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Classification and external resources
ICD-10 Q87.2
ICD-9 759.89
eMedicine / 
MeSH [1]

Sirenomelia, alternatively known as mermaid syndrome is a very rare congenital deformity in which the legs are fused together, giving the appearance of a mermaid's tail.

This condition is found in approximately one out of every 100,000 live births[1] (about as rare as conjoined twins) and is usually fatal within a day or two of birth because of complications associated with abnormal kidney and bladder development and function. It results from a failure of normal vascular supply from the lower aorta in utero. Maternal diabetes has been associated with caudal regression syndrome and sirenomelia,[2] although this association is not generally accepted.[3]

VACTERL-H is an expanded form of the VACTERL association that concludes that this diagnosis is a less severe form of sirenomelia.[4] The disorder was formerly thought to be an extreme case of Caudal regression syndrome; however, it was reclassified to be considered a separate condition.

Notable cases

Only a handful of patients who did not have the usual kidney and bladder complications have survived this condition, three of them being:

Milagros Cerrón (Age 5)

Milagros Cerrón Arauco (born 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 digestive, urinary tracts and genitals share a single tube. This birth defect occurs during the gastrulation week (week 3) of embyrological development. Gastrulation establishes the three derm 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 traumatized to the degree of losing her ability to form proper speech patterns, leaving her nearly mute. As yet it is not known if this is a physiological or psychological condition. However, at Milagros's 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.[5] A few weeks later, she took her first steps.[6]

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 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.[7]

Tiffany Yorks (Age 21)

Tiffany Yorks of the United States (born May 7, 1988) underwent successful surgery in order to separate her legs. She is the longest-surviving sirenomelia patient to date.

Shiloh Pepin (Age 10)

Shiloh Pepin was born in Kennebunkport, Maine in August, 1999, with her lower extremities fused, a missing bladder, uterus, colon and vagina, with only one partial kidney and one ovary. Her parents initially anticipated she could expect only a few months of life. An initial kidney transplant at 4 months of age, lasted a number of years, and in 2007 a second kidney transplant was successful. She attends Consolidated Elementary School. Shiloh is the only one of the three survivors of sirenomelia without surgery for separation of the conjoined legs.


  1. ^ Kallen B, Castilla EE, Lancaster PA, Mutchinick O, Knudsen LB, Martinez-Frias ML, Mastroiacovo P, Robert E (1992). "The cyclops and the mermaid: an epidemiological study of two types of rare malformation". J Med Genet 29 (1): 30–5. doi:10.1136/jmg.29.1.30. PMID 1552541. 
  2. ^ Abraham M. Rudolph, Robert K. Kamei and Kim J. Overby. ""Rudolph's Fundamentals of Pediatrics"". McGraw Hill Professional 2002, ISBN 0838584500.,M1. Retrieved on 2008-04-21. 
  3. ^ Oneije C. I., Sherer D. M., Handwerker S. and Shah L.. ""Caudal Regression Syndrome and Sirenomelia in Only One Twin in Two Diabetic Pregnancies"". Clinical and Experimental Obstetrics and Gynecology 31: 151-3; 2004. Retrieved on 2008-04-17. 
  4. ^ E Assimakopoulos, A Athanasiadis, M Zafrakas, K Dragoumis and J Bontis. ""Prenatal diagnosis of sirenomelia with bilateral hydrocephalus : Report of a previously undocumented form of VACTERL-H association"". American journal of perinatology 15: 193-97; 1998. Retrieved on 2008-04-21. 
  5. ^ BBC News 24, September 7, 2006,"Mermaid" girl's legs separated;
  6. ^ Daily Mail September 27, 2006, "Mermaid" girl takes her first unaided steps;
  7. ^ BBC News September 28, 2006, "Mermaid" girl takes first steps;