, preterm premature rupture of membranes (pPROM) occurred, and she spontaneously delivered a 1600 g healthy female baby with a good long-term outcome. Placental mesenchymal dysplasia (PMD) was retrospectively diagnosed after confronting the data from ultrasound, chorionic villus sampling (CVS), amniocentesis, pathological examination, and immunohistochemical stain. The lack of sufficient reports of PMD determines doctors to be cautious and reserved, approaching these cases more radically than necessary. We reviewed this disease and searched for all cases of PMD associated with healthy, live newborns.

Advances in the diagnosis and early management of gestational trophoblastic disease

Gestational trophoblastic disease describes a group of rare pregnancy related disorders that span a spectrum of premalignant and malignant conditions. Hydatidiform mole (also termed molar pregnancy) is the most common form of this disease. Hydatidiform mole describes an abnormal conceptus containing two copies of the paternal genome, which is classified as partial when the maternal genome is present or complete when the maternal genome is absent. Hydatidiform mole typically presents in the first trimester with irregular vaginal bleeding and can be suspected on ultrasound but confirmation requires histopathological evaluation of the products of conception. Most molar pregnancies resolve without treatment after uterine evacuation, but occasionally the disease persists and develops into gestational trophoblastic neoplasia. Close monitoring of women after molar pregnancy, with regular measurement of human chorionic gonadotrophin concentrations, allows for early detection of malignancy. Given the rarity of the disease, clinical management and treatment is best provided in specialist centres where very high cure rates are achievable. This review looks at advances in the diagnosis and early management of gestational trophoblastic disease and highlights updates to disease classification and clinical guidelines. Use of molecular genotyping for improved diagnostic accuracy and risk stratification is reviewed and future biomarkers for the earlier detection of malignancy are considered.

Placental mesenchymal dysplasia: What every radiologist needs to know

Placental mesenchymal dysplasia (PMD) is an uncommon vascular anomaly of the placenta characterized by placentomegaly with multicystic placental lesion on ultrasonography and mesenchymal stem villous hyperplasia on histopathology. Placental mesenchymal dysplasia should be considered in the differential diagnosis of cases of multicystic placental lesion such as molar pregnancy, chorioangioma, subchorionic hematoma, and spontaneous abortion with hydropic placental changes. However, lack of high-velocity signals inside the lesion and a normal karyotype favor a diagnosis of PMD. PMD must be differentiated from gestational trophoblastic disease because management and outcomes differ. We report the case of an 18-year-old female at 15 weeks of gestation with sonographic findings suggestive of placental mesenchymal dysplasia. The diagnosis was confirmed on histopathology.

Hearing Impairment with Monoallelic GJB2 Variants: A GJB2 Cause or Non-GJB2 Cause?

Recessive variants in GJB2 are the most common genetic cause of sensorineural hearing impairment. However, in many patients, only one variant in the GJB2 coding region is identified using conventional sequencing strategy (eg, Sanger sequencing), resulting in nonconfirmative diagnosis. Conceivably, there might be other unidentified pathogenic variants in the noncoding region of GJB2 or other deafness-causing genes in these patients. To address this, a next-generation sequencing-based diagnostic panel targeting the entire GJB2 gene and the coding regions of 158 other known deafness-causing genes was designed and applied to 95 patients with nonsyndromic sensorineural hearing impairment (including 81 Han Taiwanese and 14 Mongolian patients) in whom only a single GJB2 variant had been detected using conventional Sanger sequencing. The panel confirmed the genetic diagnosis in 24 patients (25.3%). Twenty-two of them had causative variants in several deafness-causing genes other than GJB2, including MYO15A, MYO7A, TECTA, POU4F3, KCNQ4, SLC26A4, OTOF, MT-RNR1, MITF, WFS1, and USH2A. The other two patients had causative variants in GJB2, including a Taiwanese patient with a mosaic maternal uniparental disomy c.235delC variant (approximately 69% mosaicism) and a Mongolian patient with compound heterozygous c.35dupG and c.35delG variants, which occurred at the same site. This study demonstrates the utility of next-generation sequencing in clarifying the genetic diagnosis of hearing-impaired patients with nonconfirmative GJB2 genotypes on conventional genetic examinations.

