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A case report of an omphalopagus heteropagus (parasitic) twin

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Abstract

Heteropagus twin refers to a type of conjoined twin in which an incomplete smaller (parasitic) twin is attached to and dependent upon an otherwise normal host twin. The majority of cases have complete or partial duplication of the pelvis and/or lower extremities. The case depicted herein is unusual in that only isolated case reports have described an attached amorphous mass without identifiable limbs.

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... The exact incidence is unknown but it is estimated to be less than 1 in 1 million births [1][2][3]. It refers to the type of conjoined twin in which tissues of an incompletely formed twin (parasite) are attached to and dependent upon a fully developed twin (autosite) [2][3][4]. ...
... The "fission" theory suggests incomplete separation of the embryo while the "fusion" theory proposes coalition of 2 originally distinct parts [2,5]. The most advanced theory postulates that it occurs due to vascular compromise in utero, leading to death and partial resorption of one of the twins [2,4]. ...
... Contents of parasitic twins we observed like presence of pelvis, genitalia, scrotum, anus and intestine, have also been previously reported [2,3,6]. Case 4, which was a mass without limbs, is rare but has been described as well [2,4,10,15]. ...
Article
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Heteropagus (parasitic) twin is a type of conjoined twinning in which a partially formed defective twin is attached to an otherwise normal twin. It is an extremely rare anomaly. In this paper, we describe five cases we encountered over the past 9 years. Except one, all presented early within a few days of birth. None of them shared an organ but two had bony/visceral connections. All surgeries were successful, and we only encountered wound complications. To the best of our knowledge this is the largest compilation of original cases in a parasitic twin report.
... Be it a staged or primary surgery, the importance of complete exploration and removal of parasitic viscera cannot be underrated, as reports of patients presenting with complications due to retained parasitic viscera are already there [14,22]. All cases in our series were dealt with in the neonatal period; though a mention of delayed repair for 10 cases was found in the literature [5,26,28,31,53,66,67,69,72]. One was an abandoned child [28], 2 were neglected [26,69] while others underwent delayed surgery either because of late presentation or as per institutional policy [5,31,53,68,72]. ...
... All cases in our series were dealt with in the neonatal period; though a mention of delayed repair for 10 cases was found in the literature [5,26,28,31,53,66,67,69,72]. One was an abandoned child [28], 2 were neglected [26,69] while others underwent delayed surgery either because of late presentation or as per institutional policy [5,31,53,68,72]. The authors are a proponent of surgery in the neonatal period. ...
Article
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Purpose Heteropagus twinning (HT) is a rare anomaly. Six new cases along with a systematic review are described. Methods Six cases of HT managed at two tertiary care teaching hospitals over the last 26 years are described. A PubMed search with words: Heteropagus AND/ OR parasitic twins from 2001 to 2021 hit 183 articles. 36 were added from non-PubMed sources. Finally, 120 cases including 114 from 69 articles and 6 new cases were analysed. Results Of the new cases, 2/6 had an antenatal diagnosis. Five were males. 4 autosites had omphaloceles. Split notochord and 2 parasites attached to a single autosite were encountered. 5/6 autosites survived. On systematic review, the most frequent variant seen was rachipagus (n = 50) followed by omphalopagus (n = 46). Limbs were reported in 75 cases. Congenital heart disease was seen in 17/120(14.2%) autosites. Omphalocele and meningomyelocele were the most common extracardiac anomalies in autosites. Weight along with the anatomy and position of heteropagus twins was a better determinant of the mode of delivery than weight alone. Mortality was reported in 12 cases. Conclusion Autosites in HT generally carry a good prognosis, however, final outcome depends mainly on associated major cardiac anomalies. Meticulous antenatal assessment and preoperative planning are of paramount importance. Level of evidence IV.
... It refers to the type of conjoined twin in which the 'Parasite' is incompletely formed twin, usually nonviable but survives in the host twin (the 'Autosite') which is fully developed. [1][2][3][4] The parasite has grossly recognizable fetal parts and is usually attached to the autosite by a soft tissue pedicle containing large blood vessels. [1][2][3] The site of attachment could be one of eight (thoracopagus, omphalopagus, craniopagus, cephalopagus, parapagus, ischiopagus, pyopagus or rachipagus). ...
