Conjoined twins, how boundless is nature's depravity!

This post is about all kinds of ways humans are born wrong. It's very disgusting and scary. Personally I powered through the study by listening Depressive Suicidal Death Metal. Here's the playlist I used. I won't show gory pictures but I would link them. Please don't click them unless you eat Cupcakes for breakfast at the Rainbow Factory. They really put the "gross" in "gross pathology".

But first, why do I bother with this? There's a philosophical point to be had here. Usual humans move about fully formed and independent, it's easy to imagine them to be naturally individuals. They aren't and looking at how grotesquely their individuality can fail is a great way to shock one into realizing the mess of reality.

And there's an even higher way to look at this. The body is not a sacred ONE thing, it's just a sack of meat... Similarly, the mind is not a sacred ONE thing either, it's just... a messy collection of things that a brain does, like in Inside Out (2015). Once this is appreciated, one might see that an indivisible individual "self" is an illusion.

Last chance to pull out of my terrible trip into the chaos of reality, you can read a Slate article instead, which is a lot tamer than this, I feel.

A spectrum of conjoinedness

We define a conjoined twin to be a body that is made from the merger of a pair of twins during pregnancy. There are many ways for that to happen:

Chimerism - Vanishing twins - Parasitic twins - Conjoined twins - Separated twins

Chimerism

Chimerism is when the cells merge together and grow into a normal body so perfectly that it seems normal, except that the DNA of the cells in the body come from the twins. 

Such cases are invisible, except in the very unlucky cases like Lydia Fairchild, where the DNA relationship tests caused great confusion.

Note this is different from "mosaicism" (aka "somatic mosaicism"), which is when all cells in a creature comes from a single zygote, but some cells have different DNA from mutations. This for example, happens for cancer cells, but not just cancer. Turns out EVERYONE is a mosaic! See, for example, this report (perfectly safe and quite fun to read) Every Cell in Your Body Has the Same DNA. Except It Doesn’t.

In 2017, researchers whole-genome sequenced white blood cells from 241 adults, and identified 163 early embryonic mutations.

In 2015, researchers whole-genome sequenced 226 neurons in the brain of a 17-year-old male, and found that they have "family trees" at least five distinct clades, suggesting that there were five big mutations in the embryo early in development and they gave rise to the five clades. The researchers also noted that, since each neuron lives for many years, during the years, its DNA would continue to mutate, thus every human brain neuron has a profoundly distinctive genome, harboring as many as 1500 mutations due to the mutations throughout its life.

 A 2016 report reports a case where an infant has two clades of cells in her heart, one of which has a bad mutation in SCN5A gene, causing the whole heart to fail.

This is also different from microchimerism, which is when some cells from other creatures enter the body of a creature already born. Most common case is when a female mammal gets pregnant, and a some of her fetus's cell enters her own body.

Bizarrely enough, microchimerism has been used as propaganda tool against woman having multiple male sex partners.

Vanishing Twins

Humans are not made for multiple births. About 60% of twins are prematurely born, and almost all triplets and above.

Fetus papyraceous is the case where the vanished twin doesn't get absorbed, but "squashed" flat and mummified dry, like a Corpse Party paper doll. According to Fetus Papyraceus: A Rare Case Report (2017):

a mummified fetus occurring in multiple gestations where one fetus dies in utero and is incorperated between the uterine wall and the membranes of living fetus. Intrauterine fetal demise after eight weeks gestational age in a twin pregnancy, with retention of the fetus for more than 10 weeks will result in mechanical compression of the fetus, making it look like a parchment paper. Fetus papraceus is usually discovered among the placenta and membranes of its welldeveloped twin.

Technically, after the twin has died, but before it has been turned into a paper doll, the twin is called a fetus compressus.

Fetus compressus is a stage in the process of degeneration of the fetus that dies in utero, as maceration occurs, together with autolysis of the internal organs, so the fetus collapses and becomes flattened... 

The incidence of this condition lies between 1 : 184 and 1:200 twin pregnancies.

The hypothesis is that the flat baby keeps its human shape because the flattening happens after its bones are developed. This can be quite clearly seen in a Mütter Museum specimen.

Someone noted that according to some text in the Talmud, a pregnant woman can use contraception during sex, because ancient rabbis thought twin pregnancy resulted from two separate acts of conception, and that fetus papyraceous resulted from one twin “killing” the second, therefore it was advisable to use contraception to avoid twin pregnancy altogether.

Parasitic Twins

It's like conjoined twins, but one of them is undeveloped, called "parasitic", and the other is (mostly) developed, called "autositic".

Craniopagus parasiticus is the case where the parasitic twin is only a head, fused on top of the autosite's head.

