What Is Diprosopus?
Diprosopus, or “two-faced syndrome,” is a very uncommon and life-threatening congenital condition that is characterized by partial or overall duplication of the craniofacial (cranium and face) skeleton or structures. The term “Diprosopus” is derived from the Greek terminology “di” which means two, and “Prosopon,” which means face. It is one of the developmental disorders that occurs during the embryonic development of the face. There are very rare cases of diprosopus that have been documented to date.
What Is the Incidence of Diprosopus?
Diprosopus is a very rare congenital anomaly with an incidence of around one in 15 million cases out of which the thoracopagus (joining at or around the sternal wall) is the most common form of conjoined twins. Craniofacial duplication is more common in females than males (2:1).
What Are the Possible Causes of Diprosopus?
The most possible accepted mechanisms of diprosopus are:
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During Neurulation: During the neurulation, bifurcation of the notochord may occur, resulting in duplication of the craniofacial skeleton. This bifurcation results in the formation of two vertebral axis and neural plates to develop closer to each other.
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Genetic Factor: Overexpression of the gene encoding protein sonic hedgehog is another possible cause of craniofacial duplication.
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Embryological Disturbances: It is one of the most accepted theories of craniofacial duplication. According to this theory, diprosopus or craniofacial duplication are monozygotic twins that occur due to embryological disturbance in egg separation during second week of pregnancy.
What Are the Different Systemic Disorders Associated With Diprosopus?
Various systemic disorders associated with diprosopus are:
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Central Nervous System (CNS): Associated disease is anencephaly. It is characterized by partial or total duplication of cerebral hemispheres and cervical spine. Other clinical presentations are arachnoid cyst (brain cyst), spina bifida (split spine), and hypoplasia of the temporal bone (lateral part of skull bone).
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Cardiovascular System (CVS): Associated with ventricular septal defect (abnormal communication between lower chambers of the heart) and hypoplastic aorta (inborn heart defects that are characterized by too narrow aortic arch).
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Renal System: Smaller urinary bladder and ureter, dysplastic kidneys are the associated symptoms of diprosopus.
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Gastrointestinal System: Associated gastrointestinal symptoms are diaphragmatic hernia (perforated diaphragm) and imperforate anus.
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Head and Neck Abnormalities: Cleft lip (common inborn defect associated with split lip) and cleft palate (common inborn defect associated with split in palate).
What Are the Different Classifications of Craniofacial Duplication?
Different classifications of craniofacial duplication are:
Barr's classification (1982) of duplication of craniofacial structure is divided into three forms:
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Form I: Eyes and nose duplication with or without duplication of the upper jaw.
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Form II: Duplication of the nose with or without duplication of the upper jaw.
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Form III: Duplication of the upper jaws with or without lower jaw duplication.
Gorlin's (1990) classification of oral structures duplication involves:
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One mouth with duplication of the upper jaw.
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A supernumerary mouth placed laterally with an underdeveloped lower jaw.
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A single mouth with duplication of lower jaw segments.
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Craniofacial duplication (diprosopus) with or without anencephaly.
What Are the Risk Factors for Diprosopus?
Various risk factors associated with diprosopus are:
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Family history.
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Advanced maternal age.
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Genetic mutation.
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Environmental factors like teratogenic drugs.
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History of polyhydramnios (abnormally high amount of amniotic fluid in the amniotic sac).
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How Can Diprosopus Be Diagnosed?
Diprosopus can be diagnosed by the following methods:
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Clinical Examination: A thorough clinical examination of the facial structures for any abnormalities should be performed by the doctor to diagnose the diprosopus.
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Radiographic Examination: A four-dimensional ultrasound scan helps to diagnose all craniofacial malformations effectively. Prenatal ultrasound, magnetic resonance imaging, and computed tomography scan help to rule the diprosopus in the early stages.
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Genetic Screening: Genetic screening helps to rule out any genetic abnormalities or defects in gene-encoding proteins (sonic hedgehog gene). Any chromosomal abnormalities can be detected if present.
What Are the Management Protocols for Diprosopus?
Management of diprosopus requires a multidisciplinary team approach involving healthcare professionals in different specialties like neonatology, geneticists, pediatrician, and plastic surgeons. Treatment protocols involve step-by-step approaches such as:
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Restoring the Basic Functions: Initial step involves addressing the underlying symptoms along with ensuring proper feeding and respiration of the fetus. Healthcare professionals should make sure that sufficient oxygen is reaching the patient's respiratory system. Doctors should make sure the fetus is getting adequate nutrition.
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Surgical Management: Surgical corrections might be needed to restore functional defects. The decision for surgery depends on the extent of the duplication defect, and surgical techniques are different in different patients varying on the severity of the craniofacial duplication defects. However, the long-term survival rate of the fetus after the surgery is very low.
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Cosmetic Corrections: Cosmetic defects corrections are achieved at a later stage after correcting the functional abnormalities. Complete cosmetic correction and restoration of the normal facial anatomy are very difficult to achieve in severe craniofacial duplication cases.
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Genetic Counseling: Genetic counseling of the patient's parents needs to be done to explain to them the risk of surgeries and prognostic health outcomes of the fetus after birth.
What Is the Differential Diagnosis of Diprosopus?
Differential diagnoses of diprosopus or craniofacial duplication are:
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Teratomas: It is a rare germ cell tumor consisting of various tissues like skin, bone, muscle, or hair tissues.
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Acardiac Fetus: It is also known as an acardiac twin. It is an inborn defect characterized by the absence of a heart or the presence of an underdeveloped heart.
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Fetus in Fetu: It is a rare inborn anomaly characterized by a structurally malformed or parasitic fetus present in the body of its twins. The anomaly was first described by Meckel in the early nineteenth century.
Conclusion
Diprosopus is a very uncommon phenomenon characterized by duplication of craniofacial structures. There are barely many cases reported in the literature. Prenatal and genetic screening plays a vital role in the early diagnosis of craniofacial anomalies in the fetus. However overall survival rate of the fetus after birth is very poor due to multiple craniofacial abnormalities. Further research is yet needed to understand the exact cause of diprosopus and newer diagnostic approaches to early intervention of the craniofacial duplication anomaly.
