Caudal regression syndrome versus sirenomelia: a case report

Prenatal sirenomelia diagnosis in the first trimester: A case report and literature review

Key Clinical Message

Sirenomelia is a lethal condition in the perinatal period. The sonographic examination in the first trimester can effectively detect sirenomelia with a high degree of accuracy. Furthermore, vascular examinations using color flow imaging and augmented imaging techniques such as 3D sonography can improve diagnostic accuracy. Parents should get advice from a multidisciplinary team concerning sirenomelia care and prognosis as soon as possible.

Abstract

Sirenomelia is a rare condition with an uncommon congenital malformation; its most remarkable feature is lower extremity fusion with multiple visceral anomalies. Accordingly, the appearance resembles a mermaid's tail, hence mermaid syndrome. Sirenomelia has an incidence rate of 1.5-4.2 per 100,000 births, a male-to-female 2.7:1 ratio, and shows no differences across races. The condition is generally associated with renal agenesis, exterior genitalia defects, a single umbilical artery, and an imperforate anus. Here, we describe the first sirenomelia case in our hospital; a 13-week-old fetus with conjoined lower limbs was identified by ultrasound in the first trimester. We discuss this rare case with reference to the literature and provide insights on diagnosing this condition by ultrasound.

Sirenomelia in Twin Pregnancy: A Case Report

Sirenomelia is a rare congenital disorder that was once thought to be a severe case of caudal regression but is now thought to be entirely separate. It is often referred to as the "mermaid syndrome" because it causes the lower limbs to atrophy to varying degrees, giving the impression of a mermaid's tail or fin. The syndrome is often viewed as fatal due to the accompanying visceral deformities. Our case was a live born, delivered at term by caesarean section, to a 30-year-old third gravida having twin pregnancy. Examination of the baby revealed caudal dysgenesis with fusion of lower limbs, non-identifiable external genitalia and anus. The infant survived for 11 hours after birth. We report this case due to their rarity and term live birth. While sirenomelia is uncommon, the absence of distinct lower limbs on ultrasonography in the presence of oligo or anhydramnios may prompt consideration of the diagnosis of sirenomelia.

Sirenomelia: A case report

Sirenomelia also known as mermaid syndrome is a partial or complete fusion of lower extremities associated with visceral anomalies. It is a rare anomaly with a poor prognosis. Maternal age less than 20 years, maternal diabetes mellitus, and monozygotic twinning are some of the known risk factors. Diagnosis can be made via antenatal ultrasound or typical physical appearance after birth. A 2200 g baby was born from 18-year-old non-consanguineous mother via assisted breech delivery. The baby had fused lower limbs with 10 toes, absent external genitalia, and a single umbilical artery. It was small for gestational age. The baby was passed away after 30 min of birth. Young maternal age (18 years) was the identified risk factor for sirenomelia in this case. We recommend an early routine ultrasound anomaly scan in all pregnant women particularly for early detection and termination of pregnancy as the prognosis is poor. Avoiding teenager pregnancy and strict control of blood sugar in diabetic mothers can decrease this anomaly.

Sirenomelia, case report and review of the literature

We present a case of sirenomelia diagnosed in the first trimester of pregnancy. The ultrasound examination showed fused lower extremities and an anechoic structure in the lower abdomen that is clue in the early diagnosis. The postmortem study showed the existence of a single umbilical artery (vitelline artery), with an origin in the abdominal aorta. This finding not only explained the presence of a vascular steal with subsequent underdeveloped of pelvic organs, but also differentiated this condition from caudal regression syndrome.

Caudal Regression Syndrome-A Review Focusing on Genetic Associations

Caudal regression syndrome (CRS) represents a spectrum of clinical phenotypes with varying degrees of malformation of the lower body with involvement of structures deriving from all 3 layers of the trilaminar embryo. We review areas of active investigation in the diagnosis, etiology, epidemiology, and treatment of the disease with a focus on underlying genetics. CRS pathobiology is complex and multifactorial with a significant contribution from environmental factors as evidenced in twin studies. Contemporary genomic and genetic investigations in both human primary tissue and murine in vitro and in vivo models implicate various genes associated with caudal differentiation and neural cell migration in embryogenesis. A large number of identified targets center around the metabolic regulation of retinoic acid and its derivatives. Dysregulation of retinoic acid homeostasis has been associated with abnormal embryonic cell migration, differentiation, and organogenesis with resulting malformations and agenesis in both a laboratory and a clinical setting. There appears to be a significant overlap in potential genetic targets with CRS and other developmental syndromes with similar presentations, such as VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities) association. CRS represents a spectrum of caudal developmental abnormalities with treatment options limited to mild and moderate expressions of disease. Continued research is necessary to further clarify mechanisms of disease pathobiology and complex polygenetic and environmental interaction. Despite this, progress has been made in identifying genetic targets and downstream effectors contributing to preclinical and clinical progression.

