About once a month I respond to someone online who claims that only girls can have Turner Syndrome. Some suggest that Noonan Syndrome is the male equivalent. Sadly, they often get such misinformation from a genetic counselor or physician. Although Noonan Syndrome results in some of the same medical issues as Turner Syndrome, it is caused by mutations in the PTPN11, SOS1, RAF1, KRAS, NRAS and BRAF genes rather than the loss of a sex chromosome.
>>Noonan Syndrome
The Genetics of Turner Syndrome
Turner Syndrome is caused by the loss of a sex chromosome during the first few cell divisions of a human conception. Ordinarily, each cell has 46 chromosomes–22 pairs of autosomes and two so-called sex chromosomes. Usually male is 46,XY and female 46,XX. When one of the sex chromosomes is missing in all cells, the karyotype is written as 45,X.
Cells need all 46 chromosomes to function properly. Indeed, the only chromosome that a cell can live without is the Y or the second X. It is the lack of a second sex chromosome that causes the developmental issues in Turner Syndrome. Most 45,X babies are stillborn. Some speculate that all of those who survive have at least some cells with two sex chromosomes. Current technology doesn’t allow us to determine the genetic makeup of every cell in the body. A karyotype is usually based on 25 cells from a blood sample. The rest of the cells in the body may be different.
Genetic Mosaicism
When only some cells are missing the second sex chromosome, the karyotype is written as 46,XY/45,X or 46,XX/45,X or something similar. This is called mosaicism. As I said, some speculate that all Turner Syndrome babies who survive have some mosaicism.
The degree of mosiacism varies over time because the 45,X cells don’t reproduce at the same rate as the other cells. The degree varies from person to person. What matters is where the 45,X cells are during fetal development. A woman with as little as five percent 45,X cells in her blood may be born with streak ovaries and be short statured as an adult. Or she may have no medical issues related to Turner Syndrome.
Y Chromosome Mosaicism
A woman with Turner Syndrome may be missing an X or a Y chromosome. What if she has mosaicism?–and she has a Y chromosome in some cells? Her karyotype would be written as 46,XY/45,X or perhaps 45,X/46,XY. But 46,XY usually results in male. So what determines whether the mosaicism results in a boy or a girl? Again, it’s where the 45,X cells are during fetal development.
46,XY/45,X can result in a baby with male genitals, female genitals, or somewhere in between. It can result in any of the medical issues commonly associated with Turner Syndrome.
>> 45,X/46,XY Including Y Chromosome Rearrangements (Great pamphlet from Rare Chromosomes site)
>> The Phenotype of 45,X/46,XY Mosaicism
>> X/XY Chromosome Mosaicism: Turner Syndrome and Other Clinical Conditions
>> Turner’s syndrome in the male with chromosomal mosaicism
>> Turner’s syndrome in the male (Br Med J)
>> Turner’s syndrome in the male (JAMA)
I knew a boy with a 46,XY/45,X karyotype who was taking growth hormones. I know a woman with typical Turner Syndrome features who has the same 45,X percentages as the boy. On rare occasions, 46,XY/45,X identical twins have been born one male and one female.
>>Monozygotic twins discordant for sex
>>46,XY monozygotic twins with discordant sex phenotype
On A More Personal Note
My karyotype is 46,XY,22qs+/45,X,22qs+. The 22qs+ is an exceedingly rare improperly-satellited autosome. Let’s ignore that for now. Without it, the karyotype would be 46,XY/45,X. Or XY/XO for short. Turner Syndrome mosaicism.
My Turner Syndrome mosaicism gave me mildly malformed kidneys and heart valves. I’m hypothyroid. I have visuo-motor and spatio-temporal deficits. My joints were hyperextensive. (Check out my left leg in the photo above.) I have the pixie face common to Turners, due to my small jaw. I was cross-eyed as a child. My ears are set low. I was the smallest of my peer group until fifth grade. At nine, I wore size 6x clothes. And my puberty came out of a bottle.
The vast majority of children with a 46,XY/45,X karyotype are born with normal male external genitals. Of those, more than a quarter have gonadal anomalies. Some will require growth hormone. Some hormone replacement therapy for sex development.
>> The Phenotype of 45,X/46,XY Mosaicism
What was between my legs wasn’t typical female. I was raised as a boy. I wasn’t typical male either, though, and took estrogen for my sexual development. This is the nature of intersex conditions. I find it, at times, mildly amusing that some might think I could only have Turner Syndrome mosaicism after surgery to make my genitals more typical of a girl.
thanks lianne for informing the world with this. I have xxy chromosomes, intersex, intergender and an individual like you lianne, thanks again for bothering to make a difference
Thanks for sharing this information.