Variants in Maternal Effect Genes and Relaxed Imprinting Control in a Special Placental Mesenchymal Dysplasia Case with Mild Trophoblast Hyperplasia

Placental mesenchymal dysplasia (PMD) and partial hydatidiform mole (PHM) placentas share similar characteristics, such as placental overgrowth and grape-like placental tissues. Distinguishing PMD from PHM is critical because the former can result in normal birth, while the latter diagnosis will lead to artificial abortion. Aneuploidy and altered dosage of imprinted gene expression are implicated in the pathogenesis of PHM and also some of the PMD cases. Diandric triploidy is the main cause of PHM, whereas mosaic diploid androgenetic cells in the placental tissue have been associated with the formation of PMD. Here, we report a very special PMD case also presenting with trophoblast hyperplasia phenotype, which is a hallmark of PHM. This PMD placenta has a normal biparental diploid karyotype and is functionally sufficient to support normal fetal growth. We took advantage of this unique case to further dissected the potential common etiology between these two diseases. We show that the differentially methylated region (DMR) at NESP55, a secondary DMR residing in the GNAS locus, is significantly hypermethylated in the PMD placenta. Furthermore, we found heterozygous mutations in NLRP2 and homozygous variants in NLRP7 in the mother’s genome. NLRP2 and NLRP7 are known maternal effect genes, and their mutation in pregnant females affects fetal development. The variants/mutations in both genes have been associated with imprinting defects in mole formation and potentially contributed to the mild abnormal imprinting observed in this case. Finally, we identified heterozygous mutations in the X-linked ATRX gene, a known maternal–zygotic imprinting regulator in the patient. Overall, our study demonstrates that PMD and PHM may share overlapping etiologies with the defective/relaxed dosage control of imprinted genes, representing two extreme ends of a spectrum.

Refined diagnosis of hydatidiform moles with p57 immunohistochemistry and molecular genotyping: updated analysis of a prospective series of 2217 cases

Immunohistochemical analysis of p57 expression and molecular genotyping accurately subclassify molar specimens into complete hydatidiform mole (CHM) and partial hydatidiform mole (PHM) and distinguish these from nonmolar specimens. Characteristics of a prospective series of potentially molar specimens analyzed in a large gynecologic pathology practice are summarized. Of 2217 cases (2160 uterine, 57 ectopic), 2080 (94%) were successfully classified: 571 CHMs (570 uterine, 1 ectopic), 498 PHMs (497 uterine, 1 ectopic), 900 nonmolar (including 147 trisomies, 19 digynic triploids, and 4 donor egg conceptions), and 56 androgenetic/biparental mosaics; 137 were complex or unsatisfactory and not definitively classified. CHMs dominated in patients aged < 21 and >45 years and were the only kind of molar conception found in the latter group. Of 564 successfully immunostained CHMs, 563 (99.8%) were p57-negative (1 p57-positive [retained maternal chromosome 11] androgenetic by genotyping). Of 153 genotyped CHMs, 148 (96.7%) were androgenetic (85% monospermic) and 5 were biparental, the latter likely familial biparental hydatidiform moles. Of 486 successfully immunostained PHMs, 481 (99%) were p57-positive (3 p57-negative [loss of maternal chromosome 11], 2 unknown mechanism). Of 497 genotyped PHMs, 484 (97%) were diandric triploid (99% dispermic) and 13 were triandric tetraploid (all at least dispermic). Of 56 androgenetic/biparental mosaics, 37 had a p57-negative complete molar component (16 confirmed as androgenetic by genotyping). p57 expression is highly correlated with genotyping, serving as a reliable marker for CHMs, and identifies molar components and androgenetic cell lines in mosaic conceptions. Correlation of morphology, p57 expression, genotyping data, and history are required to recognize familial biparental hydatidiform moles and donor egg conceptions, as the former can be misclassified as nonmolar and the latter can be misclassified as dispermic CHM on the basis of isolated genotyping results.