... 1,2,8 The most advanced theory postulates that it occurs due to vascular compromise in utero, leading to death and partial resorption of one of the twins. 1,2,4 Since many aspects of this rare condition remain unknown, it has been recommended that all cases be reported 8 . Authors also discuss some peculiar findings from our report. ...
Article
Full-text available
Parasitic twins are an extremely rare form of asymmetrical conjoined monochorial monoamniotic twins where one of them has a mostly intact body that is able to survive and which is referred to as ‘autosite’, while the counterpart, referred to as ‘parasite’, is only rudimentarily developed being physically attached to and nourished by the other twin. Our case is a baby boy with Single Ventricle Heart defect with a thoraco-abdominal mass (epigastric heteropagus twin) attached to the anterior abdominal wall near the umbilicus with minimal visceral sharing. The twins had two external genitalia both in host and parasite micturating separately. After high risk surgery the parasite could be separated completely from the host and postoperative recovery was uneventful.
... In consequence, a sole embrionary structure is formed, but with a single yolk sac. The another theory mentioned was ischemic atrophy, in which the parasite twin is the result of an ischemic accident in the uterus, followed by the death and resorption of one of the foetuses [3,4]. ...
... An associated congenital cardiac malformations, has been described in autosites. However, a single-ventricle heart anomaly in the autosite has been reported in a very few cases [4][5][6][7]. The cardiac anomalies was found in the autosite index case. ...
Article
Heteropagus, or “parasitic,” twins are asymmetric conjoined twins, in which the host (autosite), is near normal and bears the parasite, which is totally dependent for growth on it. A parasitic twin who is attached to the epigastrium of the autosite is called as Epigastric heteropagus conjoined twins (EHTs) which are extremely rare. An associated congenital cardiac malformations, has been described in autosites. Here we report a rare case of epigastric heteropagus conjoined twins with cyanotic congenital heart disease (CHD) in the autosite.
... In consequence, a sole embrionary structure is formed, but with a single yolk sac. The DNA analysis always describes a homozygous karyotype [4,5]. ...
... The ischemic atrophy is another proposed theory, in which the parasite twin is the result of an ischemic accident in the uterus, followed by the death and resorption of one of the fetuses, this event allowing the parasite twin to attach to the normally developed fetus [4,5]. In order to properly manage this type of medical case, it is of paramount importance to establish prenatal integrity of the vital organs and the anatomical and functional distribution of the shared organs between twins, which allows these cases a favorable postoperative outcome compared to the surgical approach of the symmetric conjoined twins. ...
Article
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Twin pregnancies generally represent a high-risk pregnancy. However, monozygous twins are real challenges for obstetricians due to the complications that may occur. Among the particular cases of monozygous twins in the University Emergency Hospital of Bucharest, Department of Obstetrics and Gynecology, a monochorial monoamniotic pregnancy with conjoined twins has been described. These particular medical circumstances require a deeper understanding of the vascular anatomical particularities. An accurate diagnosis implies a most detailed description of the morphological dynamics of the fetuses with the study of the impact of the vascular anomaly on their development so that the maximum chances of survival and the best outcome for the viable fetus can be obtained. The diagnosis of the most frequently associated anomalies is also extremely important. Abbreviations: MRI = Magnetic resonance imaging
... Conjoined twin can be symmetrical or asymmetrical. The site and extent of twin fusion is extremely variable and the nomenclature is usually based on fused anatomical region as in this case the parasite was attached to the host in epigastric region so named as epigastric heteropagus [6,7]. In our case, parasitic twin had rudimentary limbs and external genitalia. ...
Article
Full-text available
Parasitic twining is a rare type of monozygotic monochorionic monoamniotic asymmetrical conjoined twin. We report a case of epigastric heteropagus twin. An ultrasound scan showed a defect of 1.5 cm in the epigastrium. CT showed soft tissue lobulated mass with fat and air components coming out of the epigastric defect. At operation rudimentary alimentary canal with no viscera, was found in the parasite. The parasite was easily separated from the host.
... The vascular communications in our patients were also less complex and vascular separation could be performed easily. Shared vital organs that are often observed in symmetrical conjoined twins are usually not seen in heteropagus twins [14]. Visceral connections between the heteropagus twins are also observed rarely. ...
