Genetic Diagnosis in Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

Leandra is, um, one of our genetic counselors who have been with the fetal Care Center, um, for some time, and her focus is prenatal diagnosis and genetic, uh, abnormality, uh, affecting, you know, the fetuses and as well as in the perinatal period. Uh, Leandra, I will let you take over. Thanks so much. All right. So hopefully everybody can see my slides OK there and can hear me OK, but if not, please do let me know. Um, thanks everyone for joining us this morning to talk about this really interesting topic. And as Doctor Lim mentioned, I'm gonna be taking the 1st 30 or so minutes to talk about genetic diagnosis, um, in fetuses who have congenital anomalies of the kidney and urinary tract. So as I'm sure many of you know, um, there's many different types of examples of congenital anomalies of the kidney and urinary tract, and I certainly don't have time today to go into all of these specific examples and talk about their very specific genetic differential diagnosis. But there's also a lot of different genetic testing options out there, and they can all detect certain things and have their own utility. Um, so today, my goal really is to review with everybody, when you have a fetus who has KIT, when is genetic testing recommended, what genetic testing should be considered, and what are ways that genetic testing can help in the pregnancy, in the neonate, in the pediatric patient, um, and going forward from there. So to start off with some very basic and general guidelines for genetic testing. It can get very confusing and we're gonna get into the details of some of the tests that are out there. So to begin with some very just general guidelines that you can keep in mind, um, babies who have bilateral renal anomalies are More likely to have a genetic diagnosis than babies who have unilateral renal anomalies. And babies with non-isolated anomalies, meaning they have other organ systems affected, are also more likely to have genetic diagnoses than those with isolated renal anomalies. And when looking at all of the babies with cake, it's estimated currently that about 30% of them will have a pathogenic copy number variant or a monogenic disease, and on top another 15 or so% who will have a karyotype abnormality. That's a pretty significant portion of babies with cakiT who will have a genetic etiology. Um, I anticipate that this number is just gonna keep going up. So if you start quoting 30% as your risk of a genetic condition, um, I'm sure we'll be updating that in the near future as more and more genes and genetic conditions are discovered that are linked to CIT. And certainly, depending on the specific type of renal or bladder anomaly, um, the genetic diagnosis, differential diagnosis changes, and it's highest usually the chance of the highest of a genetic condition is highest usually in babies who have, um, cystic kidney disease. So that's, uh, babies who have two or more renal cysts and or increased cortical echogenicity are more likely to have a genetic etiology, with estimates that up to 70% of them may have a genetic condition. And again, when considering the general basics of genetics of the kidney and urinary tract, it is extremely important to remember that genetics is inherently a family business, and family history of cake is very, very common in babies and fetuses who have a congenital anomaly. Um, it's estimated that up to 50% of babies who have KIT will have a family member who also has, um, a congenital anomaly of the kidney or urinary tract, and that's kind of sometimes complicated because it's not always recognized, especially in parents. siblings, if they have a unilateral renal anomaly or something that's very mild, they might not have already been recognized to have that anomaly. And so it is strongly recommended that um renal ultrasounds are performed for first-degree relatives after a fetus is diagnosed with KIP. It's also really important to look beyond the kidney and urinary tract when you're talking about family history. There could be other clues in the family history that could give you a specific direction as far as what genetic conditions to consider. So for example, a baby who has a, um, or a family history of heart defects could be indicative of 22Q deletion syndrome. If there's a family history of hearing loss, particularly sensory neural hearing loss, that could be suggestive of brachiodor renal or BOR syndrome. Um, a family history of diabetes, especially early onset diabetes, could suggest a 17Q deletion, uh, that causes renal cysts and diabetes syndrome. This is certainly not a comprehensive list of everything you might see in a family history, but I hope that it helps illuminate how there are other non-kidney and urinary tract, um, anomalies or health problems that should be considered in these family histories. So I'm sure everybody is wondering or wants to discuss, you know, what are the conditions that we're talking about here. When we're thinking about babies with kidney and urinary tract anomalies, what specific genetic conditions should we be considering? And this is obviously not a comprehensive list, there