Fetus-in-fetu (FIF) is when the parasitic fetus is stuck inside the autositic fetus, or "calcified intra-abdominal mass in the newborn infant". Over 50 cases of fetus-in-fetu have been reported since 1800. It has an incidence of about one in 500,00 live births. Sometimes there can be more than one fetus stuck inside. Sometimes the parasitic fetus is made of only a few limbs and organs, or even just a mass of tissues like a teratoma. The autositic twin sometimes can develop rather healthily.

One report in particular describes a case of two fetuses stuck in the head of one fetus, in alien-like detail. Intracranial fetus‐in‐fetu with numerous fully developed organs (2017):

triplet FIFs at 31 weeks within amniotic‐like sac in the fetal skull, consisting of multiple well‐defined organs. The FIF attached to the host twin via body stalk containing a single main feeding artery and vein, representing umbilical vessels... Pathological examination showed the triplet FIF, consisting of numerous well‐developed organs, with soft tissue/skin coverings, but no vertebral body...

Twin reversed arterial perfusion sequence (TRAPS) is when the parasitic twin entirely relies on the other twin for blood supply instead of taking it from the placenta, and usually the autositic twin is healthy. Its occurrence is 1% of monochorionic twin pregnancies, and in 1 in 35,000 pregnancies overall.

The parasitic twin doesn't have a heart or a head, thus also called "acardiac", and receives blood supply from the host twin by an umbilical cord-like structure. The healthy twin is thus called the "pump", because it pumps blood for the acardiac twin. The pump twin often survives and develops normally.

Conjoined Twins

Siamese lamb, copperplate. Van Doeveren (1765). Leiden University Library

Conjoined twins are quite mild in comparison, and quite many of them are survivable. Most cases don't pose philosophical problems, except when the twins share a brain, or have significant connections between their brains. Are they one or two persons? It's almost like a split-brain person...

Of interest is that there's a full taxonomy of conjoined twins. It's made of latin, as usual.

One particular disturbing version though, is the janiceps, which has two faces on the same head, but grown in a very bizarre way that can only be explained with a picture. See A case of conjoined twin's cephalothoracopagus janiceps disymmetros (2008) for details.

Separate Twins

No problem at all here!

Finally something cute!

Miscellaneous

I found some other strange things during composition of this post.

Abortions storm

Turns out that it's normal for female sheeps (and other ruminants) to just get abortions for no apparent reason. The usual rate is 1-5%, but sometimes it gets higher, and that's called an "abortion storm". It sounds very dramatic. Should be a metal band name.

Prenatal psychology

While searching for statistics about the rate of death of one of a twin in the womb, I came upon some people who describes grief for their twin that never even got born and were instead squashed flat like a paper doll, or died before that and got completely reabsorbed. 

I thought it's amusing, but can understand. People gets really attached to fictional "what-ifs", especially when it's something friendshipful like a twin sibling.

But then it got super weird when I came upon The Vulnerable Prenate (1995) that quite literally claims that fetuses are conscious and can be proved by hypnosis therapy that made people remember their days in the womb. It really made me laugh when it started quoting the Bible and claimed that Christ's life was a metaphor of implantation (the embryo adheres to the wall of the uterus). And similarly there were "wombtwin" people who thought twins can play and bond in the womb.

Ethics of brain-damaged babies

Like nations that constantly scuffle at their borders, ethicists scuffle at the borders between persons and unpersons. Nobody currently regards a baby completely without a brain as a person, but a baby with significantly incomplete brain is a serious border case that caused lots of scuffles.

There was Baby K case where a baby got anencephaly , 

A baby born with anencephaly is usually blind, deaf, unaware of its surroundings and unable to feel pain. Although some individuals with anencephaly may be born with a main brain stem, the lack of a functioning cerebrum permanently rules out the possibility of ever gaining awareness of their surroundings. Reflex actions such as breathing and responses to sound or touch may occur.

Note: when researching about this, not only must you have a strong resistance to gross pathology, you must also prepare for anti-abortion propaganda, usually in the form of "This baby was born without most of the brain, and is still pretty functional as a human [in varying amounts]. Therefore all anencephalic babies must not be aborted." They never do a cost-analysis/triage though.

Worst stargazing ever

Iniencephaly is a cephalic disorder where the baby has no neck and the head is fused to the torso and bent upwards, nicknaped a "stargazing head". It has a rate of 0.1 to 10 in 10,000 deliveries. No standard treatment exists and almost all cases results in immediate death.

India

For some reason, a lot of the medical reports I read came from India. Is it because India has a particularly active medical report system?

A joke

The articles kept saying this and that fetus got "delivered", and I wondered out loud, "Who ordered them?"