Association of Placental Mesenchymal Dysplasia With a Live Female Fetus and Complete Hydatidiform Mole: Report of a Challenging Case Confirmed by Molecular Genotyping Analysis

Placental mesenchymal dysplasia (PMD) and complete hydatidiform mole (CHM) with a coexisting fetus are 2 rare placental abnormalities characterized by lacunar placenta and presence of an embryo on ultrasound examination. We report the case of a 34-yr-old woman referred at 32.6 weeks of gestation because of a multicystic placenta. A caesarean section was performed at 39.1 weeks of gestation giving birth to a 2905 g normal female infant. Pathological examination revealed macroscopic and microscopic morphological, and immunohistological features of PMD in the main placenta, and features of CHM in a separate placental mass. Fluorescent in situ hybridization and molecular genotyping analyses showed diandric diploidy in the CHM component and androgenetic/biparental mosaicism in the PMD component, confirming the association of PMD and CHM with a live infant. There was no progression to gestational trophoblastic neoplasia during follow-up for the mother, or any sign of Beckwith-Wiedemann syndrome or hepatic tumor in the child.

Genome-wide abnormalities in embryos: Origins and clinical consequences

Ploidy or genome-wide chromosomal anomalies such as triploidy, diploid/triploid mixoploidy, chimerism, and genome-wide uniparental disomy are the cause of molar pregnancies, embryonic lethality, and developmental disorders. While triploidy and genome-wide uniparental disomy can be ascribed to fertilization or meiotic errors, the mechanisms causing mixoploidy and chimerism remain shrouded in mystery. Different models have been proposed, but all remain hypothetical and controversial, are deduced from the developmental persistent genomic constitutions present in the sample studied and lack direct evidence. New single-cell genomic methodologies, such as single-cell genome-wide haplotyping, provide an extended view of the constitution of normal and abnormal embryos and have further pinpointed the existence of mixoploidy in cleavage-stage embryos. Based on those recent findings, we suggest that genome-wide anomalies, which persist in fetuses and patients, can for a large majority be explained by a noncanonical first zygotic cleavage event, during which maternal and paternal genomes in a single zygote, segregate to different blastomeres. This process, termed heterogoneic division, provides an overarching theoretical basis for the different presentations of mixoploidy and chimerism.

Recurrent GTD and GTD coexisting with normal twin pregnancy

Hydatidiform mole (HM) affects around 1/1000 pregnancies, and in such cases the recurrence risk is around 1%, being greater for those with complete HM (CHM). Whilst most cases appear sporadic with unknown mechanisms, there is a distinct subgroup of patients who suffer recurrent pregnancy loss, including multiple recurrent CHM (familial recurrent biparental HM syndrome). The majority of these cases are related to maternal genetic mutations in genes related to the control of imprinting, specifically NALP7 and KHDC3L. Oocyte donation is an effective treatment allowing these patients to have successful pregnancies. Approximately 1 in 50,000 pregnancies are complicated by twin pregnancy comprising normal foetus and HM, the majority of reported cases being CHM. Such pregnancies are at significantly increased risk of complications, including pregnancy loss, early-onset preeclampsia and severe preterm delivery, but when managed conservatively the delivery of a liveborn healthy infant occurs in around one-third of cases. Regardless of management, the risk of persistent GTD in such cases appears similar to that following singleton CHM. Rarely, other conditions mimic prenatal ultrasound appearances of twin pregnancy with HM, CHM mosaicism and placental mesenchymal dysplasia, both of which have distinctive histological and genetic features.

Natural human chimeras: A review

The term chimera has been borrowed from Greek mythology and has a long history of use in biology and genetics. A chimera is an organism whose cells are derived from two or more zygotes. Recipients of tissue and organ transplants are artificial chimeras. This review concerns natural human chimeras. The first human chimera was reported in 1953. Natural chimeras can arise in various ways. Fetal and maternal cells can cross the placental barrier so that both mother and child may become microchimeras. Two zygotes can fuse together during an early embryonic stage to form a fusion chimera. Most chimeras remain undetected, especially if both zygotes are of the same genetic sex. Many are discovered accidently, for example, during a routine blood group test. Even sex-discordant chimeras can have a normal male or female phenotype. Only 28 of the 50 individuals with a 46,XX/46,XY karyotype were either true hermaphrodites or had ambiguous genitalia. Blood chimeras are formed by blood transfusion between dizygotic twins via the shared placenta and are more common than was once assumed. In marmoset monkey twins the exchange via the placenta is not limited to blood but can involve other tissues, including germ cells. To date there are no examples in humans of twin chimeras involving germ cells. If human chimeras are more common than hitherto thought there could be many medical, social, forensic, and legal implications. More multidisciplinary research is required for a better understanding of this fascinating subject.