are. Hundreds of them, um, but there are some general categories that are important to consider. So certainly, as with many babies who have any kind of congenital anomaly, aniploidy, duplications, deletions, and chromosomal etiologies are common. Um, but specifically to cake it, there are a number of monogenic diseases that are important. I know a lot of us often think about the polycystic kidney diseases, autosomal dominant and autosomal recessive polycystic kidney disease, but we should also be considering the nephronathesis disorders and ciliopathies, uh, multiple congenital. Anomaly syndromes, and finally this kind of emerging area incakiT genetics, which is genes that are associated with isolated caki. The list for this gene is just continually growing and growing and growing, um, and I anticipate we're just gonna find out more and more as the years go on. So hopefully that helps to start to answer the question, when is genetic testing recommended? The answer there is, in most babies with CAT, especially bilateral or non-isolated. And now we can move into the question of what genetic testing should we be discussing. And here on this slide, I've shown you an overview of the genetic testing options that are just really generally available in pregnancy, but they all really apply here to CIT Genetics, and we'll go in deeper detail to um all of these options. But first, I wanna put a plug in that it can get overwhelming, it can get confusing. Things don't always present straightforward, genetic, there's so many genetic testing options out there that you might not know where to start. So it's always a good idea to reach out to your friendly genetic counselors, geneticists, and lab representatives. Um, they're here to help. They have lots of good knowledge around these topics and can certainly help you, um, with any questions or to talk through a challenging case. So to start out, I think it makes sense to begin with the consideration about whether all patients are really gonna be interested in diagnostic testing or not. And I think a lot of us know the answer to that is no. Some patients are gonna decline diagnostic testing, and so for those patients, what should we be considering? Um, generally, we should consider different types of parental testing options and self-free DNA screening options, both of which would be non-invasive. When considering parental screening, I kind of think of two general categories in this space. So there's carrier screening, that is certainly appropriate if you suspect a recessive condition in the fetus, typically autosomal recessive, but sometimes X-linked recessive. Um, and ideally you'd have access to sample. from both biological parents from this testing. So for example, you might consider carrier screening in the parents of a fetus who has cystic kidneys and cerebellar anomalies, as these are suggestive of a celiopathy, and you could do carrier screening for the celiopathy conditions. The other broad category is diagnostic testing, but on the parents. So you may suspect a dominant condition in the fetus, and the parent has either suggestive features themselves or has a family history of features, and you would consider testing mom or dad, um, or one of the biological parents, in order to see if you can kind of elucidate what the fetus might also have. So for example, in a fetus who has kidney cysts, and for a parent who has maybe personal history of kidney cysts or a family history, you might consider autosomal dominant PKD testing on that parent, and if you find that variant, it's not diagnostic for the fetus, but you might be able to have a good assumption that that could be what's going on. Just diving into carrier screening a little bit more, um, there are lots of different carrier screening options that are available, especially with expanded carrier screening out there, and this slide is sort of meant to show you that it's a good option, but it's not always a great option. So I compared a very large comprehensive carrier screen that had almost 300 genes on it to a large comprehensive kidney disease panel that has over 300 genes, and they only overlapped by 33 genes. Um, most of Those genes are genes that we would expect to present with pediatric or adult-onset kidney disease, um, and the genes that I would expect could present with congenital anomalies, there was only about 13 of them as they're listed here. So some of the celiopathy genes, um, Uh, multiple congenital anomalies syndrome, Smithloliopits, and some others. So carrier screening is certainly a valid consideration and choice for a family who's not interested in diagnostic testing, but it is really important to keep in mind the limitations of this testing and know that if it comes back negative and the parents are not carriers for the same condition, that does not rule out recessive condition because they're not all tested for, but it also certainly doesn't rule out chromosomal, um, and dominant disorders. The next non-invasive testing option to consider would be cell-free DNA screening. Uh, there are kind of generally three categories of this screening currently available, um, anniploidy screening, microdeletion and duplication