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Year : 2002  |  Volume : 12  |  Issue : 3  |  Page : 399-401
Sirenomelia sequence (mermaid) : Report of three cases

Dept of Radiology, Govt. Medical College, Nagpur, India

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Keywords: Sirenomelia, caudal regression syndrome, mermaid

How to cite this article:
Taori K B, Mitra K, Ghonga N P, Gandhi R O, Mammen T, Sahu J. Sirenomelia sequence (mermaid) : Report of three cases. Indian J Radiol Imaging 2002;12:399-401

How to cite this URL:
Taori K B, Mitra K, Ghonga N P, Gandhi R O, Mammen T, Sahu J. Sirenomelia sequence (mermaid) : Report of three cases. Indian J Radiol Imaging [serial online] 2002 [cited 2020 Aug 8];12:399-401. Available from:
Sirenomelia Sequence [Mermaid] is a congenital structural anomaly characterized by an abnormal development of the caudal region of the body with different degrees of fusion of the lower extremities and bears resemblance to the mermaid of Greek mythology. This deformity is also known as Symmelia, Symposia, Sympus, Uromelia and Monopodia. Sirenomelia has a prevalence of two to three cases per one lakh births with male: female ratio of 3:1. About 300 cases have been reported in the world literature so far of which eight have been reported in India. We report here three cases of mermaid syndrome one of which is remarkable in complete absence of the genito-urinary system

   Case 1: Top

A Twenty two years old primigravida, positive for cytomegalovirus and rubella, delivered a 1.5 kg baby vaginally. The Baby cried weakly after birth and survived for twelve hours. There was no history of medication in the early pregnancy. The patient had not undergone any USG examination during her pregnancy.

Physical examination of the infant showed complete fusion of the non rotated lower limbs with one toe and five digits while the upper limb showed radial deviation of the wrist with four digits (thumb being absent), absence of external genitalia, urogenital and anal orifices. [Figure - 1],[Case1]

Radiograph of the infant showed rudimentary iliac bones, sacral agenesis, spina bifida, absent radii bilaterally, complete fusion of the femur with modelling deformity, two tibia, one fibula, five digits and thirteen ribs. [Figure - 2],[Case1]

USG abdomen of the infant showed a longitudinal reniform hypoechoic structure with lobulated surface and echogenic interior in both renal fossa. The Hilum was not present. The Bladder or rectum could not be visualized.

Autopsy revealed complete absence of the genitourinary system with hypertrophied adrenals occupying the renal fossa bilaterally. Kidneys, ureters and bladder were absent. [Figure - 3],[Case 1]. The Midgut loop was blindly ending and the rectum was absent. The Gall Bladder was found without a cystic duct with no communication with the duodenum. The Lungs were non-inflated and the heart was normal. There was a single umbilical artery which arose directly from the aorta high in the abdominal cavity, with tapering and hypoplasia of the aorta and its branches distal to the origin of the umbilical artery.

   Case 2: Top

A Twenty years old second gravida delivered a 1.4 kg baby vaginally who died immediately after birth. She had a history of treatment for malaria during her early pregnancy. She did not undergo any USG examination during her pregnancy.

Physical Examination of the infant showed a short neck, indeterminate sex, absent external genitalia, urogenital and anal orifice and completely fused non-rotated lower limbs without feet.

Radiograph of the infant revealed absence of all foot bones, absent fibula bilaterally with two tibia and fused femur showing modelling deformity. Sacrum was absent with rudimentary iliac bones. Thoraco-lumbar kypho-scoliosis was present with deformed ribs and cervical vertebrae. Left clavicle was absent. Due to cultural constraints the autopsy could not be done. [Figure - 4],[Case 2]

   Case 3: Top

A Twenty-five years old primigravida delivered a 1.3 kg stillborn baby vaginally. She did not give any history of medication during her early pregnancy and did not undergo any ultrasound examination during her pregnancy.

Physical Examination of the infant showed complete fusion of the lower limbs with one toe. There was absence of the external genitalia, urogenital and anal orifices.