Mermaid Syndrome: A Case Report of a Rare Congenital Anomaly in Full-Term Neonate with Thumb Deformity

The mermaid syndrome (sirenomelia) is an extremely rare anomaly, an incidence of 1 in 100,000 births, in which a newborn born with legs joined together featuring a mermaid-like appearance (head and trunk like humans and tail like fish), and in most cases die shortly after birth. Gastrointestinal and urogenital anomalies and single umbilical artery are clinical outcome of this syndrome. There are two important hypotheses for pathogenesis of mermaid syndrome: vitelline artery steal hypothesis and defective blastogenesis hypothesis. The cause of the mermaid syndrome is unknown, but there are some possible factors such as age younger than 20 years and older than 40 years in mother and exposure of fetus to teratogenics. Here, we introduced 19-year-old mother's first neonate with mermaid syndrome. The mother had gestational diabetes mellitus and neonate was born with single lower limb, ambiguous genitalia, and thumb anomalies, and 4 days after birth, the neonate died due to multiple anomalies and imperforated anus.

Exposure to methylergonovine maleate as a cause of sirenomelia

BACKGROUND

Sirenomelia is a rare, but deadly condition characterized by fusion of the lower limbs, lower spinal column defects, severe malformations of the urogenital and lower gastrointestinal tract, and an aberrant abdominal umbilical artery.

METHODS

The two main hypotheses, not mutually exclusive, that have been advanced to explain the pathogenesis of sirenomelia are the blastogenetic theory and the vascular disruption theory.

RESULTS

We describe a case of sirenomelia, probably associated with the use of methylergonovine maleate, an ergot alkaloid, during the first weeks of pregnancy.

CONCLUSION

On the basis of the mechanisms of vascular disruption and early administration of methylergonovine maleate at a critical stage of organogenesis, we conclude that exposure to methylergonovine maleate could be the cause of the development of sirenomelia. Birth Defects Research (Part A) 106:643-647, 2016. © 2016 Wiley Periodicals, Inc.

Sirenomelia with associated systemic anomalies: an autopsy pathologic illustration of a series of four cases

Sirenomelia, a developmental defect involving the caudal region of the body, is associated with several internal visceral anomalies. We report a detailed spectrum of anomalies in an autopsy study of four fetuses with sirenomelia (gestational ages - 20, 21, 22.4, and 22.5 weeks). Three of the fetuses had single umbilical artery, with genitourinary and gastrointestinal anomalies. Central nervous system anomalies were evident in two of the fetuses, with alobar holoprosencephaly in one and lumbar meningomyelocele in another. The most common gastrointestinal anomaly was blind ended gut (imperforate anus), while esophageal atresia and omphalocele were noted in one case each. Renal hypoplasia was seen in two fetuses, renal agenesis in one and cystic renal dysplasia was noted in one case. Literature regarding pathogenesis of this condition is briefly discussed.

Sirenomelia with oesophageal atresia: a rare association

We are reporting a rare case of sirenomelia with oesophageal atresia. Sirenomelia is a lethal sporadic defect of which lower gastrointestinal tract anomalies are characteristic findings. Respiratory and upper gastrointestinal tract malformations like oesophageal atresia occur in about 20-35% of cases. Though its occurrence has been described, it has been reported only rarely. This report aims at describing this uncommon association along with its histological features.

Sirenomelia apus: a rare deformity

Sirenomelia also known as the mermaid syndrome, is a rare congenital malformation of uncertain etiology. It is characterized by fusion of the lower limbs and commonly associated with severe urogenital and gastrointestinal malformations. There are approximately 300 cases reported in the literature, 15% of which are associated with twinning, most often monozygotic. The syndrome of caudal regression is thought to be the result of injury to the caudal mesoderm early in gestation.

Spectrum of congenital anomalies in pregnancies with pregestational diabetes

BACKGROUND

Maternal pregestational diabetes is a well-known risk factor for congenital anomalies. This study analyses the spectrum of congenital anomalies associated with maternal diabetes using data from a large European database for the population-based surveillance of congenital anomalies.

METHODS

Data from 18 population-based EUROCAT registries of congenital anomalies in 1990-2005. All malformed cases occurring to mothers with pregestational diabetes (diabetes cases) were compared to all malformed cases in the same registry areas to mothers without diabetes (non-diabetes cases).

