Human Chimerism: Mindboggling DNA Tests Gone Wrong-Guest Blogger

24 Jun

In Greek mythology, a chimera is a strange, monstrous creature having the body of a lion, the head of a goat arising from the spine, and a tail that ends with a snake’s head. Such a creature would perhaps be the only apt moniker of an anomaly that exists in real life. Chimeras are animals that have at least two different groupings of varying genetic cells. These groupings have their source in the different zygotes present during reproduction. More common among animals, human chimeras, however, do exist, albeit they are phenomena that is extremely rare.

Most human chimeras will never know that they are chimeras, unless, that is, a DNA test is involved. Only 35 Americans have been identified as having chimerism, and in only two cases involving DNA testing did chimerism become a head-scratching problem for scientists. Still, chimerism has caught our imagination, as it has been featured in CSI and other popular TV crime shows.

There exists two different types of human chimerism–microchimerism and tetragametic chimerism. In microchimerism, only a small part of the body has a different cell line, while the rest of the body is uniform. With tetragametic chimerism, there may result several patches of inconsistent sets of DNA. Human chimeras at times, but not always, manifest themselves as hermaphrodites.

The two cases in which chimerism became problematic involved DNA testing. In one case, a woman named Lydia Fairchild became pregnant with her third child. During a routine DNA test to determine the receipt of welfare funding, the results revealed that every relative was related to the newborn except the mother herself. Fairchild became involved in a suit that both denied her social support and accused her of fraud. Eventually, Fairchild’s lawyer discovered an article in The New England Journal of Medicine, in which a similar case was documented involving a chimera and a DNA test for a kidney transplant.

While human chimerism is a phenomenon that is so rare it’s almost negligible, the fact still remains that DNA testing, while extremely accurate in the crime lab, is not infallible. To learn more about chimerism, read Vivienne Lam’s article in the Science Creative Quarterly.

This guest post is contributed by Jessica Cortez, who writes on the topics of online degree programs.  She welcomes your comments at her email:

Note from DP Lyle: Want to know more about Chimerism?

Suite 101 article

Bright Hub article


Posted by on June 24, 2010 in DNA, Guest Blogger, Medical Issues


11 responses to “Human Chimerism: Mindboggling DNA Tests Gone Wrong-Guest Blogger

  1. john stover

    March 22, 2012 at 10:24 pm

    I hope you can help me, I had an overseas relationship, actually we have been married a yr now, we had a baby together almost two yrs ago, I have always completely trusted her, and she swears up and down that there is no way she cheated on me, and I beleive her, plus this child has so many charistics of mine, some that even resemble my dad, yes the child looks alot like mother in face, by the way she is filipino, spanish mix, Im indian irish german mutt, embassy wanted dna for U.S. citizenship, I didnt think it was exactly required since we had a lot of proof of our relationship before pregnancy, I think since child not look like me in the face, so i will play along, we are in U.S. child with her mother, it takes a lot of shipping of things, test done in misssiouri, im in kansas, anyway, first test say she the mom, im not father, i say i never beleive that, so i look into this charmerism, well we come up with doing my parents, no success either, they said that rule out being chamerict, i still will never beleive all these results, my wife says that they have had in past blood tests that would not matchup in her family and or relatives that just had to be wrong, i will never ever beleive this child is not mine and it is about killing me with these results, not been to good for her either, she has always been so confident with all this, and beleive me, we have talked alot about this, there just would be no reason for her to keep living a lie


    • D.P. Lyle, MD

      March 23, 2012 at 12:03 pm

      John—For Medico-Legal reasons I never comment on real life situations such as this.


      • john stover

        March 23, 2012 at 11:28 pm

        well we could pretend this is a scenerio


      • D.P. Lyle, MD

        May 3, 2012 at 4:37 pm

        Yes, you could. But it’s not so I won’t.


  2. Trey

    May 3, 2012 at 10:58 am

    I have two questions; I am a fifteen year-old male child who, in the womb, had a twin of the opposite gender that died at birth; since I’ve been having gender identity “issues” for multiple years, know about human chimerism, and had a twin of the opposite gender, is it possible that my dysphoria is the result of me being a chimera? And is there a way to check?


