Diprosopus

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Diprosopus (Greek διπρόσωπος, "two-faced", from δι-, di-, "two" and πρόσωπο[ν], prósopo[n] [neuter], "face", "person"; with Latin ending), also known as craniofacial duplication (cranio- from Greek κρανίο, "skull", the other parts Latin), is an extremely rare congenital disorder whereby part or all of the face is duplicated on the head.[1][2]

Contents

[edit] Development

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 a protein called sonic hedgehog homolog (SHH). (The unlikely-sounding name of this protein was inspired by the Sonic the Hedgehog videogame character[3] and is part of an idiosyncratic naming tradition in molecular biology research that some have criticized as frivolous.[4][5])

The SHH protein and its corresponding gene have been found to play an important role in signaling craniofacial patterning during embryonic development. Among other things, the SHH protein governs the width of facial features. In excess it leads to widening of facial features and to duplication of facial structures.[6] The greater the widening, the more of the 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. Insufficient amounts of that protein lead to opposite conditions such as cyclopia where facial features are insufficiently developed.[7]

Healthy brain development is also dependent on the signaling function of the SHH protein.[8] During embryonic development, the SHH protein directs embryonic cells to organize in specific areas that later become specialized neural tissues, thus controlling the size and shape of brain structures.

[edit] Occurrences

Diprosopus often occurs in combination with other congenital disorders, particularly anencephaly, neural tube defect and cardiac malformations.[9] When present, the brain may show abnormalities ranging from partial to complete duplication of brain structures, and/or underdevelopment of brain tissues.[10][11]

Few two-faced animals have survived due to associated internal organ abnormalities and brain abnormalities. One of the most famous was Ditto the pig.[12] Ditto was raised to adulthood, but died of pneumonia caused by food inhalation when breathing through one muzzle while eating with the other. In July 2006, a 6-year-old two-faced cat called "Frank and Louie" from Millbury, USA received publicity. In this latter case, only one esophagus (and possibly only one trachea) was functional and this aided survival.

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.[13][14] 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 ending in 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.

In 2008, a baby girl born in India, Lali Singh, became the most recently known person to have the condition diprosopus.[2][15] Born 11 March 2008, she is one of the very few infants with diprosopus to survive well past birth. She may be the only known living individual with complete facial duplication. Her facial features include two pairs of eyes, two noses, and two mouths (but only one pair of ears). Lali Singh, daughter of Sushma and Vinod Singh, lives in the Indian village of Saini Sunpura. There, she is seen as the reincarnation of the goddess Durga, who has three eyes.

As of April 2008, Sushma and Vinod Singh have declined an offer from local doctors to evaluate their daughter through CT or MRI scanning. Without diagnostic imaging, it is not possible to know the full extent to which the child's condition may affect her brain and other vital structures in her head and neck. Thus, any estimation of her ability to survive or even thrive can only be speculative, though Lali's family describes her as functioning normally. It is also unknown whether medical experts, if consulted, would have feasible solutions to offer with respect to corrective surgery.

[edit] See also

[edit] References

  1. ^ Definition of diprosopus at MedicineNet. Accessed 8 January 2006.
  2. ^ a b 'Miracle baby' is feted in India at BBC News. Accessed 10 April 2008.
  3. ^ Donahue JK. Gene therapy, angiogenesis, Sonic Hedgehog: Sonic The Hedgehog to the rescue? Gene Therapy 2006;13:998–999. doi:10.1038/sj.gt.3302748; published online 2 March 2006.
  4. ^ Maclean K. Humour of gene names lost in translation to patients. Nature 2006;439(7074):266.
  5. ^ Bye-Bye, Sonic Hedgehog. Discover 1 February 2007.
  6. ^ Hu D and Helms JA. The role of Sonic Hedgehog in normal and abnormal craniofacial morphogenesis. Development 1999;126:4873-84. Accessed 9 April 2008.
  7. ^ Young DL, Schneider RA, Hu D, Helms JA. Genetic and teratogenic approaches to craniofacial development. Crit Rev Oral Biol Med. 2000;11(3):304-17. Accessed 10 April 2008.
  8. ^ Sonic Hedgehog shapes the brain. ScienceDaily 13 March 2001.
  9. ^ al Muti Zaitoun A, Chang J, Booker M. Diprosopus (partially duplicated head) associated with anencephaly: a case report. Pathol Res Pract. 1999;195(1):45-50. Accessed at PubMed 8 January 2006.
  10. ^ Koseoglu K, Gok C, Dayanir Y, Karaman C. CT and MR imaging findings of a rare craniofacial malformation: diprosopus. Am J Roentgenol 2003; 180:863-4.] Accessed 8 January 2006.
  11. ^ Angtuaco TL, Angtuaco EJ, Quirk JG. US case of the day. Radiographics 1999;19:260-63. Accessed 20 April 2008.
  12. ^ Leroi Armand-Marie (2005). Mutants: On the Form, Varieties and Errors of the Human Body. New York: HarperPerennial. (ISBN 0-00-653164-4)
  13. ^ Hähnel S, Schramm P, Hassfeld S et al. Craniofacial duplication (diprosopus): CT, MR imaging, and MR angiography findings - case report. Radiology 2003;226:210-13. Accessed 20 April 2008.
  14. ^ Wu J, Staffenberg DA, Mulliken JB, Shanske AL. Diprosopus: A unique case and review of the literature. Teratology 2002; 66:282–87. Accessed 20 April 2008.
  15. ^ Two-Faced Baby Triggers Shock and Awe ABC report. Accessed 21 April 2008.

[edit] External links