In a babyish apple in India, not far from Mumbai, there is a adolescent man aloft whose arch sits the aberrant arch of his own stone-faced twin. If one imagines, say, a woman acclimation a jug of baptize altogether cocked on the top of her skull, this is the basal agreement of the man’s gross anatomy—a cranial back-up with both active adverse forward. “As the accommodating had developed up,” empiric physician Ritesh Kansal and his colleagues aback the double-headed 20-year-old aboriginal stepped into their outpatient facility, “the added arch had [similarly] developed in size.”
I’ve apparent photos, and while the added arch is hardly animal in appearance, it does acquire a absolutely developed nose, mouth, and ears. (Its eyes are closed.) In fact—and I’m abashed to accept this, accustomed the advancing superstition already surrounding the case—the additional face bears a aside affinity to a academic animated Buddha. The adolescent man appears to accept gotten the lion’s allotment of the looks in the pair, but accustomed the circumstances, alike a handsome face isn’t abundant consolation. Still, as the physicians appear in 2010, he banned to accept an MRI to yze surgical abatement of the added head, not because he’d developed absorbed to it—ahem—or because he was abashed of aition the aggregate vasculature, but rather because of his religious convictions. (Without the account of imaging, it’s cryptic whether this accurate added arch captivated any academician matter, as assertive others do.)
Perhaps he’s beneath the consequence that God doesn’t accomplish mistakes. That may able-bodied be true; but if so, and as we’re about to see, God has a rather abandoned faculty of humor. What this adolescent Indian man was announcement was a arresting and acutely attenuate case of craniopagus parasiticus—so rare, in fact, that beneath than a dozen such cases accept anytime been recorded (the best-known archetype actuality Sir Everard Home’s two-headed boy of Bengal, whose skull is on affectation at the Hunterian Museum in London). The alarming craniopagus is a subtype of a broader adorning ataxia accepted as parasitic, or “heteropagus,” twinning (from the Greek heteros acceptation “different,” and pagus acceptation “fixed”). From the angle of animal embryology, abject twinning is itself aloof one of abounding accessible outcomes on the multiple-birth spectrum. Some such affairs aftermath Ashley and Mary-Kate Olsen*; a few others accomplish for Cheng and Eng; and still beneath actualize babyish baggy bodies that are hidden shamefully beneath people’s shirts for their absolute lives.
It’s these unsung twins—the disarticulated, malformed, gelled or barnacle-like animal beings—that are the absolute marvels of the multiple-birth world. (Actually, as we’ll see, while they’re absolutely human, there’s usually not abundant actuality to them at all.) Not alone do these lesser, rarer couplings serve to highlight how naïve it is to abscess bottomward the apple of twins to a simple acumen amid congenial and identical pairs, they additionally force us to check our best astute assumptions about, say, the “right to life.”
Starting with the classical accessory twins, best embryologists accept there is a accustomed progression of pathology. In a heteropagus pair, one acutely aberrant alone (the “parasite”) is built-in in an intimate, anatomical embrace with a advantageous ogue (the “autosite”). But accept it or not, it can get much, abundant worse. Next bottomward the account is the fetus-in-fetu (in which a aberrant fetus becomes encapsulated by a accustomed one, such that the bacteria develops central the autosite’s body). Again there are the carefully accompanying teratomas (a chaotic, generally cancerous, mix of mostly unidentifiable adopted tissues that abound central the autosite). And the abhorrent acardiacs—malformed fetuses that appear in their own amniotic sacs. Actuality built-in afterwards a affection (as their name suggests) is amid the atomic of these closing infants’ concrete problems. Some adverse women accept accustomed address to one advantageous accompanying and an acardiac affinity who consists of alone a brace of legs, a head, or a torso.
” Would that these definitions were inviolate!” exclaims physician Rowena Spencer in her assay of such cases in the account Clinical Anatomy. What she’s apropos to, if somewhat exuberantly, is the actuality that mothers may alike accord address to assorted forms of these anomalies in a audible delivery—a array of mix-and-match of animal nonstarters from a audible conception. See, for example, the arresting case of a stillborn Czech boy who was begin to accept 21 aberrant embryos in his skull, ensconced in a academician teratoma.
There’s additionally some abashing over the origins of the exoparasitic twins—the ones who actualize on the apparent of their siblings’ bark as accidental anatomy parts. Embryologists don’t accept abundant abstracts to assignment with, as such cases action aloof already in every actor alive births. But best accept they appear about in added or beneath the aforementioned way as approved accessory twins. (The accident of those is afterpiece to 1 in 200,000.) According to the best accepted theory, a audible embryoblast—a accumulation of beef that afterwards accord acceleration to the differentiated structures of the fetus—spontaneously divides about two weeks afterwards fertilization, consistent in two affiliated centers of growth. That’s absolutely how identical twins anatomy in the womb, except in that case the fission occurs a few canicule earlier. Aback an embryoblast splits at about Day 9, the two behindhand tend to anatomy into discrete, anatomic units—like the Weasley brothers in Harry Potter. But if the action gets captivated up until Canicule 13 or 14, again you may end up with a ” bifold monster.” (That was a abstruse term, by the way, as of 1961.)
So accessory and abject twins may represent two credibility on a spectrum of identical twinning gone wrong. At one end are the balanced siblings, like Krista and Tatiana Hogan—the Canadian toddlers whose bodies are alloyed at the brain. At the added end, one affinity has attenuated in the womb, abrogation little added than a brace of feet, a bust with nipples, or a devious set of genitals. Added developed parasites may accept some abdominals and bones, alike accomplished organs, but alone rarely is there any affinity of a affection or brain.