screening, and single-gen screening. The annuploidy screening is currently what's broadly accepted by obstetrics and genetics professional societies. Um, whereas the others aren't quite there yet, but they do have their place, um, in consideration. So for the iploidy screening, really the main things, of course, you'd be looking at are trisomies 1318, and 21. Trisomy 18 is most strongly associated with renal anomalies, um, and, and bladder anomalies, but the other ones also have very high associations as well. Uh, the microdeletion and duplication screening could be useful, I think, especially for 2211.2 deletion syndrome, which has a high association with congenital anomalies of the kidney and urinary tract. Um, and there are a few other conditions that may be screened for on these microdeletion panels like 5P deletion syndrome, which is also known as Criduchas. Uh, 1P36 and deletion syndrome and 11Q deletion syndrome, which is known as Jacobson syndrome. These are less commonly associated with renal anomalies or um urinary tract anomalies, but they can be, so they could be potentially helpful. Um, it's also important to remember that they have a low prevalence in the general population, so when you do the math for positive predictive value, there's a higher chance of a false positive for these conditions compared to anyiploidy. And finally, there are some commercially available single gene cell-free DNA screens available, um, and when looking at the genes that are typically available on those, there are a few that can be associated with congenital anomalies of the kidney and urinary tract like CHD 7, which is associated with CHARGE syndrome, or JAG-1, which is associated with alligel syndrome, um, and the others listed here. So similar to carrier screening, um, could be helpful in a patient who is not considering invasive diagnostic testing, but also again, significantly limited in that they're only screening for a small number of conditions. So a negative result really doesn't rule anything out, but also a positive result needs to be confirmed because there is the possibility of a false positive. So moving on from there, we've considered the non-invasive options. So what should we be considering in parents who do want invasive diagnostic testing? Where should our starting point be? And I think in general, for most cases, your starting point will be chromosome level testing either through a karyotype or chromosomal microarray. In some cases, a targeted single gene, um, targeted familial testing or a small panel might actually be the best place to start, um, and we can go into these details in the next slides. But before we get there, um, I'm sure most of you have run into this problem. You have a patient who wants invasive diagnostic testing, but has, uh, anhydramnios related to their kidney or urinary tract anomaly. And so what do you do? You want, how do you get a diagnostic sample? Um, you do have a number of options. So if there is amniotic fluid, that is often but not always the easiest and best option to do diagnostic testing for. If there is no amniotic fluid or it's very low and you won't be able to obtain sufficient sample, um, you might consider sampling the chorionic villi. Uh, sometimes people refer to that as placental biopsy later in gestation instead of just calling it a CVS. Um, you might consider sampling fetal blood through a procedure like a pubs. Um, if there's a lower urinary tract obstruction, you might consider a bladder tap to obtain fetal urine. And if the baby has fluid accumulations elsewhere in the body like a large cystic fibroma, ascites, a pleural effusion, or a large cyst, um, you might be able to obtain fluid from those areas as well. But if there really is no fluid buildup either around the baby or in the baby, something to consider is an amnio infusion where fluid is infused around the baby and then subsequently taken out, um, when it has fetal cells in it to be used for genetic testing. Um, sometimes we also refer to this as an amnio wash. And so going back to one of my first tips in talking about genetic testing, which was reach out to your friendly lab representatives and staff when you have questions. That's exactly what I did here. I reached out to our prenatal cytogenetic techs in our own laboratory and asked them what their experience are with AUwash, what they wish that healthcare providers were obtaining these samples and ordering testing on these samples knew. Um, and their first request was to make sure you really clearly mark the sample type. If it is an amnio wash, an amnio infusion, put that on the tube, put that on the requisition form. They said they can usually tell by the appearance of the sample, but it's important because it changes how they set up the cells in culture, and so if they set it up incorrectly for the sample type, you might further delay your results, so that's really important. Um, the other thing was I always kind of anecdotally thought that we had a much higher failure rate for cell culture on these samples, so I asked them to pull our data, and I was actually surprised to see that by far most of the samples are successful in culture. There was a