Siamese twins: Thoracopagus – A rare congenital anomaly

Insha Khan; Mohd Ilyas; Shariq Ahmad Shah; Cimona Lyn Saldanha

doi:10.4103/jmgims.jmgims_60_17

CASE REPORT

Year : 2020 | Volume : 25 | Issue : 2 | Page : 116-118

Siamese twins: Thoracopagus – A rare congenital anomaly

Insha Khan¹, Mohd Ilyas², Shariq Ahmad Shah², Cimona Lyn Saldanha¹
¹ Department of Obstetrics and Gynecology, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India
² Department of Radiodiagnosis, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India

Date of Submission	07-Nov-2017
Date of Acceptance	24-Feb-2020
Date of Web Publication	15-Dec-2020

Correspondence Address:
Dr. Mohd Ilyas
Department of Radiodiagnosis, Sher-i-Kashmir Institute of Medical Sciences, Srinagar - 190 011, Jammu and Kashmir
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jmgims.jmgims_60_17

Abstract

A case report of conjoined twins (thoracopagus-conjoined neck, thorax, and upper abdomen) diagnosed by routine ultrasonography in a 26-year-old G₂ P₁ pregnant female at 19 weeks of gestation is discussed. The pregnancy was terminated at this gestation with explained prognosis to the patient and consent of the family.

Keywords: Siamese twins, thoracopagus, ultrasonography

How to cite this article:
Khan I, Ilyas M, Shah SA, Saldanha CL. Siamese twins: Thoracopagus – A rare congenital anomaly. J Mahatma Gandhi Inst Med Sci 2020;25:116-8

How to cite this URL:
Khan I, Ilyas M, Shah SA, Saldanha CL. Siamese twins: Thoracopagus – A rare congenital anomaly. J Mahatma Gandhi Inst Med Sci [serial online] 2020 [cited 2023 Jun 4];25:116-8. Available from: https://www.jmgims.co.in/text.asp?2020/25/2/116/303423

Introduction

Conjoined twins represent one of the rarest forms of twin gestation. They occur in roughly 1 in 200 identical twin pregnancies. The incidence ranges from 1 in 50,000 to 1 in 100,000 live births.^[1] If the twinning is initiated after the embryonic disc and amniotic sac have formed and if the division of the embryonic disc is complete, conjoined twins result.^[2]

Case Report

A 26-year-old G₂ P₁ pregnant female with last childbirth as a full-term normal vaginal delivery female baby, with 5 month amenorrhea was referred to the radiology department for routine ultrasonography (USG) and to rule out any gross congenital anomalies. She had no previous ultrasound records. USG was performed using Logic-200 (GE-Healthcare). USG revealed two fetuses with two arms, two legs, and one head each [Figure 1]. The twins were joined at the neck, thorax, and upper abdomen with one umbilical cord and single fetal heart [Figure 2]. A single anterior wall upper segment placenta was seen. The biparietal diameters and femur lengths revealed the average gestational age of 19 weeks. The diagnosis of Siamese twin of the type thoracopagus was formulated and referred back to the Department of Gynecology and Obstetrics. After explaining the prognosis to the mother and family, the pregnancy was terminated by Cesarian section and findings confirmed postdelivery [Figure 2].

Figure 1: Cross-section of the ultrasound imaging showing the fused neck region and basal parts of the two fetal heads

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Figure 2: Immediate postdelivery photograph demonstrating fused neck, thorax, and upper abdomen of the conjoined twin, thus confirming the ultrasonography findings

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Discussion

The Conjoined twins are classified according to the most prominent site of conjunction: thorax (thoracopagus), abdomen (omphalopagus), sacrum (pyopagus), pelvis (ischiopagus), skull (cephalopagus), and back (rachipagus). Depending on the aspect of embryonic disc, the most common type is thoracopagus (19%).^[3]

The condition is more commonly found in females, with a ratio of 3:1 (female: male).^[4] Two theories have been proposed to explain this observation: the process of X-inactivation overlaps with the timing of monozygotic twinning and thus may directly contribute to the development of monozygotic twins, and the XX karyotype may confer a survival benefit.^[5]

Two contradicting theories exist to explain the origin of conjoined twins. The traditional theory is fission in which the fertilized egg splits partially, and conjoined twins represent delayed separation of the embryonic mass after day 12 of fertilization. The second theory is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find like-stem cells on the other twin and fuse the twins together.^[6],[7]

Early diagnosis of conjoined twins was previously reported, but not before the 10^th week of gestation.^[8] Once conjoined twins have been diagnosed, the characterization of the type and severity of the abnormality can be performed with ultrasound, computed tomography, or magnetic resonance imaging (MRI).^[9],[10] In our case, the prognosis was explained to the family, and since the family chose to terminate the pregnancy, no further diagnostic intervention was considered. Surgery to separate conjoined twins may range from relatively simple to extremely complex, depending on the point of attachment and the internal parts that are shared. Most cases of separation are extremely risky and life threatening. Ultrasound enables an early and accurate diagnosis of conjoined twins, which is vital for the obstetric management. MRI is reserved for better tissue characterization.^[11]

Conclusion

Conjoined twins are a rare type of congenital anomaly with a high degree of perinatal mortality. The thoracopagus is the most common type. Early diagnosis by ultrasound is beneficial for the patient which gives parents a chance for the termination of pregnancy and avoids late complications.

Learning points

Thoracopagus involves fusion of the thorax and upper abdomen, also called Type A conjoined twins
Accurate and early prenatal diagnosis is necessary for the proper management of the patient and to prevent the complications to the mother if a delay in diagnosis occurs
The ultrasound is one of the easily available and accurate methods for the diagnosis prenatally after 10 weeks of gestation as it helps in the diagnosis as well as characterization and to assess the severity of the malformation, although MRI remains the investigation of choice
Although Cesarian section is indicated in cases detected after 24 weeks, if a complicated case is there or if the patient requests, it should be performed for the convenience of the patient
Since the separation postdelivery is very risky and extremely life threatening to the patient, it is better to terminate the pregnancy once diagnosed
The later the diagnosis is made, the more are the chances of complications to the mother.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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