    • D.P. Lyle, MD

      May 3, 2012 at 4:35 pm

      Anything is possible but I’ve never heard anything about chimerism having such psychological effects. Doesn’t mean it’s not possible just not likely. Your best bet would be to see a geneticist—someone who specialized in genetic disorders. Ask your own MD and see if he knows one in your area.


    • JNE

      November 14, 2012 at 4:21 am


      I am neither a doctor nor a medical professional, but you really do need to know about this, and I have experience with both issues. YES, in fact, dual-gender chimeric situations can in fact leave an imprint on the mind. It’s not just the mind: it could be your hormones or any number of things. If you’re struggling with this issue, you deserve to get help from somebody who knows what you’re going through. Been there.

      Now, I may have chimerism of a different sort, but I know a woman who, the long version I originally wrote out for you gone short, is a chimera, XX/XY. She happens to be of a lesbian sexual orientation, but that is completely irrelevant to gender identity. While yes, I know, labels for sexual orientation are designed around gender, they’re totally different things. Her sexual orientation remained the same when she made a transition to male with no surgery, nothing, and lived in a small town in Northern Maine as a man legally married to a woman (she changed her status from F to M in California before leaving and her name to something rhyming with her female name) for seven years. She, living as he, was even the lay minister of their church.

      My friend developed secondary sex characteristics of a male. She noticed it one day and panicked. She was in the endocrinologist’s office about as quickly as she could possibly be, getting her hormones checked. The doctor said that her testosterone level comprised 85% of her hormones and that her estrogen level was undetectable. Now my friend, a mother of three children, panicked and it took her seven years to accept. Having excellent medical records because of having formerly been married to a military man for twenty years (who knew about her latent lesbian orientation and was a gentleman about it), she eventually contacted Johns Hopkins, who told her that their best guess, and this was having gone over everything available, was that she was a chimera of the same situation as you but that she had a brother twin that died in the womb whose genetic information she absorbed.

      She’s now again living as female. Its a long story with a simple reason. She often gets mistaken for a man: my own father assumed that she was male. She does have facial hair and has to shave, and she, like many gender variant people, deals with some nasty behavior from hateful people sometimes. Lacking a uterus due to a hysterectomy and not having testes, she still has a hormonal profile more like a man. She doesn’t like dressing in female clothing: she dresses in male clothing. Otherwise she feels like she’s in drag: badly. She was an extremely successful gender variant person: oh, the gender dysphoria! It’s quite a journey.

      There is absolutely nothing wrong with you. I know exactly what you are talking about. I have been through gender dysphoria. I am not XY/XX but if you are, it could certainly have an effect on you. While something is indeed causing your gender dysphoria, it is not a disease unless you want it to be. If you’re comfortable as you are or you could be comfortable as you are with a little modification but remaining gender variant, then you should be. That’s the truth.

      I know lots about both topics, having lived with this friend, who is old enough to be my mother, and having undergone issues myself about gender dysphoria and chimerism of a different kind. I hope I can be of service to you. It’s not everyday I meet a younger person (I’m about ten years older than you) whom I could know exactly what to tell. I hope you’re not struggling. If you are, it’s okay. The point is to be yourself.

      You don’t have to cure yourself of being gender variant. In my case, I had Low Testosterone, but that’s not the root cause. i think my brain is fundamentally wired more like my mother’s than my biological father’s. The latter could be plural, to add insult to injury with a paternity crisis. It’s one form of chimerism.

      I’m not saying under any circumstances that you will morph into a lady biologically, but my friend has no testes and never has and yet is man-like: somewhere in the middle of the two. She didn’t need hormones to pass as a man: only a pinch of testosterone for good measure. Your hormone levels could be different than the average cisgender male. (That’s a strange word meaning a male whose identity aligns with both their being male and feelings of masculinity.) But look at me: I had Low Testosterone, otherwise, my body was perfectly normal in its maleness, producing testosterone and not converting it to pseudo-estrogen. It just wasn’t producing enough of it. But I have experienced profound gender identity issues in the past. It’s just not nearly as bad with a testosterone supplement. It works for now, because I can focus on what I have to do to survive. Will I want it forever? Will I be able to support it forever financially? I don’t know.

