Sirenomelia: Difference between revisions

Revision as of 19:06, 22 March 2025

A rare congenital malformation characterized by fused lower limbs

Sirenomelia, also known as mermaid syndrome, is a rare congenital developmental disorder characterized by anomalies of the lower spine and lower limbs. The condition results in the fusion of the legs, giving the appearance of a mermaid's tail, hence the name. Sirenomelia is associated with a range of other malformations, particularly affecting the genitourinary system, gastrointestinal tract, and skeletal system.

Epidemiology

Sirenomelia is an extremely rare condition, with an estimated incidence of 1 in 100,000 live births. It is more common in males than females, with a male-to-female ratio of approximately 3:1. The condition is often associated with maternal diabetes, which is considered a significant risk factor.

Pathophysiology

The exact cause of sirenomelia is not well understood, but it is believed to result from a disruption in the normal development of the caudal region of the embryo. This disruption may be due to abnormal vascular supply, specifically the "steal phenomenon," where the blood supply is diverted from the lower limbs to the upper body, leading to underdevelopment of the lower extremities.

Clinical Features

The primary feature of sirenomelia is the fusion of the lower limbs. The degree of fusion can vary, ranging from complete fusion with a single foot to partial fusion with two distinct feet. Other common features include:

Absence or underdevelopment of the genitalia and urinary tract
Anomalies of the gastrointestinal tract, such as imperforate anus
Renal agenesis or dysgenesis
Skeletal abnormalities, including sacral agenesis

Diagnosis

Sirenomelia can often be diagnosed prenatally through ultrasound imaging, which may reveal the characteristic limb fusion and associated anomalies. Postnatal diagnosis is based on physical examination and imaging studies such as X-ray and MRI to assess the extent of the malformations.

Management

There is no cure for sirenomelia, and management focuses on addressing the associated anomalies and improving the quality of life. Surgical interventions may be necessary to correct gastrointestinal and genitourinary malformations. In some cases, separation of the fused limbs may be attempted, although this is complex and depends on the individual anatomy.

Prognosis

The prognosis for individuals with sirenomelia is generally poor, with a high rate of stillbirth or early neonatal death due to severe malformations, particularly of the renal and respiratory systems. However, there have been rare cases of long-term survival with extensive medical and surgical management.

