A parasitic twin, also called fetus-in-fetu, is a rare congenital anomaly in which a twin fetus engulfs or absorbs the other twin fetus, which is physically underdeveloped. The developed fetus is known as “Autosite,” while the incomplete twin, which often lacks vital organs like the brain or heart, is called “Parasite.”
This condition falls into a conjoined twin, but typically, a conjoined twin where both twins are capable of independent life; here, only one is viable.
How does it occur?
Normally, a fertilized egg splits into two separate embryos; here, the division is incomplete or disrupted.
- Incomplete separation of the embryo
- Selective degeneration, where one twin stops developing and becomes dependent.
As a result, the parasitic twin remains attached and relies entirely on the host twin for blood supply and survival.
Types Of Parasitic Twins:
Parasitic twins can present in different forms:
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External Parasitic Twin: Visible extra limbs or body parts attached to the host
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Internal Parasitic Twin (Fetus in fetu): The undeveloped twin is found inside the body of the host, often detected later in life.
Parasitic twinning stands as a powerful reminder of how delicate and complex human development truly is.
Read more : Parasitic Twins: Causes, Symptoms, and Treatment