slightly higher risk compared to amniotic fluid, but it was not nearly as high as what I thought it was. Um, and so usually they're successful. The main difference really is that the culturing can take a lot longer, so you should expect a delayed turnaround time for your genetic tests. Regardless of what the lab's website says about turnaround time, it's probably gonna take longer for these samples cause we have to wait for them to culture, um, and you should counsel your patients accordingly to set their expectations correctly. On a similar note, the reason the cultures take longer is sometimes because there's not enough cells in the sample and they take longer to grow. Um, so for that reason, direct testing methods, which is where DNA is extracted directly from the fluid sample rather than being cultured, are usually not possible on these, um, tests. So again, that further delays the turnaround time. And finally, they mentioned to me that most of the samples they receive tend to either be tinged with maternal blood in the fluid or when they spin them down the cell pellets seem to have red cells in them. Um, so most of the samples seem to be contaminated by maternal blood, so it would be good practice to send maternal blood with all of your amnio wash samples, so that maternal cell contamination studies could be done. So now that you have your sample and you sent it to the lab and you need to order testing, where should you consider starting? Like I said, for most cases, you're gonna want to start at the chromosomal level. Um, it's estimated that about 13% of babies with KKT will have an abnormal karyotype, and that microwave can add about 4% to that diagnostic yield. Most common things we're looking at in the chromosomal space are things like, again, trisomy 1318, and 21, 22Q deletion and duplication syndrome, and 17Q deletion syndrome, which causes uh renal cysts and diabetes syndrome. But there are plenty of publications out there, plenty of case reports, plenty of reviews that talk about lots of other um copy number variants that can be seen in these babies. So this is not a comprehensive list, but these are kind of the big top 5 or 6, syndromes. And then like I said, sometimes you might actually be better off skipping the chromosome testing for the start and starting with either a targeted test, like a single gene, a variant, or a small panel. Certainly, if you have a known variant in the family, um, that's where you should start. This testing again, the cultures take longer, turnaround times are longer, and you have less sample usually to work with, so you should start where you know, and if you know that there's a family variant, that's the best place to start. Um, but otherwise, you might have a, a strong suspicion based on the fetus's presentation and or the family history that you should be looking for autosomal dominant polycystic kidney disease, autosomal recessive polycystic kidney disease, or some other conditions. For example, again, a baby who presents with cystic kidneys and maybe polydactyle and a brain anomaly, you might actually be more concerned about a celiopathy, and it might make sense to start with a small celiopathy targeted panel rather than spending time on the micro at first. Again, this is where your geneticists and genetic counselors can be particularly helpful too, when it comes to interpreting the clinical data. Um, and I wanted to, before we move on from talking about single genes, throw in a couple of statistics about these genes, HNF1B and PAX2. Um, if you're like me, um, when I see a baby who has academic kidneys or cystic kidneys, often the very first thing I think of is autosomal recessive polycystic kidney disease. I order PKD PKHD1 testing, as well as PKD1 and 2 tests. Testing, um, but that actually might be missing a lot of our diagnoses. And so it's estimated that up to 15% of babies, especially with echogenic kidneys and cystic kidneys, could have pathogenic variants in HFF1B or PAXC-2, which is a huge proportion. Um, and so we really would be doing a disservice to patients on the diagnostic odyssey if we weren't looking at these genes. All right. So we've talked about a number of options so far. And I think the last question we might have here at this point is, I've done diagnostic testing. We did the chromosomes, we did the microarray, maybe we did a targeted gene or two, and everything has come back non-diagnostic. What do we do next? And hopefully you're not surprised by this since it's the last thing on the slide, but the next thing to think about would be a broad panel or exome sequencing. These are things that are not targeted to one very specific phenotype, but are really looking broadly at genes involved in the kidney and urinary tract. And when thinking about these panels, I think there's a few kind of reflections that we can have to think about why they can be useful. So first, is it really realistic that you're going to know all of the cakeki genes and all of their features? Remember I said there's hundreds of them, and be able to recognize them and say, hey, we should be testing for this one or 2 genes? Probably not, and I think that's OK. Is it really realistic that