Diprosopus (Craniofacial Duplication) – A Congenital Defect
A craniofacial duplication is a rare form of congenital disorder which is commonly known as Diprosopus – wherein conjoined twins with duplicated faces are found.
Conjoined twins are born connected physically and are mostly of the same sex sharing a common placenta. Generally, single and a normal body trunk can be observed but the facial structures are duplicated with abnormalities such as the duplicated nose, eyes which are spaced far away from each other. However, in extreme cases, mostly the entire face has been duplicated that’s why the condition is called Diprosopus (Greek meaning ‘two-faced’). This suggests that the ovum has undergone an abnormal division.
Fetuses with diprosopus sometimes may also suffer through heart distortion, weakened neural tube and also anencephaly (lacking some portion of the brain). Interestingly, it has been observed that only 0.4% of conjoined twins suffer from this disorder.
What causes this disorder?
According to the researchers, the cause of this disease might be due to cranial divergence of the notochord that occurred during neurulation. This divergence leads to the formation of two vertebral axes and neural plates side by side, with neural crest derivatives.
Another possibility for this abnormality is due to the overexpression of the protein ‘Sonic Hedgehog’ (SHH- located on chromosome number 7) which acts as a chemical signal during embryonic development. Its monomer is encoded by the gene- shh which is then translated to a protein product of 462 amino acids. This protein plays a key role in the development of the frontal part of the brain, spinal cord, heart and many other parts of the body. It helps in cell growth & specialization and also acts as a morphogen.
Since it has a role in the cell division cycle, sometimes it may also lead to the formation of cancer. During the research, scientists exposed the embryos to excess SHH protein levels. As a result, chicks were born having two beaks and two eyes spacing apart from each other. In another case, less concentration of SHH protein showed the formation of fused eyes in the test animal.
Does early diagnosis of conjoined twins possible?
There are no such signs and symptoms which will indicate conjoined twins in pregnancy. In normal twins pregnancy, the uterus will grow faster than in case of a single fetus and also there might be more nausea, fatigue, and vomiting like conditions.
Conjoined twins can be identified by using ultrasound in the first three months that is the prenatal diagnosis. In the halfway of pregnancy, we can determine the extent of the twins connected and which organs they share by using ‘Echocardiograms’. If in early pregnancy it has been found that the fetus is suffering from such abnormality then abortion is sometimes considered as an option.
Associated complications in the condition
Most of the conjoined babies are born prematurely that’s why pregnancy with conjoined twins is complex and may lead to the chances of serious complications. Because of their anatomy cesarean section is considered to be important. In some cases, severe health issues can occur. The extent of complications depends upon which part or organ they are sharing.
Diprosopus is a rare form of craniofacial malformation observed in newborn babies where there is a partial or complete duplication of the face that can be observed. Though diprosopus is a rare disorder it has a sad effect when it appears. If the complication level is minor then it can be helped by surgery, but the complete cure for this is yet not discovered. Till date, there are approximately 35 cases that have been reported.
During studies, it has been found that the condition is predominant in females over males (2:1). In severe cases, most of the abnormalities are found in the central nervous system, respiratory system, and cardiovascular system. Though the cause of this deformity has been a matter of debate the most accepted theory is about the embryological disturbance that has been occurred during the 2nd week of pregnancy.
SHH protein can be one of the reasons for this anomaly since it has a major role in growth and development. Most of the babies are stillbirths and their survival rate is also very poor due to lots of anomalies. In some rare cases, surgery could be helpful if the connected parts are separable but the complete cure cannot be guaranteed. There are various cases wherein the separation was found to be successful with minimum loss of organs or damage to tissues. However, studies are still going on to improve the understanding of the condition and come up with a solution to minimize its occurrence.