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Genetic and Rare Diseases Information Center (GARD)

Other Names for this Disease
  • Fused legs and feet
  • Mermaid malformation
  • Mermaid syndrome
  • Sirenomelia sequence
  • Sirenomelus
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Sirenomelia is a birth defect in which affected infants are born with a single lower extremity or with two legs that are fused together. The symptoms and physical findings associated with the condition vary greatly among affected individuals and may include malformations of the spine and skeletal system (commonly with vertebrae either absent or defective); absent or underdeveloped internal and external sex organs, rectum, kidneys and/or bladder; closed rectal opening (imperforate anus); and other abnormalities of the lower gastrointestinal tract. The exact cause is unknown, but it is believed to result from irregularities in early development of the blood circulating system within the embryo. Surgery has been successful in separating joined legs. Other treatment is symptomatic and supportive.[1]
Last updated: 5/4/2011


  1. Sirenomelia Sequence. NORD. 2002; Accessed 5/4/2011.
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Please contact us with your questions about Sirenomelia. We will answer your question and update these pages with new resources and information.

Basic Information

  • The National Organization for Rare Disorders (NORD) is a federation of more than 130 nonprofit voluntary health organizations serving people with rare disorders. Click on the link to view information on this topic.

In Depth Information

  • The Online Mendelian Inheritance in Man (OMIM) is an catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Sirenomelia. Click on the link to view a sample search on this topic.