Article
Full-text available
Heteropagus twins are an extremely rare condition and the term describes asymmetrical conjoined twins in which one twin (“autosite”) has a mostly intact body and the other twin (“parasite”) remains anatomically incomplete but is attached to and nourished by the other one. Autosites may show severe malformations themselves that are not associated with the twins’ fusion. Beyond the challenge of surgical separation further complex reconstructions may be necessary. In this case series we want to demonstrate that despite complex anatomic features, good functional (e.g. gastrointestinal, genitourinary and motoric) and aesthetic results can be achieved.
... Whilst conjoined twins are not uncommon, there are only case reports of heteropagus omphalopagus conjoined twins, and the terminology is worth clarifying. Using the definition of Rowena Spencer, this heteropagus twin (smaller, parasitic twin attached to, and dependent on, an otherwise normal host) [1] had a ventral omphalopagus union, which may include lower thorax but never sharing the heart. . [2] Most cases describing complete or partial duplication of the pelvis and/or lower extremities involve fusion of bowel lumen between twins [3]. ...
Article
Full-text available
This case report describes the management of a 27-year-old lady's partially auto-amputated heteropagus omphalopagus acardiac twin. This was a rare case that resulted in the parasitic twin's bowel being located extra-peritoneal but within the abdominal wall of the host twin.
... Omphalopagus heteropagus is an uncommon type of heteropagus, where the parasitic twin is attached externally to the umbilicus of the autosite. [4,7]. In almost all previous case reports of heteropagus, the parasitic twin mass resembled an incomplete fetus, had identifiable anatomical features such as limbs or head and was covered with skin [4,8]. ...
Article
Full-text available
Background: We present the diagnostic dilemma of a neonate with two umbilical soft tissue masses. Case report: The baby had an umbilical mass herniating through the umbilical cord, and another mass hanging from the umbilical mass by a string of tissue. Both masses were amorphous solid soft tissues and the hanging mass had hair on the surface. Clinical diagnosis was umbilical cord teratoma. However, histopathological examination of the masses showed that tissues representing various organs were arranged in cephalocaudal order as in a fetus, revealing that it was a parasitic twin. The hanging mass was probably the cephalic part and the umbilical mass was malformed torso and limbs. Conclusion: This parasitic omphalopagus heteropagus parasitic twin presented as two amorphous masses without externally identifiable anatomic structure, The parasitic twin of omphalopagus heteropagus may have unusual presentations. Histopathological examination was essential to diagnose whether it is a twin or a tumor.
... In the literature, DNA analysis of one case showed that the ACT was dizygotic, confirming the possibility of fusion theory [95]. Another ischemic theory has also been proposed, in which the parasite results from ischemia and resorption of the autosite [92,96]. ...
Article
Full-text available
PurposeAsymmetric conjoined twining (ACT) is a form of conjoined twining which is a rare malformation of monochorionic monoamniotic twin pregnancy. Most publications were single case reports. We reported a cohort of five cases with ACT from a single tertiary medical center and reviewed the case reports of ACT over the last decade to enrich the clinical research of this disease and summarized the clinical features of the disease.Methods We reviewed five cases of ACT admitted in Tianjin Children's Hospital from 17 March, 2008, through 7 March 2017. The cohort was analysed from general information, imaging manifestations, separation surgery, histopathological findings, outcome and follow-up. We searched the English literatures on case reports of ACT over the past decade from the PubMed database and presented details about the clinical characteristics, treatment, and prognosis of all cases.ResultsThere were four males and one female in our cohort. Among the five cases, two parasites were located in epigastrium, two in rachis, and one in retroperitoneum (fetus in fetu, FIF). All of the parasites were separated successfully by operation in five cases and were confirmed to be ACT by histopathology reports. Four patients made an uneventful recovery except for one case of wound infection. All of them were doing well in follow-up. In the literature review, we found 41 cases of exoparasitic heteropagus twining (EHT) and 63 cases of FIF.ConclusionsACT is very rare and usually diagnosed by prenatal ultrasonography (US). Computed tomography (CT) and magnetic resonance imaging (MRI) examinations are essential imaging examinations before separation surgery to delineate the anatomical relationship between the autosite and the parasite. In general, the separation surgery of ACT is less complicated and the prognosis is better compared with the symmetric conjoined twining (SCT).