p57-discordant villi in hydropic products of conception: a clinicopathological study of 70 cases

p57 immunostaining is performed on hydropic products of conception to diagnose hydatidiform moles (HMs), which can progress to gestational trophoblastic neoplasia. Partial hydatidiform mole (PHM) and hydropic abortion (HA) display positive staining in stromal and cytotrophoblastic cells, whereas complete hydatidiform mole (CHM) is characterized by loss of p57 expression in both cell types. In some cases, an aberrant pattern is observed, called discordant p57 expression, with positive cytotrophoblast staining and negative stromal staining, or vice versa. The aim of this study was to describe the clinical, biological, and pathological characteristics of p57-discordant villi (p57DV) and other associated populations in cases of divergent p57 expression and to compare the evolutions of p57DV-associated and classic CHMs. Seventy cases of p57DV diagnosed by referent pathologists were divided into two groups, G1: p57DV ± non-CHM component (n = 22) and G2: p57DV + CHM component (n = 48). p57DV morphology was similar in the two groups. Observation of more than two populations and hybrid villi on p57 immunostaining were significantly more frequent in G2. The clinical, ultrasound, and biological presentations of p57DV-associated and classic CHMs were similar. The initial pathological diagnosis was more frequently incorrect, missing the CHM component, for the p57DV-associated CHMs. Molecular genotyping was informative in seven cases and identified as androgenetic/biparental mosaicism in four cases. These results show that p57DV are a diagnostic challenge for pathologists and that most are associated with a CHM component. However, the clinical management of p57DV-associated CHMs should be the same as that of classic CHMs.

A case of a parthenogenetic 46,XX/46,XY chimera presenting ambiguous genitalia

Sex-chromosome discordant chimerism (XX/XY chimerism) is a rare chromosomal disorder in humans. We report a boy with ambiguous genitalia and hypospadias, showing 46,XY[26]/46,XX[4] in peripheral blood cells. To clarify the mechanism of how this chimerism took place, we carried out whole-genome genotyping using a SNP array and microsatellite analysis. The B-allele frequency of the SNP array showed a mixture of three and five allele combinations, which excluded mosaicism but not chimerism, and suggested the fusion of two embryos or a shared parental haplotype between the two parental cells. All microsatellite markers showed a single maternal allele. From these results, we concluded that this XX/XY chimera is composed of two different paternal alleles and a single duplicated maternal genome. This XX/XY chimera likely arose from a diploid maternal cell that was formed via endoduplication of the maternal genome just before fertilization, being fertilized with both X and Y sperm.

Sperm DNA damage causes genomic instability in early embryonic development

Genomic instability is common in human embryos, but the underlying causes are largely unknown. Here, we examined the consequences of sperm DNA damage on the embryonic genome by single-cell whole-genome sequencing of individual blastomeres from bovine embryos produced with sperm damaged by γ-radiation. Sperm DNA damage primarily leads to fragmentation of the paternal chromosomes followed by random distribution of the chromosomal fragments over the two sister cells in the first cell division. An unexpected secondary effect of sperm DNA damage is the induction of direct unequal cleavages, which include the poorly understood heterogoneic cell divisions. As a result, chaotic mosaicism is common in embryos derived from fertilizations with damaged sperm. The mosaic aneuploidies, uniparental disomies, and de novo structural variation induced by sperm DNA damage may compromise fertility and lead to rare congenital disorders when embryos escape developmental arrest.

Placental mesenchymal dysplasia with a good outcome: A case report

Placental mesenchymal dysplasia (PMD), characterized by an enlarged and thickened placenta with multiple hypoechoic cystic spaces, frequently leads to a poor infantile/fetal outcome. Here, we describe a case of PMD involving an infant delivered at term with a good outcome. The fetus was male, and the proportion of the PMD lesion to the entire placenta remained constant: the PMD lesion did not enlarge. Given what is known about the pathogenesis of PMD with its association with vascular endothelial growth factor-D (VEGF-D) encoded by an X-linked gene and androgenetic/biparental mosaicism, which is consistent with female dominancy and a poor outcome, we suggest that a male sex of the fetus and non-progressing PMD may have been associated with this good outcome.