RESULTS

There were 669 diabetes cases and 92,976 non diabetes cases. Odds ratios in diabetes pregnancies relative to non-diabetes pregnancies comparing each EUROCAT subgroup to all other non-chromosomal anomalies combined showed significantly increased odds ratios for neural tube defects (anencephaly and encephalocele, but not spina bifida) and several subgroups of congenital heart defects. Other subgroups with significantly increased odds ratios were anotia, omphalocele and bilateral renal agenesis. Frequency of hip dislocation was significantly lower among diabetes (odds ratio 0.15, 95% CI 0.05-0.39) than non-diabetes cases. Multiple congenital anomalies were present in 13.6 % of diabetes cases and 6.1 % of non-diabetes cases. The odds ratio for caudal regression sequence was very high (26.40,95% CI 8.98-77.64), but only 17% of all caudal regression cases resulted from a pregnancy with pregestational diabetes.

CONCLUSIONS

The increased risk of congenital anomalies in pregnancies with pregestational diabetes is related to specific non-chromosomal congenital anomalies and multiple congenital anomalies and not a general increased risk.

Sirenomelia: an epidemiologic study in a large dataset from the International Clearinghouse of Birth Defects Surveillance and Research, and literature review

Sirenomelia is a very rare limb anomaly in which the normally paired lower limbs are replaced by a single midline limb. This study describes the prevalence, associated malformations, and maternal characteristics among cases with sirenomelia. Data originated from 19 birth defect surveillance system members of the International Clearinghouse for Birth Defects Surveillance and Research, and were reported according to a single pre-established protocol. Cases were clinically evaluated locally and reviewed centrally. A total of 249 cases with sirenomelia were identified among 25,290,172 births, for a prevalence of 0.98 per 100,000, with higher prevalence in the Mexican registry. An increase of sirenomelia prevalence with maternal age less than 20 years was statistically significant. The proportion of twinning was 9%, higher than the 1% expected. Sex was ambiguous in 47% of cases, and no different from expectation in the rest. The proportion of cases born alive, premature, and weighting less than 2,500 g were 47%, 71.2%, and 88.2%, respectively. Half of the cases with sirenomelia also presented with genital, large bowel, and urinary defects. About 10-15% of the cases had lower spinal column defects, single or anomalous umbilical artery, upper limb, cardiac, and central nervous system defects. There was a greater than expected association of sirenomelia with other very rare defects such as bladder exstrophy, cyclopia/holoprosencephaly, and acardia-acephalus. The application of the new biological network analysis approach, including molecular results, to these associated very rare diseases is suggested for future studies.

First trimester diagnosis of sirenomelia: a case report and review of the literature

Sirenomelia sequence is a rare lethal pattern of congenital anomalies characterized by a number of hallmark skeletal anomalies, including fusion of the lower extremities or a single lower limb, bilateral renal agenesis or dysgenesis with absent or hypoplastic renal arteries, oligohydramnios, and the presence of aberrant vasculature. The etiology is still controversial. Prognosis is very poor, with the babies being stillborn or succumbing soon after birth. In the second trimester, oligohydramnios due to renal agenesis makes the diagnosis of sirenomelia difficult. Conversely, in the first trimester, the amniotic fluid volume is usually normal, unrelated to the fetal urine production. Therefore, a first-trimester or early second trimester anatomic survey of the fetus is proposed as preferable and more accurate for the diagnosis of this rare anomaly. In this article, we report a case of sirenomelia detected by two- and three-dimensional ultrasound in the 11th week of gestation and the associated literature is discussed.

Multidisciplinary surgical approach to a surviving infant with sirenomelia

Sirenomelia is an extremely complex and rare malformation with different degrees of lower-extremities fusion associated with gastrointestinal, musculoskeletal, vascular, cardiopulmonary, and central nervous system malformations. In the English literature, there are only 5 reports of infants surviving with this condition. In our case, a 2540-g female infant was born with normal vital signs, no facial dysmorphism, and a complete soft tissue fusion of the lower limbs, from perineum to ankles. Radiologic examinations revealed an intestinal atresia and a single pelvic kidney, with a unique ureter, 2 femurs, 2 tibias, 2 fibulas, and 2 feet (simpus dipus). At 7 months of age, a multidisciplinary surgical team achieved complete separation of the lower limbs, with independent vascular and nerve supplies. At the time of this writing, the infant was 28 months old and had a regular growth curve. Many future reconstructive surgeries have been planned to achieve an acceptable quality of life for this infant.