Article
Heteropagus, or "parasitic," twins are asymmetric conjoined twins in which the tissues of a severely defective twin (parasite) are dependent on the cardiovascular system of the other, largely intact twin (autosite) for survival. The estimated incidence of heteropagus twins is approximately 1 per 1 million live births. Isolated case reports comprise most of published work on this rare congenital anomaly. In the past, review articles have focused narrowly on one particular anatomical subtype of parasitic twin and/or on the anatomicopathology observed. Here, we present the epidemiology, proposed pathoembryogenic origins, anatomical abnormalities, management, and outcomes of the wide array of heteropagus twins described in the English language literature.
Article
Conjoined twins are rare and are classified as symmetrical or asymmetrical, in which a member, the host (autosite), is near normal and bears the parasite, which is incomplete, smaller, and fully dependent for growth on it. This form of conjoined twins is referred to as heteropagus and when attached to the epigastrium of the autosite is called epigastric heteropagus. Only 44 cases of epigastric heteropagus twins have been previously reported in the world literature. We hereby report the successful separation of a pair of heteropagus twins.
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We report a case of a neonate presenting with the rare vascular tumor, Kaposiform hemangioendothelioma. She had a lesion arising from the left ovary with multiple intraperitoneal metastases causing small bowel obstruction. We managed this case with primary surgical resection followed by laparoscopic surveillance of the peritoneal cavity and metastectomy. The child is fit and well and free of tumor after 32 months. Neither this presentation of this tumor nor this management approach has been previously described in the literature.
Article
Heteropagus twins are an extremely rare event with an incidence of 1–2 million live births that represents, sometimes, a real challenge for paediatric surgeons. The majority of cases have complete or partial duplication of the pelvis and/or lower extremities. Thoracic heteropagus conjoined twins is a rare condition in which a grossly defective foetus (the parasite) is attached to the thorax of the main foetus (the autosite). We describe a case of a parasitic heteropagus attached at the chest wall with a rare presentation of giant exomphalos on the autosite. In this situation, the separation procedure was simple after a well-done anatomic study using X-ray, ultrasonography, magnetic resonance and echocardiogram are performed.
Article
Introduction and methodology: Conjoined twins are a rare anomaly that has generated a great deal of interest because of its complex management. We present the experience achieved during 40 years at the Section of Pediatric Surgery, University of Antioquia, in Medellin, Colombia. Results: In the period between 1970 and 2010, nine cases of conjoined twins were treated by our group, six of them at Hospital Universitario San Vicente de Paúl and three at the Social Security Institute. Their distribution was as follows: three pairs of asymmetric twins (parasites); two pairs of thoracoonphalopagus, two pairs of omphaloxigopagus, one pair of pygopagus and one pair of ischiopagus. Discussion and conclusions: Separation of conjoined twins is a rare situation in the practice of pediatric surgery. Therefore, it is important to share and publish the experience achieved in order to improve the short and long-term outcomes. Our experience has taught us the importance of proper prenatal diagnosis, safe preoperative approach, judicious planning of surgery and rigorous postoperative follow-up.
Article
Full-text available
Epigastric heteropagus (EH) refers to asymmetrically conjoined twins in whom an incomplete parasite is attached to the autosite's epigastric region from the xiphisternum to the umbilicus. We herein report an extremely rare case of EH in which unexpected rapid recurrence occurred 22 months after excision of the parasite. The recurrent mass comprised the intestinal wall with peristalsis-like movement, urogenital tissues, and hepatic tissue of the parasite. The recurrence was caused by a remnant of the parasite that extended from the autosite's xiphisternum to intra-abdominal cavity.
Article
Objective. The purpose of this study was to describe the imaging and pathologic findings of 2 cases of complex neonatal abdominal masses and to discuss the probable common embryologic etiology of fetus in fetu (FIF) and fetaform teratomas. Methods. Two male neonates had complex cystic abdominal masses, 1 of which was diagnosed prenatally, and both had abdominal sonography. One patient also had abdominal computed tomography. Both patients subsequently underwent surgical resection, with pathologic and genetic analysis of these masses. Results. One patient had typical imaging, pathologic, and genetic findings of FIF. The second patient had a well-formed mass that was diagnosed pathologically as a teratoma yet had most of the criteria for FIF that have been set forth in recent embryologic literature. Conclusions. Recent concepts regarding the origin of FIF suggest that it is part of a spectrum of monozygotic twinning gone awry, ranging from conjoined twins at one end to fetaform teratomas at the other. The imaging and pathologic features of these 2 cases serve to reinforce this concept.