Mosaic paternal haploidy in a patient with pancreatoblastoma and Beckwith-Wiedemann spectrum

Pancreatoblastoma is a rare type of pancreatic cancer in children. Here, we describe a case in which Beckwith-Wiedemann syndrome (BWS) was first suspected because of placental mesenchymal dysplasia. Although the baby did not show the stigmata characteristic of BWS or abnormal peripheral blood methylation, she developed a massive pancreatoblastoma 2 months later. She survived after partial excision of the tumor and chemotherapy. The methylation pattern of the pancreatoblastoma tissue was typical of BWS. Single nucleotide polymorphism (SNP) array analyzes revealed that the pancreatoblastoma tissue had genome-wide loss of maternal alleles. Peripheral blood and nontumor pancreatic tissue showed normal biparental genomic contribution. Interphase fluorescence in situ hybridization analysis with centromeric probes for chromosomes 2 and 11 revealed haploid pancreatoblastoma cells, whereas the placental mesenchymal dysplasia tissue and nontumor pancreas tissue showed diploidy. SNP genotype analysis suggested the presence of mosaicism with the pancreatoblastoma tissue having a different paternal haplotype than that of the peripheral blood and nontumor pancreatic tissue. We report for the first time mosaic paternal haploidy associated with pancreatoblastoma. Babies with placental mesenchymal dysplasia, even those without a definitive diagnosis of BWS, need to be closely followed for the occurrence of embryonic tumors.

A case report of placental mesenchymal dysplasia: A rare case of a genetically normal fetus with severe intrauterine growth restriction

RATIONALE

We report a rare case of a pregnant woman with placental mesenchymal dysplasia (PMD) and intrauterine growth restriction (IUGR) with a genetically normal fetus.

PATIENT CONCERNS

A 42-year-old woman Gravida I, Para I with pre-existent uncontrolled hypertension and uterine polyfibromatosis present at 30 weeks of gestation for diminished fetal activity during the last 2 days.

DIAGNOSIS

Placental mesenchymal dysplasia associated with intrauterine growth restriction, hypertension, and uterine polyfibromatosis.

INTERVENTION

A live male infant was delivered by emergency caesarean section.

OUTCOMES

The infant, weighing 700 g, died 4 days after birth due to a massive intracerebral hemorrhage.

LESSONS

A careful examination should be done at every ultrasound in case of a fetus with IUGR to exclude some rare cases of placental pathologies. PMD can be a rare cause of IUGR with a genetically normal fetus.

Could a chimeric condition be responsible for unexpected genetic syndromes? The role of the single nucleotide polymorphism-array analysis

In this paper, is reported the identification of two chimeric patients, a rare finding if sexual abnormalities are absent. However, their chimeric condition is responsible at least for the Silver-Russell phenotype observed in one of the two patients. By single nucleotide polymorphism-array analyses, it was possible to clearly define the mechanism responsible for this unusual finding, underlining the importance of this technique in bringing out the perhaps submerged world of chimeras.

[Placental mesenchymal dysplasia]

OBJECTIVE

To carry out a clinical and morphological analysis of 6 cases of placental mesenchymal dysplasia (PMD) that is not associated with Beckwith-Wiedemann syndrome.

MATERIAL AND METHODS

Medical records, placental macroscopic and microscopic changes, histochemical (MSB staining) and immunohistochemical studies of placental tissue with antibodies against p57, CD34, smooth muscle actin, desmin, and Ki-67 were analyzed.

RESULTS

Vascular anomalies in the chorionic plate and stem villi, the increased size and edema of the stem villi during normal formation of the terminal branches of the villous tree, the lack of proliferation of villous trophoblast were the typical signs of PMD and were noted in all cases. Comparison of the results of ultrasonography with the morphological pattern of the disease suggested that there were ultrasound signs that were typical of PMD. The characteristics of the course and outcomes of pregnancy in PMD were given. The features of morphological changes in the presence of PMD concurrent with preeclampsia were found. Significant variability in p57 expression in PMD was shown and variants of changes given. There were no substantial features of the expression of desmin and smooth muscle actin in PMD.

