Mermaid Syndrome: Navigating the Challenges of a Rare Congenital Disorder

Abstract

Sirenomelia, or mermaid syndrome, is a rare congenital disorder characterized by the fusion of lower limbs and often associated with multisystem organ dysfunction, resulting in poor survival beyond the neonatal period. We report a case of sirenomelia in a full-term infant born to a 28-year-old primigravida with no significant medical history, gestational diabetes, or teratogenic exposure. The antenatal period was complicated by oligohydramnios, though routine ultrasounds failed to detect the condition. The diagnosis of sirenomelia was only made after delivery by cesarean section, with a compatible-with-life appearance, pulse, grimace, activity, and respiration (APGAR) score. The infant was referred to the pediatric surgical department due to abdominal distension and fused lower limbs, with plans to manage these conditions if the infant survived long-term. During the three-day hospital stay, vomiting was noted, and a babygram confirmed Stocker and Heifetz type IV sirenomelia and distended large bowel. An exploratory laparotomy revealed gross gastrointestinal and genitourinary abnormalities. A sigmoid colostomy was performed to relieve obstruction. Unfortunately, the infant expired shortly after surgery. This case highlights the challenges of prenatal diagnosis and the limited understanding of surgical management in sirenomelia, particularly given the rarity of survival beyond the neonatal period.

Keywords: congenital anomaly; mermaid syndrome; neonatal surgery; oligohydramnios; sirenomelia.

Figure 1. Infant with normal chest, distended abdomen, and fusion of lower limbs from the perineum to the ankle, with feet facing posteriorly (A). Facial features consistent with Potter facies, including a slit-like mouth (black arrow) and low-set ears (blue arrow) (B). Posterior view displaying a flat perineum, a lumbosacral dermal pit (black arrow), and a nonspecified opening with mucosa protruding (blue arrow) (C). Feet fused medially (D). Babygram showing partially fused femurs (orange arrow), two tibias, and an abnormally positioned medial fibula (blue arrow); yellow arrow shows distended large bowel (E)

Figure 2. Classification of sirenomelia by the presence or absence of bones within the lower limb. (I) All bones of the thigh and lower leg present. (II) Fused fibula. (III) Fibula absent. (IV) Partially fused femur, fused fibula. (V) Partially fused femur. (VI) Fused femur, fused tibia. (VII) Fused femur, tibia absent

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