J Pediatr Rev. 2013;1(1)64-69

*Corresponding Author:ZhilaTorabizadeh MD, Associate Professor of PathologyMailing Address: Department of pathology, Emam Hospital, Amir Mazandarani boulevard, Sari, IranTel: +98 151 2261701-4Email: zhtorabi@yahoo.com

Mermaid syndrome, Sirenomelia: A case report and review of literature

Anahita Nosrati1

Farshad Naghshvar2

Zhila Torabizadeh3*

Omid Emadian4

1,2,3,4Department of Pathology, Faculty of Medicine, Mazandaran University of Medical Science, Sari, Iran.

ARTICLE INFO ABSTRACT

Article type:Case and Review

Sirenomelia is a rare anomaly of caudal region of the body presentedwith fusion of lower limbs in which Genito-urinary, Gastrointestinal,Cardiovascular and Neural tube anomalies are found in most cases. Weintroduce a case of severe oligohydramnios, which had characteristicaspects of Sirenomelia at the time of delivery and review the pertinentarticles. All in all it is our aim to present another case of sirenomelia toadd to existing knowledge and data about the condition in order to makean earlier diagnosis and put an end to pregnancy safely in advance.

Article history:Received: 15 Sep 2012Revised: 29 Dec 2012Accepted:8 Jan 2013

Keywords:Sirenomelia, Mermaidsyndrome, Oligohydramnios,Dextrocardia

http://jpr.mazums.ac.ir

IntroductionSirenomelia or Mermaid syndrome wasoriginally stated by Rocheas in 1542 and Palfyain 1553 and named after the mythical GreekSiren. 1,2, 3For the first time, Homer explained inthe tempting singing creatures that seducedsailors to their deaths.4 Historical texts ofaround 2500 BC found in several Europeancountries included references to femalehybrids.4It occurs about 1 in 100,000 livebirths.5The most striking yet inconstant view ofthis malformative disorder is the complete orpartial fusion of the lower limbs.It is acongenital anomaly including renal agenesis,ambiguous external genitalia, imperforate anusand blind intestinal loop.6,7 Occasionally

double inferiorVena cava and angiomatouslumbosacral myelocystocele are reported aswell.8,9Most of the Sirenomelia come to an endas stillbirth.6Only a few numbers of whom havecited to be alive after delivery.10,11Interestinglyit has been said that there is an association withmaternal diabetes.1,12Hence we aim to present afetus with features of mermaid syndrome in ourdepartment for first time and review properarticles.

Case presentationA 34 years old primigravid pregnant woman at25 weeks of gestation is counseled to terminateher pregnancy because of marked

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oligohydraminos that was incompatible withlife. She had undergone an Ultrasoundexamination at 10 weeks gestation withoutapparently any reported abnormality in fetus.There were no medical or obstetric risk factors.There was no personal or family history forDiabetes Mellitus or congenital anomalies inrelatives.Routine Ultrasound examination, at 24 weeks ofgestation revealed a live single fetuscorresponding to 21 weeks gestation, weight:270 gram. There were no single measurablepocket of amniotic fluid (severeOligohydramnios); moreover, fetal kidneys,urinary bladder and stomach were notvisualized.A repeat Ultrasound was done in anotherinstitute and it turned out to be quitedextrocardia and left diaphragmatic hernia.Since there was severe oligohydramnios, thesonographer was not able to precisely assessboth lower limbs and lumber spines. Eventuallyafter couple’s consent termination is done at 25weeks.During autopsy procedure, fusion of the wholelower limbs from the hips to the ankles wasfounded out (Figure-1). In addition, it wasrealized syndactyly of the left foot with softtissue union of the first and second toes.The head was compressed and showed low setears.The face displayed bilateral complete lip andpalate clefts. The lumber spine showed a defectat the level of - . There was no analopening and no discernable genitalia.The umbilical stump revealed just one arteryand one vein. Complete absence ofgenitourinary system was evident. Kidneys,ureters and bladder were absent too. There wasno stomach, and the midgut loop was blindlyended. The heart was located in the right side ofthe chest cavity (dextrocardia) (Figure-2). Thelungs were non-flatted .The mentioned findings

were consistent with the diagnosis ofsirenomelia.

Figure 1. Mermaid fetus, showing fused lowerlimbs and lip and palate clefts

Microscopic examination revealed just partiallyautolysed organs and generally not specialpathologic changes.

Figure 2. Mermaid fetus, Dextrocardia

DiscussionSirenomelia is a rare and lethal congenitalanomaly with unknown etiology showingabnormal development of the caudal region ofthe body involving varying degrees of fusion ofthe lower limbs with or without bonydefects(Table-1).Other visceral defects such as hypo plasticlungs, cardiac agenesis, absent genitalia,digestive defects, absent kidney and bladder,

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Table1.Antenatal cases of mermaid syndrome diagnosed in the first trimesterAuthor Year of publication Number of referencesDuhamel B 1961 26Von Lennep E 1985 19Steven RE, Hibelink DR 1986 17,18Stocker JT 1987 27Sirtori M 1989 21Tang TT, Rodriguez JI 1991 13,14Sarpong S, Kallen B 1992 20,5Lynch SA 1995 24Jaiyesimi F 1998 23Aslan H 2001 12Taori KB , Stanton MP 2002 7,11Browne M 2004 9Pinette MG 2005 15Bakhtar O, Romano S,Vankeirsblick j, Ladure H 2006 22,4,2,3Akbayir O 2008 29Sikandar R 2009 1Fadhlaoui A 2010 25

Ugwa RO 2011 6Our current case 2012 -

vertebral and central nervous system defect arealso reported.13, 14The poor prognosis is usuallyforecasted depending on some kind of thevisceral anomalies. Death usually stems fromrenal agenesis or dysgenesis15, which therelikely seems to be happened to our case.