CONCLUSION

MDP has typical morphological and ultrasound signs. The significant variability in the levels of chorionic gonadotropin and alpha-fetoprotein and in the expression of p57 does not allow their use in the differential diagnosis of PMD. The high incidence of thrombotic events in the intervillous space and fetal vessels, as well as intrauterine growth restriction, intrauterine hypoxia, and an impaired neonatal adaptation period in PMD should be taken into account when determining the management tactics for female patients and newborns.

Hydatidiform Moles: Ancillary Techniques to Refine Diagnosis

Context.—

Distinction of hydatidiform moles from nonmolar specimens and subclassification of hydatidiform moles as complete hydatidiform mole versus partial hydatidiform mole are important for clinical practice and investigational studies. Risk of persistent gestational trophoblastic disease and clinical management differ for these entities. Diagnosis based on morphology is subject to interobserver variability and remains problematic, even for experienced gynecologic pathologists.

Objectives.—

To explain how ancillary techniques target the unique genetic features of hydatidiform moles to establish diagnostic truth, highlight the issue of diagnostic reproducibility and importance of diagnostic accuracy, and illustrate use of p57 immunohistochemistry and polymerase chain reaction–based DNA genotyping for diagnosis.

Data Sources.—

Sources are the author's 10-year experience using ancillary techniques for the evaluation of potentially molar specimens in a large gynecologic pathology practice and the literature.

Conclusions.—

The unique genetics of complete hydatidiform moles (purely androgenetic), partial hydatidiform moles (diandric triploid), and nonmolar specimens (biparental, with allelic balance) allow for certain techniques, including immunohistochemical analysis of p57 expression (a paternally imprinted, maternally expressed gene) and genotyping, to refine diagnoses of hydatidiform moles. Although p57 immunostaining alone can identify complete hydatidiform moles, which lack p57 expression because of a lack of maternal DNA, this analysis does not distinguish partial hydatidiform moles from nonmolar specimens because both express p57 because of the presence of maternal DNA. Genotyping, which compares villous and decidual DNA patterns to determine the parental source and ratios of polymorphic alleles, distinguishes purely androgenetic complete hydatidiform moles from diandric triploid partial hydatidiform moles, and both of these from biparental nonmolar specimens. An algorithmic approach to diagnosis using these techniques is advocated.

Corpus Callosum Abnormalities and Short Femurs in Beckwith-Wiedemann Syndrome: A Report of Two Fetal Cases

INTRODUCTION

Beckwith-Wiedemann syndrome (BWS) is the most common overgrowth syndrome. Clinical features are highly variable, including occasional posterior fossa malformations but no femoral shortening.

CASE REPORT

We report two fetuses with BWS associated with short femurs and corpus callosum hypoplasia. Case 2 was growth restricted. BWS was confirmed by molecular studies showing a loss of methylation at ICR2 at 11p15 chromosomic region in case 1 and a gain of methylation at ICR1 and a loss of methylation at ICR2 locus in case 2.

CONCLUSION

Although the phenotype and the genotype of BWS is now well-known, the presence of corpus callosum abnormalities and short femurs expand the phenotypic spectrum of the disorder.

Biparental/androgenetic mosaicism in a male with features of overgrowth and placental mesenchymal dysplasia

Biparental/androgenetic mosaicism is a rarely diagnosed condition in humans. It is typically ascertained prenatally on the basis of placental mesenchymal dysplasia. Fetal outcome can range from demise due to intrauterine growth retardation to term delivery. Most of the published cases of liveborns represent females that are either completely normal or have features of Beckwith-Wiedemann syndrome. Only two healthy liveborn males with mosaicism detected in the placenta have been described to date. Here, we report another liveborn male with hepatic mesenchymal hamartoma, soft tissue overgrowth on his right fifth toe, hemangiomas over his chest, right buttock and foot, anemia, thrombocytopenia and congenital hypothyroidism with biparental/androgenetic mosaicism detected in the toe mass in addition to the placenta. This new case adds to the existing literature of individuals with biparental/androgenetic mosaicism and expands the range of clinical presentations that may be seen in male patients with this condition. This study also illustrates the important use of single-nucleotide polymorphism microarray in conjunction with short-tandem repeat analysis on affected tissue to provide a diagnosis for patients with features of overgrowth and prior, non-diagnostic, genetic analyses of their peripheral blood.

