Diprosopus

Diprosopus (Greek διπρόσωπος, 'two-faced', from δι-, di-, 'two' and πρόσωπον, prósopon , 'face', 'person'; with Latin ending), also known as craniofacial duplication (cranio- from Greek κρανίον, 'skull', the other parts Latin), is an extremely rare congenital disorder whereby parts (accessories) or all of the face are duplicated on the head. Diprosopus (Greek διπρόσωπος, 'two-faced', from δι-, di-, 'two' and πρόσωπον, prósopon , 'face', 'person'; with Latin ending), also known as craniofacial duplication (cranio- from Greek κρανίον, 'skull', the other parts Latin), is an extremely rare congenital disorder whereby parts (accessories) or all of the face are duplicated on the head. Although classically considered conjoined twinning (which it resembles), this anomaly is not normally due to the fusion or incomplete separation of two embryos. It is the result of abnormal activity by the protein SHH (sonic hedgehog). (The name of this protein was inspired by the Sonic the Hedgehog video game character and is part of an idiosyncratic naming tradition in molecular biology research.) SHH and its corresponding gene have been found to play an important role in signaling craniofacial patterning during embryonic development. Among other things, SHH governs the width of facial features. In excess it leads to widening of facial features and to duplication of facial structures. The greater the widening, the more structures are duplicated, often in a mirror image form. This has been demonstrated in the laboratory by introducing pellets of the SHH protein into chicken embryos, resulting in chickens with duplicate beaks. Inadequate amounts of that protein lead to opposite conditions such as cyclopia where facial features are insufficiently developed. Healthy brain development is also dependent on the signaling function of SHH. During embryonic development, SHH directs embryonic cells to organize in specific areas that later become specialized neural tissues, thus controlling the size and shape of brain structures. Diprosopus often occurs in combination with other congenital disorders, particularly anencephaly, neural tube defect and cardiac malformations. When present, the brain may show abnormalities ranging from partial to complete duplication of brain structures, and/or underdevelopment of brain tissues. Most human infants with diprosopus are stillborn. Known instances of humans with diprosopus surviving for longer than minutes to hours past birth are very rare; only a few are recorded. In 2002 and 2003, two living male infants with partial diprosopus were described in the medical literature in separate case reports. One infant was born with duplication of the nose and the cerebral frontal lobes, two widely spaced eyes, a small, underdeveloped central eye socket, and a large, asymmetric mouth. The other infant was born with duplication of the upper and lower jaw, two tongues arising from the same base, cleft palate, a slightly divided tip of the nose, and two widely spaced eyes, as well as absence of the corpus callosum, duplication of the pituitary gland and stalk, and abnormalities in the midbrain. Because they were born with a milder, partial form of diprosopus, both infants were considered candidates for surgical correction of their abnormal facial features. Lali Singh (10 March - 10 May 2008) was born to Sushma and Vinod Singh in Saini, Sunpura Sohanpur village, near Delhi; the birth was delayed by dystocia caused by her large head, and her birth in a hospital was facilitated by her mother's receiving an episiotomy. She was one of the very few infants with diprosopus to survive well past birth. She might have been the only known living individual with complete facial duplication. Her facial features included two pairs of eyes, two noses, and two mouths (but only one pair of ears). She was seen as the reincarnation of the goddess Durga, who is sometimes depicted with many limbs and eyes. Sushma and Vinod Singh declined an offer from local doctors to evaluate their daughter through CT or MRI scanning. Without diagnostic imaging, it was not possible to know the full extent to which the child's condition might have affected her brain and other vital structures in her head and neck. Thus, any estimation of her ability to thrive or even survive could be only speculative, though Lali's family described her as functioning normally. It is also unknown whether neurosurgeons or craniofacial surgeons, if consulted, would have had feasible solutions to offer with respect to corrective surgery. A local doctor told reporters that the baby should be considered a healthy child who currently was living a normal life, a previously unknown occurrence among sufferers of the disorder. Lali's two middle eyes suffered from corneal opacity due to abnormal anatomy of the facial muscles, which prevented her from properly closing those eyes. (Initially, this was wrongly blamed on camera flashes.)