Sirenomelia type VI (sympus apus) in one of dizygotic twins at Chiang Mai University Hospital

Abstract

Those born with sirenomelia, a rare congenital anomaly, have features resembling a mermaid. Characteristics of sirenomelia are a single lower limb, sacral and pelvic bone defects, and anorectal and urogenital malformations. There is an increased incidence of sirenomelia in males and twins. This case was a preterm male, dizygotic twin and product of in vitro fertilisation. The baby was born by caesarean section due to breech presentation. He was found to have a fused lower extremity and absent external genitalia and anus. The baby passed away shortly after birth due to severe respiratory failure. Radiographic findings showed small lung volume and pneumothoraces. There were multiple segmental fusions of the vertebrae. Single femur and single tibia were presented in a fused lower limb. Autopsy demonstrated large intestinal atresia, intra-abdominal testes, absence of kidney, ureter and bladder, single umbilical artery, agenesis of blood vessels at lower extremity and agenesis of sacrum and coccyx.

Figure 1

Morphological appearance of the patient showed a dysmorphic face, a single fused lower limb and absence of external genitalia and anus.

Figure 2

Bifid right thumb.

Figure 3

Radiograph of the body demonstrating bilateral pneumothoraces, fusion of the T12-L1, L2-3 and L4-5 vertebrae, absent left hip, rudimentary right ileum and single right lower limb with hypoplastic femur and tibia.