Fetus in Fetu Presenting as a Second Head: A Rare Case Report with Pathologic Correlation

Area of Science:

• Medical Genetics
• Congenital Anomalies
• Perinatology

Background:

• Fetus in fetu (FIF) is a rare congenital anomaly involving a parasitic twin within a host, typically in the retroperitoneum.
• Oral FIF presentation is exceptionally rare, posing diagnostic challenges, especially differentiating it from teratomas like epignathus.
• Accurate diagnosis is critical for patient prognosis and effective management strategies.

Purpose of the Study:

• To report a unique case of oral fetus in fetu.
• To highlight the diagnostic challenges and clinical implications of this rare condition.
• To emphasize the importance of awareness for perinatal planning.

Main Methods:

• Case report of an 18-year-old patient presenting at 26 weeks gestation.
• Diagnostic imaging including ultrasound to assess fetal anomalies.
• Postmortem examination and histopathological analysis for definitive diagnosis.

Main Results:

• Ultrasound revealed an oropharyngeal mass, polyhydramnios, omphalocele, diaphragmatic hernia, and cardiac anomalies.
• Postmortem examination identified a fetiform mass resembling a head with cranial bones, facial features, and cerebral tissue.
• Histopathology confirmed fetus in fetu despite the absence of a vertebral axis.

Conclusions:

• This case represents a rare oral FIF predominantly composed of a second head, associated with significant host anomalies.
• Increased awareness of oral FIF is crucial for accurate diagnosis and informed perinatal planning, particularly concerning potential airway compromise.
• The distinct presentation underscores the variability of FIF and the importance of comprehensive evaluation.