Rare Endocrinology News

Disease Profile

Sirenomelia

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.
<1 / 1 000 000

< 331

US Estimated

< 514

Europe Estimated

Age of onset

Neonatal

ICD-10

Q87.2

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

Mermaid malformation; Fused legs and feet; Sirenomelus;

Categories

Congenital and Genetic Diseases; Digestive Diseases; Kidney and Urinary Diseases

Summary

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]

Symptoms

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Absence of the sacrum
0010305
Ambiguous genitalia
Ambiguous external genitalia
Ambiguous external genitalia at birth
Intersex genitalia

[ more ]

0000062
Anal atresia
Absent anus
0002023
Renal hypoplasia/aplasia
Absent/small kidney
Absent/underdeveloped kidney

[ more ]

0008678
Sirenomelia
0010497
30%-79% of people have these symptoms
Abnormality of the cardiovascular system
Cardiovascular abnormality
0001626
Aplasia/Hypoplasia of the radius
0006501
Spina bifida
0002414
Tracheoesophageal fistula
0002575
Percent of people who have these symptoms is not available through HPO
Anterior sacral meningocele
0007293
Autosomal dominant inheritance
0000006
Back pain
0003418
Constipation
0002019
Dermoid cyst
0025247
Headache
Headaches
0002315
Hemisacrum
0009790
Meningitis
0001287
Meningocele
0002435
Neurogenic bladder
Lack of bladder control due to nervous system injury
0000011
Rectal abscess
0005224
Sacral lipoma
0012033
Urinary retention
0000016

Cause

The exact cause of sirenomelia is unknown. Researchers believe that both environmental and genetic factors may play a role (multifactorial). Some cases are thought to result from irregularities in early development of the circulatory system, as some individuals with sirenomelia have a single large artery branching off of the aorta (instead of the usual two). Abnormalities in this blood delivery system decreases blood flow to the lower areas of the embryo, interfering with development.[1] Some of the risk factors that have been identified in this condition include maternal diabetes, teratogens, genetic factors and maternal age younger than 20 years.[2]

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a 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.

References

Rare Endocrinology News