Article
We report on a case of conjoined twinning (CT) consistent with fusion of two embryos followed by resorption of the cranial half of one of them, resulting in a normal male baby with the lower half of a male parasitic twin fused to his chest. Fluorescent in situ hybridization (FISH) studies suggested that the parasitic twin was male, and DNA typing studies demonstrated dizygosity. Although incomplete fission is the usual explanation for conjoined twins, the unusual perpendicular orientation of the parasite to the autosite supports a mechanism observed in mares in which early fusion of two embryos is followed by resorption due to compromised embryonic polarity. Am. J. Med. Genet. 73:239–243, 1997. © 1997 Wiley-Liss, Inc.
Article
A review of over 1,800 publications concerning the embryology and pathologic anatomy of conjoined twins provides convincing evidence that they all result from the secondary union of two originally separate monovular embryonic discs. This “fusion” theory seems to be confirmed by the adjustments to union and the pattern and incidence of specific anomalies at the proposed sites of conjunction in more than 1,200 cases, all of which can be arranged in two uninterrupted series of cases, the one united dorsally (in the neural tube) and the other, ventrally (over a shared a yolk sac). No theoretical “fission” of the vertebrate embryo at any stage of development, in any plane, in any direction can explain (1) the selection of the observed sites of fusion, (2) the details of the union, or (3) the limitation to the specific areas in which the twins are found to be joined. Part I of this disquisition deals with the pertinent normal and theoretical embryology, the adjustments to union, and the parasitic cases, as well as conjoined triplets and quadruplets, and a comparison of oviparous and viviparous embryos. Part II (in a subsequent issue of this journal) will compare and correlate the abnormalities of the various organ systems involved in 1,200 cases. Clin. Anat. 13:36–53, 2000. © 2000 Wiley-Liss, Inc.
Article
Parasitic twins can attach to the host at a number of different locations. The most usual variant is caudal duplication (dipygus), where the parasite consists of additional pelvic and lower limb structures attached to the pelvis of the dominant twin. Less commonly, the rudimentary twin can attach to the anterior thorax, the thoracic spine, or the epigastrium, as in this case. A 13-year-old boy was successfully managed and represents the eighth case of epigastric heteropagus reported, and the oldest presentation of such a case.
Article
A 3-day-old boy baby presented with a cystic umbilical swelling covered mostly by skin and partly by amnion. On the surface, an early embryo-like structure was attached (facial features and limb buds). The deeper aspect of it was composed of large cystic and tubular structures and solid organs resembling liver and spleen. It was labeled as acardiac amorphous parasitic twin, the first of its kind to be reported.
Article
The descriptive epidemiology of conjoined twinning in the United States was investigated using data from the Birth Defects Monitoring Program (BDMP), a nationwide congenital malformations surveillance system that monitors discharge diagnoses associated with a third of the births in the United States. This is the largest recorded series concerning conjoined twins; data were analyzed on 7,903,000 births monitored by the BDMP in the period 1970-1977. The analysis identified 81 sets of conjoined twins, for a crude incidence of 10.25 per million births. The most common types of conjoined twins were thoracoomphalopagus (28%), thoracopagus (18%), omphalopagus (10%), parasitic twins (10%), and craniopagus (6%). Conjoined twins are more common among females than males, and in nonwhites than whites. No maternal age effect was found. There was no evidence of seasonal or temporal clustering of the cases. The large number of conjoined twins who had birth defects that are not obviously linked to the conjoining (particularly neural tube defects and orofacial clefts) may provide insights into the pathogenesis of birth defects resulting from disordered embryonic migration and fusion.
Article
Epigastric heteropagus refers to unequal and asymmetric conjoined twins in which the dependent component (parasite) is smaller and usually attached to the epigastrium of the dominant component (autosite). Epigastric heteropagus is a very rare type of conjoined twins. It is generally assumed that conjoined twins represent a form of monozygotic twinning, but there has been no confirmation of this monozygotic hypothesis. Epigastric heteropagus twins differ in several ways from symmetrical conjoined twins. These include male preponderance, and no major connection of vessels, bowels, or bones. These significant characteristics suggest to the authors that the fusion of two fertilized ova and the atrophy of one fetus resulted in this interesting malformation. However, a DNA study indicated monozygotic origin in their case. The possible pathogenesis was ischemic atrophy of the body structure of the monozygotic conjoined twins at an early gestational age.