Genetic and Epigenetic Control of CDKN1C Expression: Importance in Cell Commitment and Differentiation, Tissue Homeostasis and Human Diseases

The CDKN1C gene encodes the p57^Kip2 protein which has been identified as the third member of the CIP/Kip family, also including p27^Kip1 and p21^Cip1. In analogy with these proteins, p57^Kip2 is able to bind tightly and inhibit cyclin/cyclin-dependent kinase complexes and, in turn, modulate cell division cycle progression. For a long time, the main function of p57^Kip2 has been associated only to correct embryogenesis, since CDKN1C-ablated mice are not vital. Accordingly, it has been demonstrated that CDKN1C alterations cause three human hereditary syndromes, characterized by altered growth rate. Subsequently, the p57^Kip2 role in several cell phenotypes has been clearly assessed as well as its down-regulation in human cancers. CDKN1C lies in a genetic locus, 11p15.5, characterized by a remarkable regional imprinting that results in the transcription of only the maternal allele. The control of CDKN1C transcription is also linked to additional mechanisms, including DNA methylation and specific histone methylation/acetylation. Finally, long non-coding RNAs and miRNAs appear to play important roles in controlling p57^Kip2 levels. This review mostly represents an appraisal of the available data regarding the control of CDKN1C gene expression. In addition, the structure and function of p57^Kip2 protein are briefly described and correlated to human physiology and diseases.

Placental Pathology in Placental Mesenchymal Dysplasia with 13q12.11 Deletion and a 25-Week Gestation Female Infant

Patient: —

Final Diagnosis: Placental mesenchymal dysplasia

Symptoms: Premature rupture of membranes

Medication:—

Clinical Procedure: Amniocentesis

Specialty: Obstetrics and Gynecology

Diffuse Chorangiomatosis as a Cause of Cardiomegaly, Microangiopathic Hemolytic Anemia and Thrombocytopenia in a Newborn

INTRODUCTION

The hallmark of diffuse chorangiomatosis is capillary dysvasculogenesis, diffusely involving the placenta. It can cause massive placental enlargement and may have adverse fetal effects.

CASE REPORT

A 32 weeks gestation male infant was born via cesarean section and had a placenta weighing 900 g. There was diffuse vascular proliferation involving the stem villi and intermediate villi. Short Nucleotide Polymorphism (SNP) microarray analysis of the placenta showed no biparental mosaicism or loss of heterozygosity, ruling out placental mesenchymal dysplasia. The infant also had cardiomegaly, microangiopathic hemolytic anemia and thrombocytopenia which spontaneously improved over time.

CONCLUSION

Diffuse chorangiomatosis can be associated with hemolysis, thrombocytopenia and cardiomegaly in the newborn. However, once delivered, these findings can spontaneously resolve over time.

Placental Mesenchymal Dysplasia With Normal Fetus: A Rare Case Report

Placental mesenchymal dysplasia (PMD) is a rare benign placental abnormality. It is characterized by hydropic degeneration of stem villi, placentomegaly, and increased maternal serum alpha-fetoprotein (AFP). It can be associated with different congenital abnormalities, karyotype abnormalities, and feto-maternal morbidities. It is difficult to differentiate PMDfrom partial mole, complete mole with twin pregnancy in ultrasound, and in macroscopic examination. The current paper presentsa rare case of placental mesenchymal dysplasia in a young primigravida mother who delivered a normal fetus withnormal karyotype.

Late diagnosis of hepatic mesenchymal hamartoma and placental mesenchymal dysplasia

Placental mesenchymal dysplasia (PMD) is a rare condition characterised by placental enlargement, oedematous villi and multiple anechoic cysts. Hepatic mesenchymal hamartoma (HMH) is a benign proliferation of mesenchymal tissue, commonly seen in infants below the age of 2. We report the case of a 28 years old female who was noted to have a fetus with a well-circumscribed cyst on the liver, suggestive of HMH and a large, thickened placenta, with multiple anechoic cysts, consistent with PMD during the third trimester. There were no other structural abnormalities and at 38 weeks she underwent an induction of labour with normal vaginal delivery of a live female infant. While the aetiology is poorly understood, the increased incidence of HMH with PMD and the morphological similarities of the changes seen in both the placenta and liver, suggests a possible common developmental mechanism. There are only 12 other cases of this concurrent pathology in the literature and only one of these had resulted in a term delivery, and ours is the second one to date.

