Abdominal swelling lead to the diagnosis of a rare condition

General
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Recent Instagram post about 18 year old Narendra Kumar has caught my attention. While reading about more about this rare condition, I came across a published case report of a 2 and half year old girl who was presented with painless abdominal swelling in right hypochondrium.

Imaging revealed retroperitoneal mass containing structures resembling a vertebral column, pelvic and limb bones. Initially as fetiform teratoma was suspected, but following surgical removal and histopathological examination confirmed the diagnosis of fetus in fetu.

fetus in fetu
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SO, WHAT IS FETUS IN FETU ?

Fetus in Fetu is a rare development anomaly in which an abnormal mass develops within the body of host. In some cases mass may contain some partially developed structures like a vertebral column or limb buds which are not fully developed or functional.

How can Fetus in Fetu occur ?

1. Parasitic twin theory :

This theory suggests that Fetus in fetu results from aberrant twinning, an abnormal development of identical twins.

This may occur due to :

  • Incomplete splitting of a single embryo during early development, or
  • Early fusion of two separate embryos.
  • As a result one twin becomes enclosed within the body of the other twin.

2. Highly differentiated teratoma theory :

  • Proposes that Fetus in fetu is a highly organized and rare form of teratoma.
  • According to this theory, the mass develops as an unusually differentiated tumor rather than a parasitic twin.

Signs and symptoms :

  • Abdominal distension
  • Vomiting
  • Jaundice
  • Urine retention
  • Respiratory problems
  • Developmental issues

Diagnostic tests :

  1. Prenatal ultrasound – may identify well-defined mass with solid bony structure inside a newborn baby
  2. Computed Tomograph (CT) – Reveals the detail anatomy, the presence of vertebral columns and vascular formations.
  3. MRI – Particularly used in identifying Fetus in fetu masses deep inside the body.
  4. X- rays - may demonstrate calcified bones within the mass.
  5. Elevated Serum Alpha-fetoprotein (AFP) may be elevated in some cases and prompt for further investigations

Management :

  • Complete surgical removal of the mass.
  • Long-term follow up : Imaging and marker tracing (AFP)

Have you heard of “Fetus in fetu” before ? What are your thoughts on this rare condition?

More information about case report : Case report on fetus in fetu.

MBH/PS

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A fascinating and exceptionally rare developmental anomaly. What makes fetus in fetu particularly interesting is how it blurs the distinction between a highly organized teratoma and an aberrant twinning event. The presence of an axial skeleton, especially a vertebral column, is often a key feature supporting the parasitic twin theory. Cases like this highlight the importance of imaging and histopathology in diagnosing rare congenital conditions that can initially present with relatively nonspecific symptoms such as abdominal swelling.

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Never heard about this before but it is a fascinating case .Informative article. Imaging thus remains highly crucial tool in detection of many conditions.

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Insightful post! Never heard about this before. Would like to know more about the marker tracing which you have mentioned as AFP.

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In normal pregnancy condition serum alpha-fetoprotein(AFP) act as a standard fetal marker. High AFP levels may indicate abnormal neural tube defects, multiple pregnancies. Low AFP levels may indicate high risk of chromosomal abnormalities.

In case of fetus in fetu, since it contains highly active fetal tissue, it can cause severely elevated serum AFP levels in the host child. AFP testing can also help in differentiating malignant teratomas from Fetus in fetu, ass true teratomas do not produce highly elevated AFP.

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One of the rarest developmental conditions encountered in medicine. A great reminder of how intricate human embryogenesis can be

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That’s true.

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Had never heard of this condition! Knowing about such rare cases makes us wonder there is so much more to medical science. And this article was well put with proper references to sources.