Risk factorsMany different kinds of theories have beensuggested such as maternal diabetes6, 7, 8, 16;however ,our mother was not known to bediabetic.Genetic and environmental factors arealso noted .7, 17 Hibelink et al pointed out thatteratogenic agents like cadmium element andlead may cause sirenomelia in the goldenhamster.18 The likely potential teratogeniceffect of vitamin A is mentioned by Vonlennepet al19 and cocaine 20 or irradiation exposure21

as well . Association of the sirenomelia withnew reproductive technologies, namelywith ICSI (Intra Cytoplasmic Sperm Injection)was also described.22

Besides, it has been reported in twins. Reportsindicate a 100–150 times higher incidence inmonozygotic twins relative to dizygotic twinsor singletons.23In our patient, no twin gestationor family history of twinning was found out.Another huge concern is genetic transmission.Lynch et al 24realized an autosomal type ofcaudal dysgenesis , but no chromosomal defectsare discovered in mermaid syndrome .This wasan encouraging view for our mother to have sortof genetic consultation. Genetic counselingshould even be suggested because thementioned risk of recurrence is fairly 3–5%.25All abnormalities in our case likeimperforate anus, a neural tube defect, limbsabnormality, cardiac dextrocardia and renalagenesis are frankly compatible with conceptof sirenomelia in other similar related articles aswell.25

PathogenesisThe pathogenesis of this syndrome has beendiscussed over time. Numerous theories have

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been proposed to explain its origin. Fivepathogenetic theories of sirenomelia aredescribed:1. An embryological insult 15

2. Vascular steal theory17

3. As part of the caudal regression syndrome(CRS) 26

4. As part of the VACTERL syndrome(vertebral defects, anal atresia, cardiacdefects, tracheo-esophageal fistula, renalanomalies, and limb abnormalities)23

5. External forces acting on the caudalextremity.25

From an embryological point of view, thesirenomelia sequence comes from an ‘caudalmesoderm damage taking place between days28–32 of fetal life(first theory ).15 Thereforethere are renal agenesis, lack of genital organs,imperforated anus, vertebral dysgenesis, andlower limb atrophy.25

Second theory, Sirenomelia is probably aconsequence of an abnormal blood supply ofcaudal parts of the embryo. A divergedabnormal vessel carries blood throughthe umbilical cord into the placenta. The vessel"steals" blood from the structures located belowits origin from the tissues of fetal caudal part.16

A third theory regards sirenomelia as part of thecaudal regression syndrome (CRS) , a rarecongenital anomaly described by Duhamel26including sacrum dysgenesis, spinal corddefect , urinary incontinence and misplacedlower limbs. Some inconstant features are renaldysgenesis and imperforate anus.According to the fourth theory syndrome in theliterature, sirenomelia could be a member of theVACTERL syndrome. VACTERL syndromeconsists of vertebral, anal, cardiovascular,trachea- esophageal fistula, renal and limbdysgenesis. A major overlap has been realizedin the phenotypic features of sirenomelia andVACTERL.23

A fifth theory is the pressure theory statinghypoplasia of caudal extremity is owing to

external forces.25 However not accepted on thewhole.25 Other less appropriate theories havealso been proposed. Yet the overlap in thesesyndromes/theories is a matter of debate in thescientific world as to the uniqueness or varietiesof these syndromes.

ClassificationStocker and Heifetz27 classified the sirenomeliasequence into 7 types as below:1. All thigh and leg bones are present2. Single fibula3. Absent fibula4. partially fused femurs fused fibulae5. partially fused femurs6. single femur single tibia7. single femur absent tibiaWe did not have any radiographs of the lowerlimbs, but our case turned out to be pretty typesix.

DiagnosisIt has been reported the possible first trimesterdiagnosis of mermaid fetus.3 Although thepregnant mother was supervised, it didn’t takeplace in our case .The use of colordopplerimaging and MRI is claimed to have beneficialinfluence on in advance assessment.1, 2, 28

PrognosisSirenomelia is fatal in most cases because of thecharacteristic pulmonary hypoplasia and renalagenesia. In children borned alive death willoccur rather within a couple of days followingbirth 27. Presence of kidney is mandatory tosurvive. Murphy et al 24 reported a survivedsirenomelia neonate. Laparotomy andcolostomy were done, and eventually lowerextremities were separated. It stands to reasonthat its managing is tough and rather costly withunforeseeable results in the case described byStanton.11The patient had five interventions

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between the age of 15 days and 4 years (she hasbeen bedridden and dependent).

ConclusionSirenomelia is a kind of scarce and deadlycongenital malformation .As far as we areconcerned it is pretty much uncommoncondition, so giving elaborated information mayprovide clinicians with a great chance toterminate the pregnancy in advance much moresafely.

AcknowledgementsWe thank Dr K. khodadadi and Miss M.Rashidi who provided us with advancedmedical search and technical support to reachour aim.

Conflict of InterestNone declared.

Funding/SupportNone declared.

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