A parasitic twin, also known as an asymmetrical twin or unequal conjoined twin, occurs when a twinembryo begins developing in utero, but the pair does not fully separate, and one embryo maintains dominant development at the expense of the other. It results from the same processes that also produces vanishing twins and conjoined twins, and may represent a continuum between the two. In parasitic twins, one ceases development during gestation and is vestigial to a mostly fully formed, otherwise healthy individual twin. The undeveloped twin is termed as parasitic, because it is incompletely formed or wholly dependent on the body functions of the complete fetus.[1] The independent twin is called the autosite.
Parasitic twin
Illustration of a man with a parasitic twin, alongside illustrations of two configurations of conjoined twins
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TRAP syndrome. The acardiac twin, left, cannot pump its own blood. The pump twin, right, supplies blood to the parasitic twin.
TRAP sequenceedit
The twin reversed arterial perfusion, or T.R.A.P. sequence, results in an 'acardiac twin', a parasitic twin that fails to develop a head, arms and a heart. The parasitic twin, little more than a torso with or without legs, receives its blood supply from the host twin by means of an umbilical cord-like structure, much like a fetus in fetu, except the acardiac twin is outside the autosite's body. The blood received by the parasitic twin has already been used by the normal fetus, and as such is already de-oxygenated, leaving little developmental nutrients for the acardiac twin. Because it is pumping blood for both itself and its acardiac twin, this causes extreme stress on the normal fetus' heart. Many T.R.A.P. pregnancies result in heart failure for the healthy twin. This twinning condition usually occurs very early in pregnancy.[2] A rare variant of the acardiac fetus is the acardius acormus where the head is well developed but the heart and the rest of the body are rudimentary. While it is thought that the classical T.R.A.P./Acardius sequence is due to a retrograde flow from the umbilical arteries of the pump twin to the iliac arteries of the acardiac twin resulting in preferential caudal perfusion, acardius acormus is thought to be a result of an early embryopathy.[3]
Othersedit
Conjoined parasitic twins joined at the head are described as craniopagus or cephalopagus, and occipitalis if joined in the occipital region or parietalis if joined in the parietal region.
Craniopagus parasiticus is a general term for a parasitic head attached to the head of a more fully developed fetus or infant.[4]
Fetus in fetu sometimes is interpreted as a special case of parasitic twin, but may be a distinct entity.
^"the same year that peace was made with the Swiss by King Francis"
^"Parasitic Twins | The Embryo Project Encyclopedia". embryo.asu.edu. Retrieved 2022-02-18.
^"Acardiac Twin or TRAP Sequence". University of California, San Francisco. 2007-04-26. Archived from the original on 2012-07-08. Retrieved 2007-05-30.
^Abi Nader Khalil, Whitten Sara Melissa, Filippi Elisa, Scott Rose-Mary, Jauniaux Eric. Dichorionic triamniotic triplet pregnancy complicated by acardius acormus. Fetal Diagnosis and Therapy 2009;26(1):45-9.
^Aquino DB, Timmons C, Burns D, Lowichik A (1997). "Craniopagus parasiticus: a case illustrating its relationship to craniopagus conjoined twinning". Pediatric Pathology and Laboratory Medicine. 17 (6): 939–44. doi:10.1080/107710497174381. PMID 9353833.
Further readingedit
Lebel, Robert Roger; Carlos Mock; Jeannette Israel; William Senica (June 1994). . TheFetus.net. Archived from the original on 1 October 2019. Retrieved 18 February 2013.
