Parasitic Twin Detected in a 47-Year-Old Woman With a Lifelong Abdominal Mass

A rare case of a parasitic twin, medically termed epigastric heteropagus, was identified in a 47-year-old woman who had carried the mass since birth. The patient, a mother of four, presented to clinicians with a progressively enlarging abdominal swelling, ultimately revealed to be a partially formed parasitic twin attached to her upper abdomen.

Parasitic twinning is an exceptionally uncommon congenital anomaly, estimated to occur in fewer than 1 in 1 million births. Unlike symmetrical conjoined twins, parasitic twins involve a severely underdeveloped “dependent” twin attached to a fully developed “autosite.” ¹

What Is a Parasitic Twin?

Parasitic twins, also called heteropagus twins, form due to abnormal embryonic division. Two primary theories explain their development:

• Fission Theory: incomplete splitting of a developing embryo.

• Fusion Theory: two monozygotic embryos fuse during early development.

A third hypothesis suggests that in-utero vascular compromise causes one twin to stop developing while remaining physically attached to the other.

Parasitic twins may appear at one of eight anatomical attachment sites, including the thorax, abdomen, pelvis, spine, or cranial region.

Epigastric heteropagus, the type observed in this patient, is among the rarest forms.

Case Overview: A Lifelong Abdominal Mass

The 47-year-old woman reported that the mass had been present since birth and had gradually increased in size. Despite carrying four pregnancies to term, each delivered vaginally at home, she had never undergone medical evaluation for the deformity.

Clinical Findings of the patient with the parasitic twin

• Pale appearance; hemoglobin level at 9 g/dL, suggesting anemia

• Pedunculated abdominal mass measuring approximately 24 × 16 × 12 cm

• Primitive facial features observed on the mass:

  • One ear

  • A rudimentary nose

  • Limb buds

• Varied tissue consistency and uneven surface

Imaging and Diagnostic Evaluation

Contrast-enhanced CT and CT angiography revealed:

• A soft-tissue mass extending across the anterior thorax and abdomen

• Clearly identifiable primitive organs within the parasitic twin, including:

  • Liver

  • Single kidney

  • Vertebrae

  • Unilateral chest cage

• A pedicle connecting the parasite to the host

• Vascular supply originating from the woman’s right superior epigastric artery

These findings differentiated the mass from teratomas and supported the diagnosis of epigastric heteropagus twin.

Surgical Management and Removal of the Parasitic Twin

A complete excision of the parasitic twin was performed. Surgeons removed the mass en toto along with a portion of preperitoneal fat. No organ sharing existed, simplifying the surgical approach.

The abdominal defect, measuring nearly 9 × 5.5 cm, was closed primarily without the need for grafts or tissue expanders.

The patient recovered well and was discharged on postoperative day 12.

Discussion: Significance of This Case

This case is notable for several reasons:

1. Oldest Known Age at Surgical Removal

Most parasitic twins are discovered at birth. Delayed diagnosis into adulthood is rare; presentation at 47 years may be one of the oldest documented.

2. Complex Anatomy

The presence of limb buds, vertebrae, primitive facial structures, and partially developed organs indicates advanced development of the parasitic twin compared with typical heteropagus presentations.

3. Sociocultural Factors

The authors suggest delayed care may relate to stigma, limited access to healthcare, and cultural barriers in rural regions.

4. Importance of Pre-operative Imaging

Detailed vascular mapping via CT angiography is essential to prevent hemodynamic compromise during surgical removal.

Parasitic Twins vs. Fetus-in-Fetu

While sometimes confused, the two conditions differ:

ConditionKey FeaturesParasitic Twin (Heteropagus)Externally attached undeveloped twin; shares blood supply via pedicleFetus-in-Fetu (FIF)Internal mass containing vertebrae and organ structures; thought to result from inclusion of one embryo within another

FIF occurs in approximately 1 in 500,000 births, whereas parasitic heteropagus twins are even rarer.

Epigastric heteropagus is an extremely rare form of parasitic twinning. Early diagnosis and imaging are essential for evaluating shared anatomy, vascular supply, and surgical risks. Despite the size and complexity of the mass, the patient made a successful recovery following complete excision.

Reference

1. Singhal, J., S. Gupta, V. K. Agarwal, et al. “Unique Case of Epigastric Heteropagus Twins: A Surgical Challenge.” Cureus 17, no. 4 (April 17, 2025): e82421. https://doi.org/10.7759/cureus.82421.

(Rh/TL)