Related pages

@@ Line 1: / Line 1: @@
-== Sirenomelia ==
+{{Short description|A rare congenital malformation characterized by fused lower limbs}}
+{{Medical condition}}
-[[File:Sirenomelia2.jpg|thumb|upright|Sirenomelia]]
+'''Sirenomelia''', also known as '''mermaid syndrome''', is a rare congenital developmental disorder characterized by anomalies of the lower spine and lower limbs. The condition results in the fusion of the legs, giving the appearance of a mermaid's tail, hence the name. Sirenomelia is associated with a range of other malformations, particularly affecting the [[genitourinary system]], [[gastrointestinal tract]], and [[skeletal system]].
-'''Sirenomelia''', also called '''mermaid syndrome''', is a rare [[congenital deformity]] in which the legs are fused together, giving the appearance of a [[mermaid]]'s tail, hence the nickname.
+==Epidemiology==
+Sirenomelia is an extremely rare condition, with an estimated incidence of 1 in 100,000 live births. It is more common in males than females, with a male-to-female ratio of approximately 3:1. The condition is often associated with [[maternal diabetes]], which is considered a significant risk factor.
-<youtube>
+==Pathophysiology==
-title='''{{PAGENAME}}'''
+The exact cause of sirenomelia is not well understood, but it is believed to result from a disruption in the normal development of the caudal region of the embryo. This disruption may be due to abnormal vascular supply, specifically the "steal phenomenon," where the blood supply is diverted from the lower limbs to the upper body, leading to underdevelopment of the lower extremities.
-movie_url=http://www.youtube.com/v/QWbea6sAWp0
-&rel=1
-embed_source_url=http://www.youtube.com/v/QWbea6sAWp0
-&rel=1
-wrap = yes
-width=750
-height=600
-</youtube>
-== Etymology ==
+==Clinical Features==
-The word ''sirenomelia'' derives from the ancient Greek word ''seirēn,'' referring to the mythological [[Siren (mythology)|Sirens]], who were sometimes depicted as mermaids, and ''melos'', meaning "limb".
+The primary feature of sirenomelia is the fusion of the lower limbs. The degree of fusion can vary, ranging from complete fusion with a single foot to partial fusion with two distinct feet. Other common features include:
-== Description ==
+* Absence or underdevelopment of the [[genitalia]] and [[urinary tract]]
-Sirenomelia is mainly characterized by the fusion of both legs with rotation of the [[fibula]]. It may include absence of the lower spine, abnormalities of the pelvis, renal organs, and was previously thought to be a severe form of sacral agensis/caudal regression syndrome, but more recently research verifies that these two conditions are not related.<ref>reference: https://rarediseases.org/rare-diseases/sirenomelia/ and Das BB, Rajegowda BK, Bainbridge R, Giampietro PF. Caudal regression syndrome versus sirenomelia: a case report. J Peritnatol. 2002;22:169-170)</ref> NORD has a separate report on caudal regression syndrome. In general, the more severe cases of limb fusion correlate with more severe dysplasia in the pelvis. Rather than the two iliac arteries present in fetuses with complete renal agenesis, fetuses with sirenomelia display no branching of the [[abdominal aorta]], which is always absent.<ref name=":1">{{Cite book|url=https://www.worldcat.org/oclc/751694637|title=Common malformations.|last=B.|first=Holmes, Lewis|date=2011|publisher=Oxford University Press, USA|isbn=9780199722785|location=Oxford|oclc=751694637}}</ref>
+* Anomalies of the [[gastrointestinal tract]], such as imperforate anus
+* [[Renal agenesis]] or dysgenesis
+* [[Skeletal abnormalities]], including [[sacral agenesis]]
-Associated defects recorded in cases of sirenomelia include [[neural tube defect]]s ([[rachischisis]], [[anencephaly]], and [[spina bifida]]), [[holoprosencephaly]], [[hypoplastic left heart syndrome]], other heart defects, [[esophageal atresia]], [[omphalocele]], [[intestinal malrotation]], [[persistent cloaca]], and other limb defects (most commonly absence of the radius).<ref name=":1" />
+==Diagnosis==
+Sirenomelia can often be diagnosed prenatally through [[ultrasound]] imaging, which may reveal the characteristic limb fusion and associated anomalies. Postnatal diagnosis is based on physical examination and imaging studies such as [[X-ray]] and [[MRI]] to assess the extent of the malformations.
-== Diagnosis ==
+==Management==
-Though obvious at birth, sirenomelia can be diagnosed as early as 14 weeks gestation on  [[Obstetric ultrasonography|prenatal ultrasound]]. When there is low amniotic fluid around the fetus ([[oligohydramnios]]), the diagnosis is more difficult.<ref name=":1" />