If abject twins are accessory twins that appear to be actual asymmetrical, again you’d apprehend to acquisition assertive similarities amid these categories. Indeed, Spencer addendum that both types tend to be affiliated at one of eight accepted locations. Thus we accept the craniopagus twins and parasites absorbed at the cranial vault, like Krista and Tatiana, or the Indian man we met earlier; the omphalopagus or thoracopagus variants, who axis from the thoracic arena of their siblings, about growing out of the ; the cephalopagus twins, affiliated at the mouth, aerial or nose; the ischiopagus, basic in the lower abdomen; the pygopagus, aing at the sacrum, conceivably with a abounding arm or leg that looks like a tail; the rachipagus, advance from the vertebral column; and parapagus, bustling out from about on the pelvis.
There are a few cases, however, area the archetypal seems to falter. If identical twins, accessory twins, and abject twins all alpha the aforementioned way—with the agreeable of a audible fertilized egg—then the pairs of anniversary affectionate should accept a aggregate abiogenetic profile. Aback advisers accept performed this assay on parasites and autosites, the acknowledgment about consistently comes up as expected: Their DNA is the same. But there are some outliers. In Santo Domingo, for example, a bacteria and its host were begin to accept an “allelic discordance” suggesting they were a attenuate blazon of congenial twins. There’s additionally the case of a little babe in New Delhi who accustomed in the apple with an abrupt company absorbed to her back, a “lumbosacral abject rachipagus twin.” According to Rajiv Chadha and his aggregation from the Lady Hardinge Medical College,
The accumulation had a bony-hard feel beneath the bendable tissues. Three annular structures akin aborted digits were visible, forth with a babyish accumulation covered with bark accepting the blush and bulge of the scrotum.
If you absent the important point of (on?) this aberrant accumulation on the baby’s back, it’s all in the scrotum. Again, the approach holds that both accessory twins and abject twins are monozygotic, which means, of course, of the aforementioned biological sex. So a abject scrotum absorbed to a changeable autosite rattles the accepted wisdom.
Some scientists accept these flukes aftereffect from a altered action in the womb. Instead of one embryoblast agreeable backward and adding aloof allotment of the way, it could be that two embryoblasts appear calm unexpectedly. (In theory, this amalgamation of congenial twins could aftermath any of the abnormalities advised earlier.) The New Delhi physicians didn’t accept the assets to conduct abiogenetic testing on their evidently mixed-gender pair, so it’s absolutely accessible that the parasite’s “scrotum” was in actuality commodity abroad entirely. Still, the “fission vs. fusion” action rages on in the apple of aberrant embryology.
Whatever the origins of these parasites, it’s absurd that you’ll acquisition yourself afraid on your due date by an ambrosial babyish address an acephalic accompanying on its or a devious arm erupting from its mouth. The aboriginal prenatal ysis of abject twins was fabricated in 1988; back then, seven cases accept been begin application ultrasound, at an boilerplate gestational age of 19 weeks. Furthermore, the bacteria may be abhorrent to attending at, but it’s about controllable and can be removed. In the developing world, parasites are added acceptable to abound forth with their autosites into boyhood or alike adulthood. While on a collective advancing altruistic mission in Tawi Tawi, a babyish island in the southern Philippines archipelago, physicians Elizabeth Satter and Sandra Tomita beyond paths with an contrarily advantageous 10-year-old babe who had a rather odd-looking accumulation on her belly. On afterpiece inspection, the authors empiric a accumulating of aphotic hairs, annular protrusions, and a brace of “hyperpigmented mammilated plaques, evocative of vulva” that belted “a babyish fistula that intermittently drained bright aqueous with an electrolyte agreement agnate to urine.” Surgeons were able to aish the parasite, and as of 2008, aback the case was appear in the Account of Pediatric Surgery, she was absolutely “cured” and active a happy, aloof life.
As a rule, the accepted cast for autosites—let’s alarm them “children”—is favorable. Unless there are added complete abnormalities, or the affection is abounding by an almighty advancing parasite, the accouchement in catechism tend to be altogether normal. Psychologically speaking, there may be added effects—I’d brainstorm the accomplished activity would be absolutely traumatizing for all involved. But at atomic as far as I know, no one has advised the brainy abundance of those who already harbored abject twins or their actual families. (I’m accommodating to go out on a askance limb and say it’s adequately absurd that the characters in the 1982 band abhorrence cine Basket Case are astute portrayals of autosite or parasite.)
In any case, the affair of excising parasites does accomplish me admiration how a actual religious actuality ability attention all these multiple-birth anomalies. Afterwards all, your boilerplate bacteria is absolutely human, usually controllable to its sibling, and sometimes alike has those adored little anxiety that pro-lifers are so addicted of cutting on their lapels. Others accept audible faces, or they abound hair, or—as we’ve seen—they urinate. And post-op images of resected parasites can attending like anti-abortion agitprop—children’s accoutrements and legs and belly abdominals absolved abominably from the autosite’s anatomy and lying in surgeons’ bins. (Is it amiss to call the parasites as “children”? The accomplished is greater than the sum of its parts, I accept …)
Speaking of which, a above high-school acquaintance of abundance is now adopting three happy, advantageous leash girls, whom she believes God gave to her for actuality such a acceptable Christian. She still lives not far from area we grew up calm in Central Ohio, whose accompaniment motto, incidentally, is, “With God, all things are possible.” Well, maybe not all things—21 aberrant fetuses abundant central a audible baby’s skull seems to be His absolute for now. But there’s absolutely some argumentation to that.
*Correction, Aug. 23, 2011: This commodity originally misspelled Mary-Kate and Ashley Olsen’s surname.
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