Article
We report on a case of conjoined twinning (CT) consistent with fusion of two embryos followed by resorption of the cranial half of one of them, resulting in a normal male baby with the lower half of a male parasitic twin fused to his chest. Fluorescent in situ hybridization (FISH) studies suggested that the parasitic twin was male, and DNA typing studies demonstrated dizygosity. Although incomplete fission is the usual explanation for conjoined twins, the unusual perpendicular orientation of the parasite to the autosite supports a mechanism observed in mares in which early fusion of two embryos is followed by resorption due to compromised embryonic polarity.
Article
Asymmetrical conjoined twinning is an extremely rare congenital anomaly constituting only 1%-2% of all conjoined twins. In epigastric heteropagus twins (EHT), the dependent portion (parasite) is smaller than the host (autosite). The embryopathy is related to incomplete cleavage of the embryo at 2 weeks of gestation. However, some form of ischaemic insult in early gestation leads to selective atrophy of the cranial part of one of the monozygous twins. We report our experience with four cases of EHT and a review of the literature with a discussion of possible embryopathy.
Article
During the course of researching the embryologic etiology of conjoined twins, more than 1260 individual cases were collected from the literature and the reported abnormal anatomy tabulated and evaluated in the light of known embryology. It soon became apparent that the association of conjoined twins and their parasites with fetuses in fetu, acardiacs, and teratomas was more frequent than could be attributed to chance. These anomalous fetuses form a continuum, strongly suggesting that they are all variations of abnormal conjoined twinning, with the site of union and the extent of damage (or defect) of one embryo resulting in (1) an externally attached parasitic twin, (2) an enclosed fetus in fetu, (3) an internal teratoma, or (4) an acardiac connected via the placenta. Common patterns among them are a family history of twinning, the predominance of females, and the frequent presence of a twin or triplet accompanying the malformation. The several reports of chromosomal abnormality suggest that perhaps, at least on occasion, it is a genetically imperfect embryo that develops into a defective fetus. Of singular importance is the fact that rarely, if ever, is either a functional heart or a competent brain found in any of these abnormal fetuses, suggesting that the etiology of all of them is a primary cardiac malformation with secondary disruption in the development of the brain.
Article
Conjoined twins occur in approximately one of every 50,000 to 200,000 births. Atypical or parasitic conjoined twins result from the embryonic death of one twin, which leaves behind body parts vascularized by the primary twin. Omphalopagus refers to conjoined twins joined at the level of the umbilicus. The authors report a case of atypical omphalopagus involving an acardiac, acephalic, parasitic twin and a host twin with a large omphalocele, transposition of the great arteries, and aortic coarctation. The authors briefly review reported cases of parasitic omphalopagus and emphasize the role of intensive neonatal care, preoperative planning, and staged surgical intervention in the successful management of complicated variants.
Article
Epigastric heteropagus twins (EHT) is a rare form of conjoined twins. It refers to unequal and asymmetric conjoined twins in which the dependent part (parasite) is attached to the epigastrium of the dominant part (autosite). The authors herein report four cases of EHT. Omphalocele was present in 3 patients. Surgical excision of the parasite and repair of the abdominal wall defect were successful in three cases. Three infants had associated cardiac anomalies and one of them died during surgery from cardiopulmonary failure.
Article
Introduction: Attention is drawn to the spontaneous incidence of twinning, both dizygotic and monozygotic in different mammalian species. Conjoined twinning, however, only arises when the twinning event occurs at about the primitive streak stage of development, at about 13-14 days after fertilisation in the human, and is exclusively associated with the monoamniotic monochorionic type of placentation. It is believed that the highest incidence of conjoined twinning is encountered in the human. While monozygotic twinning may be induced experimentally following exposure to a variety of agents, the mechanism of induction of spontaneous twinning in the human remains unknown. All agents that are capable of acting as a twinning stimulus are teratogenic, and probably act by interfering with the spindle apparatus. Discussion: The incidence of the various types of conjoined twinning is discussed. Information from the largest study to date indicates that the spontaneous incidence is about 10.25 per million births. The most common varieties encountered were thoraco-omphalopagus (28%), thoracopagus (18.5%), omphalopagus (10%), parasitic twins (10%) and craniopagus (6%). Of these, about 40% were stillborn, and 60% liveborn, although only about 25% of those that survived to birth lived long enough to be candidates for surgery. Conjoined twinning occurs by the incomplete splitting of the embryonic axis and, with the exception of parasitic conjoined twins, all are symmetrical and "the same parts are always united to the same parts". Fusion of monozygotic twins is no longer believed to be the basis of conjoined twinning. Accounts are provided of the anatomical features of each of the commonly encountered varieties.