May 20, 2024
parasitic, twin, parasitic, twin, also, known, asymmetrical, twin, unequal, conjoined, twin, occurs, when, twin, embryo, begins, developing, utero, pair, does, fully, separate, embryo, maintains, dominant, development, expense, other, results, from, same, proc. A parasitic twin also known as an asymmetrical twin or unequal conjoined twin occurs when a twin embryo begins developing in utero but the pair does not fully separate and one embryo maintains dominant development at the expense of the other It results from the same processes that also produces vanishing twins and conjoined twins and may represent a continuum between the two In parasitic twins one ceases development during gestation and is vestigial to a mostly fully formed otherwise healthy individual twin The undeveloped twin is termed as parasitic because it is incompletely formed or wholly dependent on the body functions of the complete fetus 1 The independent twin is called the autosite Parasitic twinIllustration of a man with a parasitic twin alongside illustrations of two configurations of conjoined twinsSpecialtyMaternal fetal medicine neonatology Contents 1 Variants 1 1 TRAP sequence 1 2 Others 2 Gallery 2 1 Human 2 2 Animals 3 See also 4 References 5 Further readingVariants editThis section is in list format but may read better as prose You can help by converting this section if appropriate Editing help is available December 2016 nbsp TRAP syndrome The acardiac twin left cannot pump its own blood The pump twin right supplies blood to the parasitic twin TRAP sequence edit The twin reversed arterial perfusion or T R A P sequence results in an acardiac twin a parasitic twin that fails to develop a head arms and a heart The parasitic twin little more than a torso with or without legs receives its blood supply from the host twin by means of an umbilical cord like structure much like a fetus in fetu except the acardiac twin is outside the autosite s body The blood received by the parasitic twin has already been used by the normal fetus and as such is already de oxygenated leaving little developmental nutrients for the acardiac twin Because it is pumping blood for both itself and its acardiac twin this causes extreme stress on the normal fetus heart Many T R A P pregnancies result in heart failure for the healthy twin This twinning condition usually occurs very early in pregnancy 2 A rare variant of the acardiac fetus is the acardius acormus where the head is well developed but the heart and the rest of the body are rudimentary While it is thought that the classical T R A P Acardius sequence is due to a retrograde flow from the umbilical arteries of the pump twin to the iliac arteries of the acardiac twin resulting in preferential caudal perfusion acardius acormus is thought to be a result of an early embryopathy 3 Others edit Conjoined parasitic twins joined at the head are described as craniopagus or cephalopagus and occipitalis if joined in the occipital region or parietalis if joined in the parietal region Craniopagus parasiticus is a general term for a parasitic head attached to the head of a more fully developed fetus or infant 4 Fetus in fetu sometimes is interpreted as a special case of parasitic twin but may be a distinct entity Gallery editHuman edit nbsp German man born 1516 a nbsp 40 year old man seen in Paris 1530 nbsp Lazarus and Joannes Baptista Colloredo born 1617 nbsp 30 year old Neapolitan man seen in 1742 nbsp Indian man 1787 nbsp Agan a Chinese man 1833 nbsp 9 year old Gustav Evrard of Paris 1839 nbsp Blanche Dumas of France born 1860 nbsp Louise L born 1869 nbsp Joao Baptista dos Santos and Louise L la femme de quatre jambes 1893 nbsp Laloo 1897 Animals edit nbsp Chicken with two extra lower limbs nbsp Pigeon with two extra lower limbs nbsp Cat with lower body duplication nbsp Sheep with two extra front limbsSee also editDipygus Frank Lentini Lakshmi Tatma Lazarus and Joannes Baptista Colloredo Rudy Santos Twin reversed arterial perfusion Vestigial twinReferences edit the same year that peace was made with the Swiss by King Francis Parasitic Twins The Embryo Project Encyclopedia embryo asu edu Retrieved 2022 02 18 Acardiac Twin or TRAP Sequence University of California San Francisco 2007 04 26 Archived from the original on 2012 07 08 Retrieved 2007 05 30 Abi Nader Khalil Whitten Sara Melissa Filippi Elisa Scott Rose Mary Jauniaux Eric Dichorionic triamniotic triplet pregnancy complicated by acardius acormus Fetal Diagnosis and Therapy 2009 26 1 45 9 Aquino DB Timmons C Burns D Lowichik A 1997 Craniopagus parasiticus a case illustrating its relationship to craniopagus conjoined twinning Pediatric Pathology and Laboratory Medicine 17 6 939 44 doi 10 1080 107710497174381 PMID 9353833 Further reading editLebel Robert Roger Carlos Mock Jeannette Israel William Senica June 1994 Twin reversed arterial perfusion syndrome acephalic presenting at full term TheFetus net Archived from the original on 1 October 2019 Retrieved 18 February 2013 Retrieved from https en wikipedia org w index php title Parasitic twin amp oldid 1223828443, wikipedia, wiki, book, books, library,
