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Ambiguous Genitalia Wiki, causes and picturesAug 07, 2011 > Various
Ambiguous Genitalia Wiki and picturesStarting with chromosomal sex, since thatís the thing we often think about first when we see a baby who has ambiguous genitalia. Let me tell you, the chromosomes wonít tell you everything. They arenít always perfect predictors of what the sex of the child is. I think one obvious example is that a karyotype only sees big changes. You might not see the missing piece that will turn an XY person into a perfectly normal looking female. You may not see extra pieces that will turn an XX person into a very normal looking male. What about the concept that if some of the cells are one type - say 45 X - and the other types are 46 XY, what actually happens. And thatís an important concept of mosaicism. Iím not sure they will ask you this on the Boards but in real life you have to remember that you can get mixes of chromosomes, and perhaps that explains some of the cases that we see that are very, very much in between. Now we do a lot of focusing on the gonadal sex. That is, is it an ovary or a testes? But guess what? Itís not always clear. While it normally follows the rules that if you have a Y chromosome you get a testes. Sometimes you do get a little of both. It may have ovarian and testicular tissue in the same gonad. You can imagine how that confuses issues. Sometimes the gonad is missing. It either never developed in the first place or else it was there and then it disappeared. Sometimes it just doesnít make the hormones it is expected to, even though itís there.
Now the third thing - and I think this is very important for diagnostic purposes - are the internal genital ducts, the tubing as you would have it. I donít know, maybe you have your mnemonic. I just remember that M stands for mother and W stands for wolf-whistle, to remember which ones are the "female" and which ones are the "male" structures. But really the thing that I think is important is that there are two mullerian structures that are diagnostically very very important, and I put them in orange. And one of them is the uterus. If you see a uterus on the ultrasound, there was something there that a male normally makes that wasnít made. If you see the upper two-thirds of the vagina is there, you know that that male factor wasnít active, that keeps that from being made. So itís very important because these are structures you can see on ultrasound, in the case of the uterus, or on your physical exam, if you do a pelvic exam.
Ambiguous Genitalia CausesNow the thing that we see in the delivery room, the thing that I think really leads to a lot of the distress, is the external genitalia, the ambiguity of the external genitalia. The rule is - and this is what an examiner might try to ask a question, to see if you understand - is that for every female genital structure there is a male equivalent, and vice-versa. So the clitoris is the analog of the penis. On the other hand, sometimes you have something and you donít know whether itís a large clitoris or a small penis. There are also other analogs as well. The labia minora in a male would form a tube around the urethra and recall the corpus spongiosum. The labia majora would fuse in a male to become a scrotum. And the lower third of the vagina is a prostatic utricle. Thatís not as useful, but these other things are very very important to know. And in between you can get things like hypospadias, or you can get posterior fusion and you donít know if itís fused labia majora or actually a partially fused scrotum. Just the idea that all these things can be in between - and Iíll show you some clinical examples in just a little bit. Now there is obviously the idea of do you have estrogens or androgens in your system? And does your body respond? Iíll show you an example of when the body doesnít respond to androgens, you get a female outcome. What they call the androgen insensitivity syndrome.
There is also the psychosocial aspect and I wonít get into that now, but from a management point of view, this is very important; that whatever decision you finally make on a sex assignment case, that the family, the physicians, everybody is firmly on that same wave length.
So really the key concept, number two -which is just a corollary of concept number one - is that many of these different levels may be discordant. They donít always follow together. For example, if you have a question that asks, "Here is somebody with a uterus, do they definitely have a 46 XX karyotype?" I think you probably know the answer. Definitely no, they may not. Hereís another classic example. Somebody has well developed breasts, normal female genitalia, 100% female identity, does this automatically guarantee they have a 46 XX karyotype? Again, not necessarily. If they have primary amenorrhea, a blind short vagina, and no axillary or pubic hair, they may very well be 46 XY but they didnít respond to testosterone. In many cases this is the classic example of androgen insensitivity. Where somebody who looks like this turns out to have a hernia with a testes in place.