      Do what’s right for you and never hesitate to ask questions. Your gender variant-ness is not a disease: it’s a part of you. Gender dysphoria, on the other hand, can be distressing. I know a lot about having to handle this, having learned in a lot of isolation in an environment I didn’t need to be in. YES, if you’re chimeric in your biology, it could be a part of it. I most recently lived with somebody that happened to. But don’t worry. The body is a very interesting thing: surprises happen everyday. If you’re uncomfortable, do whatever it takes to become comfortable, whether that means getting rid of the gender dysphoria (it may never completely go away but in my case has all but subsided completely: I still don’t feel the intoxicating sense of masculinity I could work myself into before sometimes) completely or finding somewhere in the middle.

      You’re co-gender, kid. I prefer that term to the California term, “bigender,” that I learned from my friend. You’ve got the rudiments of both in you and that is a wonderful thing. Indigenous North American cultures would have honored you for this. I know because I come out of one, and then hard-core European immigrant culture at the same time. I know the difference. I want you to make it your mission in life to be comfortable with who you are, even if you don’t see anybody in front of you who is like you. They’re out there. I can identify. Hang tight.


      • Dan

        July 3, 2013 at 12:34 am

        I have a question although it may be a stupid one…I’m not sure. I read about signs of chimerism or w/e and it mentioned things like different hair colors, different eye colors and even different skin colors. Are there any more signs that are more conclusive? I have noticed patterns about myself that like an abstract symmetrical themed having 2 or more of a lot of things… like the same but different. Hard to explain but I will try. I am ambidextrous, blood type ab+, 2 colors in my beard and a third color hair on my head that is the same color as my leg hair and my arm hair is lighter which makes 4 colors. I found 2 grey hairs on my chest but I know that’s gonna be normal so I wont say 5 natural colors. I’m like freakishly flexible despite normal muscle mass, skin is super stretchy. I’m bisexual if that means anything although at the moment I have a girlfriend and I slightly prefer women. She gets me cuz shes bi and slightly prefers men. I even view the world around me oddly. I can read and write up side down and or backwards. Normally when using my left hand I write words starting from top to bottom left to right and with my right hand I write bottom to top right to left although if it try I can switch this also. I can even write the letters backwards to form sentences only view able in mirrors. I draw with both hands at the same. Every single person in my family needs glasses and I don’t… goes back both sides of my family for literally all of them. On a side note my hands are odd too. My ring and index fingers are exactly the same length and my little fingers actually point away from my the rest of my fingers a little but when I bring my fingers together they are straight like the rest but my little fingers can move a little side to side for a wider grip on things. I notice on other people there ring and index fingers are always different lengths from each other and in regards to the little finger that they are usually straight and or rarely pointed towards the other fingers. Are any of these things bringing any conditions to mind? Or am I just weird and a handsome mutant? Lol, no but seriously could I be some kind of chimera? Sorry I made you guys read so much 😛


      • D.P. Lyle, MD

        July 3, 2013 at 7:48 am

        The signs of chimerism are many and usually subtle. The only way to prove it exists is through genetic testing.


  3. Dan

    July 3, 2013 at 2:47 pm

    That sounds expensive and if I told my doctor I may be one of the forms of chimera I think he will just take me for crazy. I did a bit of reading and I may have something called Ehlers–Danlos syndrome type 2. And my blood typing seems normal seeing how I have an A parent and a B parent. In regards to my ambidextrous and strange reading and writing I learned my grandmother was left handed then beaten (as many kids where back in the day) into using her right hand and became ambidextrous that way so maybe there is some epigenetic factor with that bit… I don’t know. Would I have any reason to get a gene test that insurance would cover if there a test to see if I have Ehlers–Danlos syndrome? And if I got a test of this sort could they stumble upon chimerism? I’m in a part of maryland that is known for gene research so any chance may be in my favor. I’m just not knowledgeable enough about this stuff and all I know if from the Internet basically and we know how reliable that can be when we forget to check references. If I’m off topic a bit feel free to email me with whatever you do not wish to post here. Thanks boss.



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