I’m in my second year of university and I’m studying psychology. In my genetics handbook, we learned that all turner patients are girls (because all boys die before birth). We also learned about mosaicism, so it didn’t really make sense to me that someone with karyogram 45,X must be female, especially since most people with Turner syndrome have the X of the mother (which doesn’t determine the sex). It just didn’t seem right to me that someone with karyogram 45,X or 46,XY/45,X would be considered a girl, simply because this person looks like a girl. Isn’t he/she supposed to be a boy, and therefore not all turner patients are girls, they just look like girls?
So my point is: shouldn’t we say “Turner patients are people, male and female, who have lost their second sex chromosome and therefore only have one X chromosome, and therefore will be born as a female”, in stead of “all Turner patients are girls, all boys die before birth”?
Or is this incorrect?
God created a wonderful diversity of biological sex variations. We map those into male, female, and intersex. Most males are XY, but not all. Most females are XX. XO–Turner Syndrome results in a child with female genitals. But some babies are mosaic–they have XO in some cells and XX or XY in other cells. A child with XY/XO mosaicism can be born with female-typical genitals, male-typical genitals, or ambiguous genitals. They can also have any of the medical issues that are common to Turner Syndrome.
A woman with the complete form of Androgen Insensitivity Syndrome will have XY chromosomes, female-typical genitals, and testes in her abdomen rather than ovaries and uterus. If the doctors don’t remove her testes, she can have a normal feminizing puberty, but without getting her period. She may not be able to carry a child, but she’s still female. Even with XY chromosomes and testes. A woman with CAIS could go through her entire life without knowing her condition’s why she never got her period.
This is what my daughter has. She is geneticly x with a damaged y. Had streaky gonads that were removed. She is visually female in every way. Needed growth hormone and is now on hormone replacement. She is very femininem. But no matter what she is loved and accepted to be whatever she chooses to be.
A child with a full 45/XO karyotype will always be female in the human race. In other animals that is not the case. In humans, the X chromosome carries hundreds of genes different from those on the Y chromosome. There are only a few genes which are shared between the X and the Y. Nevertheless, since the Y carries the genes for male determination, when a full XY karyotype is present in humans, the male sex will always predominate. However, an XO human has to be a girl. The only way that an XO human has male genitalia is when the male determining genes are present in another chromosome or when the child is a mosaic XO/XY.
It’s a bit more complicated, actually. Most babies who are ‘pure’ 45,X are stillborn. Although we can measure mosaicism in the blood or in some particular tissues, we don’t have a way to accurately measure it in the entire body. So we can’t definitively rule out mosaicism.
Yes, a full XY karyotype ordinarily results in a male phenotype. But a number of genetic mutations exist (e.g. Complete Androgen Insensitivity Syndrome) which result in a female phenotype in an XY individual.
Although the majority of children who have an XY/XO karyotype have a male-typical phenotype, a small percentage have a female-typical phenotype, and a small percentage have ambiguous genitals. And even those with a male-typical phenotype often have atypical gonadal development. (see the Chang, et al article linked to in the post)
Any of those with an XY/XO karotype can also have any of the medical issues commonly associated with Turner Syndrome. And, as I mentioned above, a small percentage will have a female-typical phenotype. The insistence on a female-typical phenotype for a diagnosis of Turner Syndrome is politically driven rather than medically.
Thank you for your feedback!
Go to this link. This man has significant features similar to women diagnosed with Turner syndrome. https://m.facebook.com/RealDLHughley/photos/pcb.2762277380481248/2762276997147953/?type=3&source=48
Thank you so much for this website and for you! My son is now 14 1/2 years old, and we have been seeing numerous physicians at the Cleveland Clinic for years!! My son has 46 XrY/45XO mosacism with SHOX deletion, hypothyroid, growth retardation, normal male phenotype and normal sexual maturity with infertility (we’re told, and the little ‘r’ in his karyotype is for ring). I have always known something was amiss with him, but it took several physician changes and by the time he was 9, I found one who believed me and ran a battery of tests. His hypothyroid led us to endocrinology, and that then took us to a wonderful geneticist. This has been a rough 4 years, with so little information available. He’s been receiving growth hormone injections for the past 4 years, and he’s grown only 21 cm, which leaves him under 4’10”, with closed growth plates. He’s a smart kid with a great sense of humor, except when it comes to his diagnosis. I hope that as he becomes closer to adulthood, I’m able to find some more support out there for him. It’s hard to be diagnosed with such a rare condition, one that is so understudied, and not understood. So again, I thank you for putting yourself out here, and given support!! God Bless!