An important key concept, pathophysiologically, is that the default pathway for sexual differentiation is female. So that if you donít have any ovaries - if you have a fetus who has no gonads whatsoever - the default pathway will be female duct and genital development. On the other hand, the testes has to be there to suppress those mullerian ducts, those female ducts like the uterus and upper part of the vagina, and two, to stimulate the development of male genitals. So to make a male you have to have the right chromosomal signal, usually on the Y chromosome. You have to have two signals from the testes; one, the mullerian inhibiting substance to inhibit the female ducts, and two, testosterone to stimulate the male genitalia formation. You need to be able to convert testosterone one final step to dihydrotestosterone that finishes off the genital development, and you do also need pituitary signals to insure that the penis is full length, for example.
There is an important concept medically, that there is a critical period for external genitalia development and this is week 8-12. After the second month. Before that the male and female genitalia in the fetus look exactly alike. Between 8 and 12 weeks any androgen - whether itís something the mother took, whether itís a tumor the mother has, or whether itís an adrenal problem that gives the mother too much testosterone - will lead to full virilization, where if you had somebody who was a 46 XX female and was exposed to a lot of androgen in this critical period, they would end up looking quite male. After 12 weeks, the fetus is no longer quite as sensitive and while youíll get some virilization, you wonít get the extreme ambiguity you would at the earlier period.
You need to know what are some of the signs of virilization. Clitoromegaly is one. But I will tell you that there are standards, but itís very hard to measure a clitoris and itís sort of like the Supreme Court definition of pornography, "you know when you see it." Now I want to warn you that the clitoris of a premature infant can look very prominent because there isnít a lot of labial fat on the sides, so it looks like the clitoris is sticking out there. But I think most of us would realize that this is not clitoromegaly. But once in a while we get some calls because someone thinks the clitoris looks very prominent. Another thing that you have to be careful of; this is a normal female infant. Her labia minora are very stimulated, perhaps because of her motherís hormones, and this will go down as the infant grows up. This is not clitoromegaly. These are just very stimulated, estrogen-stimulated labia minora.
Another thing that is important is that if you see a migration of the urethral opening to the shaft of what would be the clitoris - and the urethral opening in a male should be at the tip of the corona, and in a female is down at the base of the phallic structure, but it could be anywhere in between depending on how much androgen the person has. Another very important feature for virilization is any kind of posterior fusion at the labia. One thing you can look at is see where the fusion is, or see where the posterior part of the vaginal opening, and see if itís closer to the base of the clitoris than it is to the anus. If it is, thatís a sign of significant posterior fusion and maybe a sign of virilization in a female.
You have to know the converse too. What does an under-virilized male look like? Obviously a small penis is one thing, and you can remember the one inch rule as a rule of thumb for a term newborn. A penis that is less than one inch in length is more than 2 Ĺ standard deviations below the mean. That should be easy to remember, hopefully. Obviously hypospadias can be a sign of under-virilization, although it may happen sporadically with no hormone problems. And another thing thatís come up - actually very recently we had a case - where a child may have a bifid scrotum. Iíll show you a picture of each of these in a second. I donít think any of us need to be told that this is a micropenis. You do need to push the suprapubic fat pad back to make sure that you are getting the full length of the penis, and you do need to measure the stretched penile length. Not just look at it and try to estimate. The hypospadias, or mild hypospadias, may be a sign of under-virilization. Certainly if the urethra is down here near the base of the penis, thatís a very distinct sign of under-virilization and should increase your level of suspicion for an androgen disorder.
Here is an example Ö this is a bifid scrotum where you actually have some fusion in the midline right here, and that can be a sign of under-virilization as well.
Now any exposure to excess androgens during that critical 8-12 week period will lead to virilization and the most common thing that you will run into, and have a very good chance of running into - particularly if you deal with a Hispanic population or you live in New York City - and that would be virilizing CAH, or congenital adrenal hyperplasia. And you should know this entity relatively well. Iíll cover that in a second. Obviously if mother had an androgen-excreting tumor and she herself was virilized, or if she were taking any androgenic meds, that would be a smoking gun as well. But much less common in our practice.
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