+There is no cure for sirenomelia, and management focuses on addressing the associated anomalies and improving the quality of life. Surgical interventions may be necessary to correct gastrointestinal and genitourinary malformations. In some cases, separation of the fused limbs may be attempted, although this is complex and depends on the individual anatomy.
-== Causes ==
+==Prognosis==
-The ultimate cause of sirenomelia is a subject of debate.The first hypothesis of its origin was developed in 1927 and proposed that a lack of blood supply to the lower limbs during their development is responsible for the defect. This "vascular steal" hypothesis was developed in response to the observed absence or severe underdevelopment of the aorta below the umbilical artery, which "steals" the blood supply from the lower limbs. Other hypotheses involve an insult to the embryo between 28–32 days affecting the [[Mesoderm|caudal mesoderm]], a [[teratogen]] exposure affecting the neural tube during [[neurulation]], and a defect in the twinning process that either stops the process of caudal differentiation or generates a second [[primitive streak]].<ref name=":1" />
+The prognosis for individuals with sirenomelia is generally poor, with a high rate of stillbirth or early neonatal death due to severe malformations, particularly of the renal and respiratory systems. However, there have been rare cases of long-term survival with extensive medical and surgical management.
-Maternal [[diabetes mellitus]] has been associated with [[caudal regression syndrome]] and sirenomelia,<ref>{{Cite book|url=https://www.worldcat.org/oclc/965492903|title=Emery's elements of medical genetics|last=Peter D.|first=Turnpenny|publisher=Elsevier|others=Ellard, Sian,|year=2017|isbn=9780702066894|edition= Edition 15|location=[Philadelphia, Pa.]|pages=|oclc=965492903}}</ref><ref>{{cite book|url=https://books.google.com/books?id=qsQWI-v50MwC&pg=PA217&dq=sirenomelia+%22maternal+diabetes%22+incidence|title=Rudolph's Fundamentals of Pediatrics|author1=Abraham M. Rudolph|author2=Robert K. Kamei|author3=Kim J. Overby|publisher=McGraw Hill|year=2002|isbn=978-0-8385-8450-7|page=217|accessdate=2008-04-21}}{{vs|does page 217 really say something about the relationship between sirenomelia and maternal diabetes?|date=November 2012}}</ref> although a few sources question this association.<ref>{{cite journal|last1=Assimakopoulos|first1=E|last2=Athanasiadis|first2=A|last3=Zafrakas|first3=M|last4=Dragoumis|first4=K|last5=Bontis|first5=J|year=2004|title=Caudal regression syndrome and sirenomelia in only one twin in two diabetic pregnancies|journal=Clinical and experimental obstetrics & gynecology|volume=31|issue=2|pages=151–3|pmid=15266776}}</ref> Prenatal [[cocaine]] exposure has also been suggested as an association with sirenomelia.<ref name=":1" />
+==Related pages==
+* [[Congenital disorder]]
-=== Genetics ===
+* [[Caudal regression syndrome]]
-In animal models, several genes have been found to cause or be associated with sirenomelia. The ''srn'' (''siren'') gene is observed to cause hindlimb fusion in homozygous mice.<ref name=":1" /><ref>{{Cite web|url=https://www.ncbi.nlm.nih.gov/gene/20812|title=srn siren [ Mus musculus (house mouse) ]|last=|first=|date=|website=NCBI Gene|archive-url=|archive-date=|dead-url=|access-date=}}</ref> Mice with knockouts or mutations in both ''[[tsg1]]'' and ''[[Bone morphogenetic protein 7|bmp7]]'' will also have hindlimb fusion.<ref name=":1" /><ref>{{Cite web|url=https://www.ncbi.nlm.nih.gov/gene/65960|title=Twsg1 twisted gastrulation BMP signaling modulator 1 [ Mus musculus (house mouse) ]|last=|first=|date=|website=NCBI Gene|archive-url=|archive-date=|dead-url=|access-date=}}</ref><ref>{{Cite web|url=http://www.informatics.jax.org/marker/MGI:98421|title=srn MGI Mouse Gene Detail - MGI:98421 - siren|website=www.informatics.jax.org|access-date=2018-10-19}}</ref>
+* [[VACTERL association]]
-== Classification ==
-[[File:Sirenomelia.svg|left|thumb|Classification of sirenomelia by the presence or absence of bones within the lower limb.<br>
-I) all bones of thigh and lower leg present<br>
-II) fused [[fibula]]<br>
-III) fibula absent<br>
-IV) partially fused femur, fused fibula<br>
-V) partially fused femur<br>
-VI) fused femur, fused [[tibia]]<br>
-VII) fused femur, tibia absent]]Sirenomelia is classified by the skeletal structure of the lower limb, ranging from class I, where all bones are present and only the soft tissues are fused, to class VII where the only bone present is a fused [[femur]].<ref name=":1" />