Article
To describe a first case of parasitic twin achieved after intracytoplasmic sperm injection (ICSI). Case report. Perinatal center at a Japanese university hospital. A 30-year-old pregnant Japanese woman with a history of secondary infertility achieved after ICSI was diagnosed with an omphalopagus parasitic twin pregnancy by prenatal ultrasound at 28 weeks of gestation. A female infant was delivered by scheduled cesarean section at 30 weeks of gestation. The cesarean section was performed for dystocia. Brief review of parasitic twin and malformations in fetuses achieved after ICSI. Resuscitation was not done because of the poor prognosis for both fetuses. Molecular analysis with informative genetic markers is consistent with monozygotic pregnancy. A careful ultrasound examination is indicated to detect additional anomalous findings in twin fetuses achieved after ICSI.
Article
A rare case of a newborn girl presenting with a mass representing an aborted parasitic twin attached to the back in the midline over the lumbosacral region (parasitic rachipagus) is reported. Rudimentary digits were attached to the mass, and in one area, the overlying skin resembled scrotal skin. A depression resembling an anal dimple was also present on the surface of the mass. Investigations showed a well-developed long bone and other small bones within the parasite, and sacral spina bifida in the autosite. Successful surgical excision of the parasitic mass was performed. A review of the literature pertaining to parasitic rachipagus twinning is presented.
Article
The purpose of this study was to describe the imaging and pathologic findings of 2 cases of complex neonatal abdominal masses and to discuss the probable common embryologic etiology of fetus in fetu (FIF) and fetaform teratomas. Two male neonates had complex cystic abdominal masses, 1 of which was diagnosed prenatally, and both had abdominal sonography. One patient also had abdominal computed tomography. Both patients subsequently underwent surgical resection, with pathologic and genetic analysis of these masses. One patient had typical imaging, pathologic, and genetic findings of FIF. The second patient had a well-formed mass that was diagnosed pathologically as a teratoma yet had most of the criteria for FIF that have been set forth in recent embryologic literature. Recent concepts regarding the origin of FIF suggest that it is part of a spectrum of monozygotic twinning gone awry, ranging from conjoined twins at one end to fetaform teratomas at the other. The imaging and pathologic features of these 2 cases serve to reinforce this concept.
Article
A sacral parasite is a rare congenital anomaly classified etiologically as duplicitas asymmetros, where the parasitic mass is regarded as the tissue remnants of an unequally conjoined twin. We, herein, report a case of a sacral parasitic mass found in a female neonate. A huge sacral mass was found at 30 weeks of gestation by fetal ultrasonography. The fetus was delivered by a Caesarean operation at 37 weeks and 6 days of gestation. The alpha-fetoprotein (AFP) level was 174,640 ng/ml. The mass separated by an operation on the day after her birth, contained structures similar to imperfect limbs and backbone. A variety of tissue and organs having derived from three germ layers were identified within the mass and showed a tendency to be highly differentiated. Even though a large proportion of the central nervous system tissue showed immature and dysplastic features, there were no evidences suggesting the presence of neoplasm. The infant has shown normal growth and is doing well without a recurrence of the sacral mass or any elevation in the serum AFP level during the12-month follow-up. We therefore believe that the present case should be considered a sacral parasite, rather than a sacrococcygeal teratoma. Although it should be recognized that such sacral parasite is very rare, this case provides further information that can be useful for diagnosis.
1 A 15 × 9 cm amorphous abdominal mass Superiorly there is a focal collection of dark hairs and several small abortive appendages, and inferiorly a region reminiscent of a vulva
  • Fig
Fig. 1 A 15 × 9 cm amorphous abdominal mass. Superiorly there is a focal collection of dark hairs and several small abortive appendages, and inferiorly a region reminiscent of a vulva. E38 E. Satter, S. Tomita
Heterophagous Conjoined twins due to fusion of two embryos: Report and Review.
  • Longrono R.
  • Garcia-Lithgow C.
  • Harris C.
Longrono R, Garcia-Lithgow C, Harris C, et al. Heterophagous Conjoined twins due to fusion of two embryos: Report and Review. Am J Med Genet 1997;73:239-43.