Hi- I am trying to find out more about the 46 XrY/45XO mosacism. We recently lost our baby who also had severe cystic hygroma and hydrops. I am trying to find out is this type of mosacism inherited and can it repeat itself? Thank you in advance for your response. There isn’t enough info on this and I am trying to find out as much as possible.
I am currently 19 weeks pregnant, and my baby has been found 45XO/46XY, and doctor told me, the baby looks like a boy from ultrasound scan. But from the CVS and amnios, 90% of the cell is XO, only 10% is XY. I have consulted several doctors, but none of them told me what will happen to me baby as it is a rare condition. My family want me to give up the baby, but I personally don’t want to do so. I am so confused, I don’t know what will be my baby’s choice, what should I do?
Thank you Lianne for these details. I study medical laboratory technician and today I was looking for more about Turner syndrome and I thought – did a boy can have Turner syndrome?
It’s still strange to me, how can a human with 46XY/45X0 can have female characteristics? Girls with Turner syndrome aren’t best developed, so according to that, humans with Y chromosome shouldn’t have female characteristics either. When zigot is created, it had XY chromosomes still, so I think he’s missing Y chromosome, so it’s not exactly Turner syndrome, If a guy has Turner syndrome, he would had 46XY/45Y mosaic syndrome.
Maybe I wrong, I don’t know. It’s just my opinion for now, I hope I will found out more about these syndroms.
Turner Syndrome is caused by the lack of a second sex chromosome. A girl with Turner Syndrome can be missing an X or a Y. And Professor Skuse has found that there are subtle differences between the two.
A girl with the pure form of Turner Syndrome will be missing the second sex chromosome at conception, or at least prior to the first cell division. Almost all of these girls are stillborn.
The mosaic form of Turner Syndrome can result from the loss of a second sex chromosome during the first few cell divisions. From that point on, there are two different cell lines in the body. One is XO–Turner Syndrome. The other is XY or XX. This is called genetic mosaicism. Or, more specifically, Turner Syndrome Mosaicism.
An embryo that has some XO cells and some XY cells can turn out Turner Syndrome female, normal male, or any mix of the two. It depends on where the XO cells are during fetal development.
An embryo that has some XO cells and some XX cells can turn out Turner Syndrome female, normal female, or any mix of the two. It depends on where the XO cells are during fetal development.
The original definition of Turner Syndrome only dealt with females of short stature and a lack of sex development. Boys who have an XY/XO karyotype can have any of the Turner Syndrome features that an XY/XO girl would have. Less the genitals, of course. Most doctors stick with the old definition, even though if often means the boys don’t get the proper testing that they would were they girls.
I understand this thread is a few years out so I’m hoping this message finds you. I stumbled into this page while researching about 45x,46xy. My unborn baby was diagnosed with having 45x,46xy mosaic and I’ve been having a hard time trying to understand what this really means outside the medical explanation given. The genetic counselors mentioned that not all cells were 45x46xy and only 4 came back with this results. Again, it was hard to understand what this meant in the greater scheme of things.
Through ultrasounds, the baby is developing normal and according to the doctors, is clearly a male where all the developing parts and organs are normal. However, the genetic diagnosis is keeping me up at night.
I was hoping you could provide some insights as to what 45x46xy means for a male where only 4 cells are affected and what type of life will my baby will expect.
My son was very petite and i am pretty sure my waters broke too early, but they said all was ok. he was very small and about 3 did not grow much.He always used to say he wanted to be a mummy as aposed to being a male or daddy when older. At puberty time he grew little and actually did not start his puberty until 17 and finished by 19. he is well build but 4 foot 9 and has been diagnosed with Brachyolmia. Heterozygous pathogenic variants in PAPSS2: c.809G>,p.(Gly27)Asp):c.1386delGp.(Trp462fs)
and deletion of chromosome 10q11.22q11.23autistic feature, anxiety, acne
Kyphosispaternal history of marfanoid features – no FBn1 mutation identified, but male parent also has deleated chromosome.
Bones break easier, He is always cold and clammy, really wet skin and has wheat and dairy issues.
He did not have a natural suck as a new born.
Joint hypermobility is very bad.
palate slightly arched and prominate ears
we think there is something wrong with his urine , and we need his kidneys checked.
No interest in women . does not have relationships at all.