-It has also been classified as an expanded part of the [[VACTERL association]] and as a form of [[caudal regression syndrome]].<ref name=":1" /><ref>{{cite journal|last1=Onyeije|first1=Chukwuma|last2=Sherer|first2=David|last3=Handwerker|first3=Sara|last4=Shah|first4=Leena|year=2008|title=Prenatal Diagnosis of Sirenomelia with Bilateral Hydrocephalus: Report of a Previously Undocumented form of VACTERL-H Association|journal=American Journal of Perinatology|volume=15|issue=3|pages=193–7|doi=10.1055/s-2007-993925|pmid=9572377}}</ref><ref>{{Cite book|url=https://www.worldcat.org/oclc/828737906|title=Human embryology and developmental biology|last=M.|first=Carlson, Bruce|date=2014|publisher=Elsevier/Saunders|isbn=9781455727971|edition= 5th|location=Philadelphia, Pa.|oclc=828737906}}</ref>
-== Prognosis ==
-Sirenomelia is usually fatal. Many pregnancies with a sirenomelic fetus spontaneously [[Miscarriage|miscarry]]. One-third to one-half of infants are [[Stillbirth|stillborn]], with all but a few dying in the [[neonatal period]].<ref name=":1" />
-In cases of [[monoamniotic twins]] where one is affected, the twin with sirenomelia is protected from [[Potter sequence]] (particularly [[pulmonary hypoplasia]] and abnormal facies) by the normal twin's production of amniotic fluid.<ref name=":0" /><ref name=":1" />
-== Epidemiology ==
-This condition is found in approximately one out of every 100,000 live births; studies produce rates from 1 in 68,741 to 1 in 97,807.<ref name=":1" /><ref name="Kallen">{{cite journal |doi=10.1136/jmg.29.1.30 |title=The cyclops and the mermaid: An epidemiological study of two types of rare malformation |year=1992 |last1=Kallen |first1=B |last2=Castilla |first2=E E |last3=Lancaster |first3=P A |last4=Mutchinick |first4=O |last5=Knudsen |first5=L B |last6=Martinez-Frias |first6=M L |last7=Mastroiacovo |first7=P |last8=Robert |first8=E |journal=Journal of Medical Genetics |volume=29 |pages=30–5 |pmid=1552541 |issue=1 |pmc=1015818}}</ref> It is 100 to 150 times more likely in identical (monozygotic) twins than in singletons or fraternal twins.<ref name=":0">{{Cite book|url=https://www.worldcat.org/oclc/859526325|title=Creasy and Resnik's maternal-fetal medicine : principles and practice|others=Creasy, Robert K.,, Resnik, Robert,, Greene, Michael F.,, Iams, Jay D.,, Lockwood, Charles J.,|isbn=9780323186650|edition= Seventh|location=Philadelphia, PA|oclc=859526325}}</ref><ref name=":1" /> Sirenomelia is not associated with any ethnic background, but fetuses with sirenomelia are more likely to have [[Testicle|testes]].<ref name=":1" /><!-- This is phrased as "more likely to have testes" (or alternatively, gonadal males) specifically because the original studies only assessed presence of ovaries, testes, or neither in affected fetuses/neonates. These studies did not involve karyotyping, and fetuses with sirenomelia typically do not have genitals. -->
-==History==
-Sirenomelia was first reported in 1542. In 1927, Otto Kampmeier discovered the association between sirenomelia and [[single umbilical artery]].<ref name=":1" />
-=== Notable individuals ===
-Only a few individuals who had some functioning kidney tissue have survived the neonatal period.<ref name=":1" />
-==== Tiffany Yorks ====
-Tiffany Yorks of [[Clearwater, Florida]] (May 7, 1988 – February 24, 2016)<ref>{{cite tweet|user=TiffanyYorks|author=Tiffany Yorks|number=702573145534783489|date=24 February 2016|title=This is Tiffanys cousin Jessica Tannehill. Tiffany passed away this morning after a hard fight and she stayed...}}</ref> underwent successful [[surgery]] in order to separate her legs before she was a year old.<ref name="firststeps"/> She was the longest-surviving sirenomelia patient to date.<ref name="legssplit"/> She suffered mobility issues due to her fragile leg bones, and compensated by using crutches or a wheelchair. She died on February 24, 2016 at the age of 27.
-==== Shiloh Pepin ====
-Shiloh Jade Pepin (August 4, 1999 – October 23, 2009) was born in [[Kennebunkport, Maine]], [[United States]] with her lower extremities fused, no bladder, no [[uterus]], no rectum, only 6&nbsp;inches of large [[colon (anatomy)|colon]], no [[vagina]], and with only one quarter of a [[kidney]] and one [[ovary]]. Her parents initially anticipated she could expect only a few months of life. At age 3, her natural kidney failed, and she began [[dialysis]].<ref>TV program ''Body Shock'', 10–11 pm, 18 May 2010, [[Channel 4]]</ref> A [[kidney transplantation|kidney transplant]] at age 2 lasted a number of years, and in 2007 a second kidney transplant was successful. She attended Consolidated [[Elementary School]]. She remained hopeful about her disease and joked often and lived her life happily, despite her challenges, as seen in her [[TLC (TV channel)|TLC]] documentary in "Extraordinary People: Mermaid Girl". Shiloh and her family were debating surgery because of the risks involved, even though it would improve her quality of life. Many people who have this condition receive surgery when they are young, but Shiloh was already 8 years old in the documentary and had not received surgery.  