Sirenomelia: a case report

Objective

It is aimed in this study to  evaluate the characteristics of a case of sirenomelia diagnosed at our obstetrics department.

Case(s)

A 23 years old woman (G2P1) with an intrauterine pregnancy of 35 weeks of pregnancy referred to our clinic with a cervical dilatation of 9 cm and delivered a baby (2,600 g and 1st and 5th minutes of Apgar scores of 3-0) with fetal anomalies such as single lower extremities, rudimentary foot and external genitalia which are in the shape of a small bud. The upper extremities and anal hiatus were normal. The initial diagnosis of the baby was sirenomelia. Autopsy also confirmed the diagnosis of sirenomelia. There were undeveloped bone pelvis, single lower extremities, fusion of the femur bones, rudimentary tibia bones and absence of fibulas. Urinary bladder, ureter and urethra were absent, and rectum was atresic. On microscopic evaluation there was haemorrhage at lungs, liver, heart and kidney. The placenta and umbilical cord were normal.   

Conclusion

Sirenomelia is a rare and lethal congenital anomaly. It is important to diagnose this anomaly in order to give counseling to the family for termination of the pregnancy.

Keywords

Sirenomelia, congenital malformations, autopsy

Introduction

Sirenomelia is a congenital anomaly seen in 1 out of 60,000 -100,000.[1] The rate of male/female fetus is 2.7/1 and it is prevalent among monozygotic twins.[2] Sirenomelia is defined as a lethal anomaly in which severe urogenital malformations are seen together with the fusion, rotation and hypotrophy of lower extremities.[3] This anomaly may be a variant of caudal regression syndrome (CRS); however, it is distinguished by the presence of two umbilical arteries and non-lethal renal anomalies, non-existence of the fusion of lower extremities and tracheoesophageal, neural tube and cardiac anomalies.[4] In this study, our purpose is to evaluate the characteristics of sirenomelia case which was established intrapartum diagnosis and delivered in our clinic. 

Case(s)

Twenty-three-year-old woman (G2P1) with an intrauterine pregnancy of 35 weeks of pregnancy referred to our clinic with a cervical dilatation of 9 cm. There was no prominent characteristic in her obstetric history and it was observed that she had a kin marriage. It was found in her family history that one of her second degree relatives delivered a baby with anencephaly and another relative had two deliveries which were neural tube defects. The patient delivered by normal vaginal way and delivered a baby with fetal anomalies (2,600 g and 1st and 5th minutes of Apgar scores of
3-0). The anomalies of the baby were single and attached lower extremities, rudimentary foot and undeveloped external genitalia which are in the shape of a small bud. Upper extremities and anal hiatus were normal. Initial diagnosis of the baby was sirenomelia. Autopsy also confirmed the diagnosis of sirenomelia. There were undeveloped bone pelvis, single lower extremities, fusion of the femur bones, rudimentary tibia bones, and absence of fibulas. Urinary bladder, ureter and urethra were absent, and rectum was atresic (Figures 1 and 2). On microscopic evaluation, there was haemorrhage at lungs, liver, heart and kidney. The placenta and umbilical cord were normal. No sacral agenesia, hypoplastic fetus, combined femur and tibia, and absence of fibula were detected in the postpartum radiography (Figure 3). 

Discussion

Sirenomelia is a congenital anomaly seen in 1 out of 60,000 -100,000[1] and is defined as a lethal anomaly in which severe urogenital malformations are seen together with the fusion, rotation and hypotrophy or atrophy of lower extremities.[3]
Maternal diabetes and genetic predisposition are the predisposing factors for sirenomelia.[5,6] Only five sirenomelia cases which lived were defined in the English literature.[7] Pathogenesis of sirenomelia is still not known; only maternal disease known as associated with sirenomelia is diabetes mellitus.[8] In our case, there was no evidence related with diabetes mellitus. It was reported that defects similar to sirenomelia appeared after the exposure to etretinate (synthetic vitamin A analogue) and ochratoxin (fungal toxin) applied on animals experientially.[9,10] In our case, antenatal was free of problems and there was no medical/surgical disease history or medication history.
The existence of anencephaly and neural tube defect in family history of our case makes us to consider that the etiology is genetic; however, genetic analysis was not performed since the family did not accept it. A prenatal ultrasonography including oligohydramnios, malformed lower extremities and normal upper extremities, and single umbilical artery should cause clinician to suspect in favor of sirenomelia. Oligohydramnios is caused by renal agenesia and it generally occurs during second trimester.[11]

Conclusion

Sirenomelai is a rare congenital anomaly. Since it is a lethal anomaly, counseling may be provided to the family for termination of pregnancy in case of an early perinatal diagnosis.

References

1. Duhamel B. From the mermaid to anal imperforation: the syndrome of caudal regression. Arch Dis Child 1961;36:152-5.
2. Murphy JJ, Fraser GC, Blair GK. Sirenomelia: case of the surviving mermaid. J Pediatr Surg 1992;27:1265-8.
3. Schiesser M, Holzgreve W, Lapaire O, Willi N, Lüthi H, Lopez R, Tercanli S. Sirenomelia, the mermaid syndrome--detection in the first trimester. Prenat Diagn 2003;23:493-5.
4. Das BB, Rajegowda BK, Bainbridge R, Giampietro PF. Caudal regression syndrome versus sirenomelia: a case report. J Perinatol 2002;22:168-70.
5. Al Kaissi A, Klaushofer K, Grill F. Caudal regression syndrome and popliteal webbing in connection with maternal diabetes mellitus: a case report and literature review. Cases J 2008;1:407.
6. Aslan H, Yanik H, Celikaslan N, Yildirim G, Ceylan Y. Prenatal diagnosis of caudal regression syndrome: a case report. BMC Pregnancy Child 2001;1:8.
7. Messineo A, Innocenti M, Gelli R, Pancani S, Lo Piccolo R, Martin A. Multidisciplinary surgical approach to a surviving infant with sirenomelia. Pediatrics 2006;118:e220-3.
8. Twickler D, Budorick N, Pretorius D, Grafe M, Currarino G. Caudal regression versus sirenomelia: Sonographic clues. J Ultrasound Med 1993;12:323-30.
9. Von Lennep E, El Khazen N, De Pierreux G, Amy JJ, Rodesch F, Van Regemorter N. A case of partial sirenomelia and possible vitamin A teratogenesis. Prenat Diagn 1985;5: 35-40.
10. Wei X, Sulik KK. Pathogenesis of caudal dysgenesis/ sirenomelia induced by ochratoxin A in chick embryos. Teratology 1996;53:378-91.
11. Valenzano M, Paoletti R, Rossi A, Farinini D, Garlaschi G, Fulcheri E. Sirenomelia. Pathological features, antenatal ultrasonographic clues, and a review of current embryogenic theories. Hum Reprod Update 1999;5:82-6.

	File/Dsecription
	Fig 1. Dorsal view of the infant, with caudal regression and fusion of lower extremities
	Fig 2. Frontal view of the infant, with fusion of the lower extremities and typical face of sirenomelia
	Fig 3. Postmortem radiograph showed sacral agenesis, hypoplastic pelvis, fused lower extremities with paired femurs and tibias and absent fibula