Mermaid Syndrome – A Rare Congenital Anomaly

Mermaid Syndrome
Posterior view of a neonate with mermaid syndrome.

Case of rare congenital anomaly in 19-year-old’s first born

Mermaid syndrome, also known as sirenomelia is an extremely rare anomaly with an incidence of 1 in 100,000 births. In this condition the legs of newborns are joined together, with a mermaid-like appearance, hence the name. Mermaid syndrome has a high morbidity rate with deaths reported shortly after birth. This article describes the case of a 19-year-old’s first neonate born with mermaid syndrome.

The mother’s medical history was significant for gestational diabetes mellitus. The infant was born with thumb anomalies, a single lower limb and ambiguous genitalia. A single umbilical artery, gastrointestinal and urogenital anomalies are common outcomes of this syndrome. Although the cause of the condition is still unknown, there are certain factors, for example, age of the mother younger than 20 years and older than 40 years and exposure of the fetus to teratogenics that increase the risk of mermaid syndrome.

Mermaid syndrome, an evolutionary defect in the caudal region

The rare congenital anomaly causes an evolutionary defect in the caudal region, near the tail or posterior part of the body, with complete absence of the lower limb and varying degree of leg adhesion. The earliest evidence of the syndrome dates back to the 16th century. And since then, only 300 patients have been reported of the rare anomaly. The syndrome is more prevalent in males compared to females, with a ratio of 3:1. Whereas in monozygotic twins the incidence is seen to be 150 to 200 times. It is also 200 times more likely to be seen in newborns with diabetic mothers, as in this case. 15 percent of the mother who gave birth to neonates with mermaid syndrome had gestational diabetes mellitus during pregnancy.

The neonate dies 4 days after birth, owing to the multiple anomalies and perforated anus.

As stated above, although, researchers don’t exactly know what causes the syndrome, there are multiple contributing factors which may vary among different people. It may be because of a genetic predisposition, environmental triggers or vulnerability to the condition. Researchers also believe that in some cases of mermaid syndrome, something has gone wrong in the development of the circulatory system.


Mermaid Syndrome: A Case Report of a Rare Congenital Anomaly in Full-Term Neonate with Thumb Deformity

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Dr. Aiman Shahab is a dentist with a bachelor’s degree from Dow University of Health Sciences. She is an experienced freelance writer with a demonstrated history of working in the health industry. Skilled in general dentistry, she is currently working as an associate dentist at a private dental clinic in Karachi, freelance content writer and as a part time science instructor with Little Medical School. She has also been an ambassador for PDC in the past from the year 2016 – 2018, and her responsibilities included acting as a representative and volunteer for PDC with an intention to make the dental community of Pakistan more connected and to work for benefiting the underprivileged. When she’s not working, you’ll either find her reading or aimlessly walking around for the sake of exploring. Her future plans include getting a master’s degree in maxillofacial and oral surgery, settled in a metropolitan city of North America.


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