Shiloh was the only one of the three survivors of sirenomelia without surgery for separation of the conjoined legs.<ref name="aolhealth">{{cite web|url=http://www.aolhealth.com/health/mermaid-syndrome-sirenomelia|title=10-Year-Old Girl Born With Legs Fused Together|last=Sammons|first=Mary Beth|date=November 26, 2009|publisher=AOL|archiveurl=https://web.archive.org/web/20091126004109/http://www.aolhealth.com/health/mermaid-syndrome-sirenomelia|archivedate=November 26, 2009}}</ref>  She died of [[pneumonia]] on October 23, 2009, at [[Maine Medical Center]] in [[Portland, Maine]], at the age of 10;<ref>{{cite web|author=Laura Dolce |url=http://www.seacoastonline.com/articles/20091023-NEWS-910239966 |title=Community saddened at 'Mermaid girl' Shiloh Pepin's passing |publisher=SeacoastOnline.com |date=2009-10-23 |accessdate=2011-12-01}}</ref> having appeared on the Oprah Winfrey Show on September 22, 2009.<ref>{{cite web|title=SHILOH PEPIN|url=http://www.oprah.com/oprahshow/In-Memoriam-Remembering-Oprah-Show-Guests/10|work=The Oprah Show|publisher=oprah.com|accessdate=4 March 2014|date=May 16, 2011|quote=In Memoriam: The Oprah Show has hosted a number of unforgettable guests over the years. Look back at some of those who are no longer with us.}}</ref> Shiloh gained a following of admirers by documenting her condition on [[TV]], [[Facebook]], and the [[Internet]].
-==== Milagros Cerrón ====
-Milagros Cerrón Arauco was born on April 27, 2004, in [[Huancayo]], [[Peru]]. Although most of Milagros’ internal organs, including her heart and lungs, are in perfect condition, she was born with serious internal defects, including a deformed left [[kidney]] and a very small right one located very low in her body. In addition, her [[gastrointestinal tract|digestive]], [[urinary system|urinary tract]]s and [[sex organ|genitals]] share a single tube.
-This birth defect occurs during the gastrulation week (week 3) of embryonic development. Gastrulation establishes the three germ layers: ectoderm, mesoderm and endoderm. It seems that complications such as defects in the urogenital system as mentioned above can be possibly due to malformations in the intermediate mesoderm.
-A four-hour operation to insert silicone bags between her legs to stretch the skin was successfully completed on February 8, 2005. A successful operation to separate her legs to just above the knee took place May 31, 2005, in a "Solidarity Hospital" in the district of [[Surquillo]] in [[Lima]]. The procedure, however, was so intensive that she became [[Psychological trauma|traumatized]] to the degree of losing her ability to form proper speech patterns, leaving her nearly [[speech disorder|mute]]. It is not yet known if this is a [[physiological]] or [[psychological]] condition. However, at Milagros' second birthday, her mother reported that she knew more than 50 words. A second operation to complete the separation up to the groin took place on September 7, 2006.<ref name="legssplit">{{cite web|url=http://news.bbc.co.uk/1/hi/health/5325082.stm|title="Mermaid" girl's legs separated|date=7 September 2006|publisher=BBC News}}</ref>
-Her doctor Luis Rubio said he was pleased with the progress Milagros had made, but cautioned that she still needed 10 to 15 years of rehabilitation and more operations before she could lead a normal life. Particularly, she will require reconstructive surgery to rebuild her rudimentary [[anus]], [[urethra]] and genitalia.
-Milagros' parents are from a poor village in Peru's [[Andes|Andes Mountains]]; the Solidarity Hospital has given a job to her father Ricardo Cerrón so that the family can remain in [[Lima]], while the City of Lima has pledged to pay for many of the operations.<ref name="firststeps">{{cite web|url=http://news.bbc.co.uk/2/hi/americas/5381616.stm|title="Mermaid" girl takes first steps|publisher=BBC News|date=28 September 2006}}</ref>
-==References==
-{{Reflist}}
-{{Medical resources
-|   DiseasesDB     =
-|   ICD10          = {{ICD10|Q|87|2|q|80}}
-|   ICD9           = {{ICD9|759.89}}
-|   ICDO           =
-|   OMIM           =
-|   MedlinePlus    =
-|   eMedicineSubj  =
-|   eMedicineTopic =
-|   MeshID         = D004480
-}}
-{{Phakomatoses and other congenital malformations not elsewhere classified}}
 [[Category:Congenital disorders]]
 [[Category:Rare diseases]]
-[[Category:Mermaids]]
-{{stub}}