Radiograph of the infant showed two femur, two tibia, absent fibula with two digits and sacral agenesis. Spine and skull were normal. Due to cultural constraints the autopsy could not be done [Figure - 5],[Case3]

   Discussion Top

Sirenomelia has been classified into three types

a) Simpus Apus: No feet, one tibia, one femur

b) Simpus Unipus: One foot, two femur, two tibia, two fibula

c) Simpus Dipus: Two feet and two fused legs (flipper like)-this is called a mermaid.

The precise etiology of sirenomelia is not well understood. Many theories have been proposed but none of these is considered conclusive. It has been reported to occur as a result of the use of teratogenic agents. Hibelink et al [1] demonstrated that the intravenous administration of cadmium and lead can produce sirenomelia in the golden hamster. VonLennep et al [2] described the possible teratogenic effects of Vitamin A. Duhemmel et al [3] consider this anomaly as a manifestation of the caudal regression syndrome that is a consequence of abnormal development of structures derived from the caudal mesoderm of the embryo before the fourth week of gestation and extended to various cranio-caudal levels. Maternal diabetes mellitus, genetic predisposition and vascular hypoperfusion have been proposed as possible causative factors. In 1973, Quan and Smith [4] proposed the term VATER to denote non-random association of vertebral defects, anorectal anomalies and tracheo-esophageal fistula, with renal and radial limb defects. Lately, many authors have drawn attention to the overlap in phenotypic manifestations of sirenomelia and VATER [5],[6]. In 1987 Stocker and Heifetz [7] proposed the defect in the primitive streak as a causative factor. Stevenson [8] proposed the vitelline artery steal theory. They reported that in each of the eleven sirenomelia specimens, a large artery arose from the aorta high in the abdomen beyond which the aorta and its branches were hypoplastic. They inferred that the vitelline artery steals blood and nutrients away from the caudal part of the embryo. But Jaiyesimi and Gomthinarayan recently reported a case where a single umbilical artery arose normally from the common iliac artery.

Prenatal diagnosis of sirenomelia is possible by demonstrating the fused femur, decreased distance between two femur and decreased or absent mobility of the two lower limbs with respect to each other. On physical examination of the infant, the defect varies from simple cutaneous fusion of the limbs to absence of all long bones except fused femur. Radiograph of the infant shows the exact bony anomaly while USG abdomen can demonstrate the solid viscera. Thus it is a universally lethal entity and prenatal diagnosis on USG is desired so that termination of pregnancy can be offered at the earliest.

   References Top

1.Hibelink DR, Kaplan. Sirenomelia: analysis in the cadmium and lead treated golden hamster. Teratology carcinog 1986; 6: 431-440.  Back to cited text no. 1    
2.Von Lennep E, Elkhazen, De Pierreux. A case of partial Sirenomelia and possible vitamin A teratogenesis Prenatal Diagnosis 1985; 5: 35-40.  Back to cited text no. 2    
3.Duhamel B. From the mermaid to anal imperforation: the syndrome of caudal regression. Arch Dis Child 1964; 36: 152-155.  Back to cited text no. 3    
4.Quan L and Smith DW. The VATER association: vertebral defects, anal atresia, tracheo-esophageal fistula with esophageal atresia, renal and radial dysplasia: a spectrum of associated defects J. Pediatr 1973; 82: 104-107.  Back to cited text no. 4    
5.Duncan PA, Shapiro LR, Klien RM. Sacrococcygeal dysgenesis association Am J Med. Genet. 1991; 41: 153-161.  Back to cited text no. 5    
6.Schuler L, Salzano FM. Patterns in multimalformed babies and the question of relationship between sirenomelia and VACTERL. Am J. Med. Genet. 1994; 49: 29-35.  Back to cited text no. 6    
7.Stoker JT: Heifetz SA. Sirenomelia: morphological study of 33 cases and review of literature. Perspect Pediatr Pathol 1987; 10: 7-50.  Back to cited text no. 7    
8.Stevenson RE, Johnes KL, Phelan MC; Jones MC; Barr M; Clericuzio C et al. Vascular steal: the pathogenetic mechanism producing sirenomelia and associated defects of the viscera and soft tissues. Pediatrics 1986; 78: 451-457.  Back to cited text no. 8    

Correspondence Address:
K B Taori
Dept of Radiology, Govt. Medical College, Nagpur
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Source of Support: None, Conflict of Interest: None

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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]

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