a fetus is gonna know the features of those conditions and present in a way that fits nicely in the box of one or two specific genes? Again, probably not. And even moving beyond panels, is it really realistic that the commercially available panels are always going to be up to date and contain all of the genes of interest? Um, usually not. The panels are updated frequently and regularly at labs, but not every day, and so if a new gene is discovered, it's likely it's not going to make it onto a panel for a little while. And even beyond these questions, if you do a micro exome, And we still don't find an answer. Do we expect that that's sufficient and that we've ruled out enough genetic conditions? I'd argue no, and that there's gonna be a space for genome sequencing probably in the very near future, um, regards to these things, the genome sequencing is already rolling out in the pediatric world, and I think it'll come to the prenatal world, not so distant future, so I think we'll be adding that to these slides very soon, um, but I won't be going into detail specifically on genome sequencing, although a lot of the exome-based considerations apply. So when talking about broad panels, what I mean there are, again, panels that are not targeted to cellulopathy or nephrosthesis or A very specific genetic condition, the BOR panel, for example. The broad panels are really looking at a number of genes that are involved in many different types of KCIT, so there's KIT panels out there, or even larger panels that are associated with all types of inherited kidney disorders. Um, these panels can be on the order of a couple 100 genes, and so there really are a broad approach to that testing. Exon sequencing obviously is even broader than that. We're not limiting ourselves to a specific panel. We're doing sequencing of all of the exons in a baby, and then our analysis on the lab side is targeted based on phenotype, inheritance pattern, familial data, all that kind of stuff. Um, and in preparing for this presentation, I pulled some of the larger cohorts of prenatal exome sequencing specifically to see what the yield is for fetuses who present with KIT, and of these, um, 6 papers that I reviewed, there was about a 15% diagnostic yield overall. Um, and similar to what I mentioned at the very beginning, the babies who had non-isolated renal and, um, urinary tract anomalies had higher diagnostic yields than those with isolated anomalies. And exon sequencing is really interesting in many ways because for many reasons, but two that I'll highlight here is that it allows us to have a better understanding of the phenotype of known monogenic disorders. So it's not uncommon that you order a prenatal exome and you get a result back of a known genetic condition that maybe didn't have a strong association with caut before, and your case might be the start of understanding what that prenatal onset renal phenotype could be or severe prenatal onset phenotype could be. Um, it also can help facilitate novel gene discovery again, because we're not limiting ourselves to a specific set of well-known genes. And so to wrap up this conversation about genetic testing, um, I will leave you on a note of caution. You should be aware of the limitations of the genetic tests you're ordering. There is no perfect genetic test. There is no genetic test that can rule out every genetic condition, and there's no genetic test that can diagnose every single type of genetic condition in one test. Maybe one day we'll get there with genome, but um we're not there yet, so it is important to know that whatever you ordered, it has limitations, and you should be aware of what those are. For example, does the test you order report variants of uncertain significance or not? This is particularly important for carrier screening and exome sequencing, since some of the labs who do that testing only report pathogenic and likely pathogenic variants, and so you Might be missing a VUS that's a key to your understanding for a fetus if um you order those tests. They, they certainly have their reasons for doing that, but it's important to know that that's the case so that you know if um you need to request VUSs from the lab, for example. They often will provide those upon request. Um, the other kind of area that I think is important to know about is deletion and duplication, not chromosomal deletions and duplications, but introgenic deletions and duplications, which I think are often forgotten. Um, not all tests evaluate for deletions and duplications, and even those that do are not all made equally. So a chromosomal microarray is really good at seeing copy number variants on a chromosomal level, and it may be able to detect deletions and duplications within a specific gene, but it really depends on the specific microarray you ordered and the specific resolution over that specific gene of interest. So if you have questions about that, reach out to the lab. Um, and even next-gen sequencing panels that market themselves as doing deletion duplication analysis, they do, um, but they're really best for changes that involve 4 or more axons. So a single exon up to 3 axon deletion or duplication may not