Zygotes segregate entire parental genomes in distinct blastomere lineages causing cleavage-stage chimerism and mixoploidy

Dramatic genome dynamics, such as chromosome instability, contribute to the remarkable genomic heterogeneity among the blastomeres comprising a single embryo during human preimplantation development. This heterogeneity, when compatible with life, manifests as constitutional mosaicism, chimerism, and mixoploidy in live-born individuals. Chimerism and mixoploidy are defined by the presence of cell lineages with different parental genomes or different ploidy states in a single individual, respectively. Our knowledge of their mechanistic origin results from indirect observations, often when the cell lineages have been subject to rigorous selective pressure during development. Here, we applied haplarithmisis to infer the haplotypes and the copy number of parental genomes in 116 single blastomeres comprising entire preimplantation bovine embryos (n = 23) following in vitro fertilization. We not only demonstrate that chromosome instability is conserved between bovine and human cleavage embryos, but we also discovered that zygotes can spontaneously segregate entire parental genomes into different cell lineages during the first post-zygotic cleavage division. Parental genome segregation was not exclusively triggered by abnormal fertilizations leading to triploid zygotes, but also normally fertilized zygotes can spontaneously segregate entire parental genomes into different cell lineages during cleavage of the zygote. We coin the term "heterogoneic division" to indicate the events leading to noncanonical zygotic cytokinesis, segregating the parental genomes into distinct cell lineages. Persistence of those cell lines during development is a likely cause of chimerism and mixoploidy in mammals.

Fetal Thrombotic Vasculopathy: Perinatal Stroke, Growth Restriction, and Other Sequelae

Clots in the fetal circulation of the placenta may occlude or narrow the lumens of fetal vessels sufficiently to diminish the placental oxygen and nutritional exchange, causing significant reduction in placental function. When extensive, growth restriction, neonatal encephalopathy, and stillbirth may occur. Propagation of clots in other organs, such as brain, kidney, and liver, may affect the function of these organs, resulting in infarcts and neonatal stroke. This article presents an account of the placental pathology and clinical sequelae of this condition, called fetal thrombotic vasculopathy.

Paternal Hemizygosity in 11p15 in Mole-like Conceptuses: Two Case Reports

Hydatidiform mole is an abnormal human pregnancy characterized by the fetus being absent or nonviable, and the chorionic villi being vesicular and with trophoblastic hyperplasia. Most often, the mole phenotype is seen in conceptuses with an excess of paternally inherited genome set(s) relative to maternally inherited genome set(s), suggesting that the phenotype is caused by an excess of genome with a paternal imprinting pattern. However, it is unknown if correct parental origin of every imprinted gene is crucial for normal early differentiation or if abnormal parental imprinting of only one, or some, gene(s) can cause the mole phenotype.Two conceptuses included in the Danish Mole Project stood out since they presented with vesicular chorionic villi and without signs of fetal differentiation, and had apparently biparental diploid genomes, and no mutations in NLRP7 or KHDC3L were detected in the mothers. These conceptuses were subjected to a centralized histopathological revision and their genetic complements were scrutinized using fluorescence in situ hybridization, and DNA-marker and array comparative genomic hybridization analyses. Both conceptuses showed dysmorphic chorionic villi with some similarities to hydatidiform moles; however, no definite florid trophoblast hyperplasia was observed. Both conceptuses showed paternal hemizygosity of 11pter-11p15.4, most likely in nonmosaic state.Our findings suggest that the product of one (or a few) maternally expressed gene(s) on the tip of chromosome 11 is necessary for normal early embryonic differentiation. However, since the present two cases did not exhibit all features of hydatidiform moles, it is likely that abnormal parental imprinting of genes in other regions contribute to the phenotype of a hydatidiform mole.