A Parasitic Twin Diagnosed Prenatally As a Sacrococcygeal Teratoma: A Case Report

Abstract

Parasitic twinning is a rare entity. It is an asymmetric conjoined twinning in which a poorly formed twin, known as the parasite, is attached to a fully developed co-twin, known as the autosite. The parasite depends on the autosite for blood supply. It is diagnosed prenatally with ultrasound, and treatment involves resection of the parasite postnatally. We describe a case that was prenatally diagnosed on 2D ultrasound as a sacrococcygeal teratoma at 25 weeks.No other anomaly was detected. Caesarean delivery was conducted at 34 weeks on account of failure to progress following spontaneous preterm labour.At delivery, we found that the sacrococcygeal mass was a parasitic twin with a poorly formed body, lower limb, and hair. These fetal components were not demonstrated on the prenatal 2D ultrasound. Postnatal assessment revealed no other abnormality. The mass was successfully resected on day 3 of life. The resection was done early on account of ulceration of the mass/ parasite. The histopathological assessment revealed more fetal parts, including brain tissue and lungs. Prenatal diagnosis is essential as it identifies associated anomalies and helps with prognostication and planning of obstetric and surgical management by a multidisciplinary team.