I was 9 weeks pregnant when they found a severe cystic hygroma on the back of our baby’s neck. They performed a cvs and found that our baby boy had 45xy 46x r(Y) turners. At 14 weeks he had developed severe hydrops and passed. My question is- They say that this is a possible fluke and shouldn’t repeat itself, however are suggesting genetic testing before we have another baby. Is this type of abnormality inherited? Can it repeat in future pregnancies?
Thank you in advance for your response.
Hello; I’m so happy o read you today. My son has 45×0, 46xy (10,40) . He had a severe hypospadias and went through one gonad removal and one orchidopexy for his good functioning teste. My son is a brilliant boy and has no retardation whatsoever. He is very short though and has taken growth hormones for 4 years now . Apparently it works as our endocrinologist says but the progress is slow. I’m worried for his fertility in the future and I’m having a hard time to know where can I find some statistics about adults who tried to procreate with the mosaic condition. Did it worked naturally ? How many of them with a similar number of cells affected ? Would you kknow ? Thank you so much !
When I was pregnant with my son at 18 I had an amniocentesis and found out about my sons diagnosis, I still to this day am confused by all of it, I believe at around six years of age we started seeing an endocrinologist which led to more questions than answers and I stopped going, he is nine now and I’m feeling guilty about not addressing it, he has always seem fine the way he is and I just raise him like any other child, but I have some concerns, he is and always has been so small, and I believe I see signs of thyroid like issues, I want to go back to a different specialist and soon, I’d like to know more about this condition and what I can do to help him in terms of growth. After he was born a genetic doctor told me he would be able to have children but I’m not so sure. If anyone who knows anything about this can email me I would really appreciate it I’m trying to find the paper that explains his diagnosis when he was born. My email is kimwilson2788@aol.com support is hard to find because it seems this is very rare.
Hello,
This is very interesting, I’ve always been told and read that all TS patients are girls. I have a 16 year old girl with TS. She is a lesbian. Any opinions on sexuality within TS patients? Are girls with TS more likely to be lesbians? I also have a 20 year old son who is gay. Just curious on if any studies have been done on TS and sexuality ?
I have turners. Often doctors don’t notice or comment. I am now 73.one doc. Thought my moms mother could have been a pituitary dwarf 4ft10. My father5ft. 6 my mom 5ft7 only male siblings and tley average 5ft6. Was a life long fight for acceptance at employment given to taller applicants.but Axons have it worse
Thank you for sharing! I have a 6 year old son who has 22q delesion syndrome as well and mosaic turners. I have been searching the Internet for the last couple of years trying to fine another male with turners. I would love to chat some time if you are willing? No hard feelings if not?
Thanks so much. You are bringing new awareness to this rare condition and helping to re-educate. The earliest known diagnosis I’ve come across was written about in 1953 but I believe so many boys don’t survive past birth. I’ve become tired of professional and clinical websites brandishing incorrect facts about Turners as I too have a healthy son (aged 9) with Male Turners. We were diagnosed in pregnancy but towards the end, up until then due to his karotype they told us we were having girl and in one of his latter scans they notice genitals! Well that fooled them. He’s our miracle, has few symptoms as yet except very slow growth (and failing to thrive as a baby which we were hospitalised for). There is so little support out there for this rare condition I’m currently struggling as his growth has slowed to almost a complete halt and we are unable to get access to growth hormone treatment due to the UK N.I.C.E guidelines which state he cannot have the treatment because only Female Turners is listed, Male Turner’s isn’t – utter madness. My endrocrinologist believes a trial isn’t possible so we’re stuck due to outdated guidelines. So any thoughts would be gratefully received. Thanks again.
Bonjour, je suis la maman d’un garçon de 18 ans avec Syndrome de Turner en mosaïque 45X/46XY. En France, lorsque mon fils est né en 2001 les médecins ne connaissaient pas le ST chez les garçons… En 2019 certains connaissent mais encore trop peu. Par contre nos fils sont pris à 100% pour tous les soins qui en découlent et aussi pour les hormones de croissance. Mais aucune reconnaissance médicale pour eux en dehors de çà, les médecins continuent à dire que cela n’existe que chez les filles… Ce qui explique qu’il soit aussi difficile d’avoir la moindre information. Aux U.S.A. vous avez aussi l’excellent groupe facebook Male Turner Syndrome (XY) Support Group ou les parents peuvent trouver des tas d’infos et discuter entre eux. Mon fils à eu 2 ans d’hormones de croissance et mesure définitivement 1 m 62 cm. Il est très intelligent et poursuit des études à l’université. Il est en bonne santé. Je suis très touchée par le blog de Lianne Simon, d’une part pour son histoire, d’autre part pour toutes les informations utiles que j’ai pu trouver dedans. Merci Lianne.