be detected on those panels, and that's really important for some genes, especially things like H and F1B, where deletions are common. All right, and to wrap up all of this, hopefully to bring it all together before we take your questions, I wanna answer the final question, which is, why does all of this matter? How is genetic testing gonna be helpful? Um, I could probably have spent my entire time on this one slide alone, talking about all the ways that genetic testing can be helpful. We certainly don't have time for that. The point here is that, as you can see, there are numerous opportunities for clinical utility of genetic results, not just positive diagnostic results, but negative results also have their place in clinical utility. Um, and these span from the prenatal period to the neonatal period and beyond. They're informational, they have familial implications, all these are very important. Um, one specific note when considering this is not all of the genes that we know in KIT have um specific genotype phenotype correlations, meaning when you get a genetic diagnosis, it may not allow you to predict the severity of kidney disease that a baby is going to face. But it could give you a guideline as to other non-renal manifestations that you should be looking for. Um, for example, again, a baby with VOR syndrome, you should be doing hearing screening more frequently than a baby who does not have VOR syndrome because sensory neural hearing loss is associated with that. And to bring it all together and show you some of these in practice, I've put together a case example to end this presentation. Um, this isn't a prenatal case, so bear with me, but I think it's a very important case because it can highlight sort of in hindsight, what could have been different had we had an earlier diagnosis. But I think with some of our prenatal cases, we don't know what their outcome is gonna be, and so it can be hard to think forward to that clinical utility. Um, so this was a little girl who presented to the genetics clinic here at 4 years old, um, and she was seeing us because she had a prior genetic diagnosis of ARPKD, but the pathology was not consistent. All over her chart, it said genetic diagnosis of ARPKD, autosomal recessive polycystic kidney disease. But when she had a nephrectomy and they did pathology on the kidney, it was not suggestive of ARPKD. It lacked the classic cystic changes of ARPKD and instead the dominant lesion was um marked pathological changes in the vasculature. So they referred her over to us in our pediatric genetics clinic. Um, a little bit more about her history that we collected. prenatally, everything appeared fine until about 30 weeks when she was noted to have small and echogenic kidneys, and then at 32 weeks developed oligohydramias. In the neonatal period, she spent 2.5 months in the NICU. She was discharged and then the next day she was readmitted to the PICU and stayed there for 2 months. And then, um, she had been started on dialysis at 2 weeks of age and continued on dialysis until she received her renal transplant at 3 years and 10 months of age. Um, until then, she had multiple hospital admissions related to dialysis, blood pressure management, peritonitis, and otherwise she was relatively healthy, happy, developing on track. Her previous genetic test results are listed here, so she had a chromosomal microa that had a result that's normal for a typical female chromosomally female individual. Um, and then she had testing for PKHD1, that's the gene that causes ARPKD that showed a single heterozygous pathogenic variant, so more consistent with carrier status. A second allele, a second variant was not identified on the paternal allele, so she does not have a genetic diagnosis of ARPKD. Um, and she also had testing for the autosomal dominant genes, PKKD1 and PKD2, which identified two variants that were inherited, one from mom and one from dad, um, but they also didn't explain the phenotype. Dad's was just a straight-up variant of uncertain significance. Mom's was a modifier allele that can make the phenotype more severe in people who have other PKD variants, but isn't expected to cause disease on its own. Um, and both mom and dad had pretty large families with a number of siblings, and nobody in the family had any kind of kidney disease. The parents also were interested in this genetic testing and counseling discussion because they were thinking about having another baby and very concerned about recurrence risk, and they had been considering doing preimplantation, genetic diagnosis, and IVF, um, to conceive a baby without any of these variants. So we ordered a broad kidney panel. Lo and behold, we diagnosed a very different condition. So she had a heterozygous variant in the WT1 gene, um, that was pathogenic and had been previously described in multiple people with Denise-Drash syndrome. Denise Drash syndrome is a condition that causes the steroid-resistant nephrotic syndrome that leads to end-stage renal failure, so that explains her clinical course, but it also has a super, super, super high risk for Wilms tumor, up to 90% risk, and the median age of onset of Wilms tumor in these individuals is 15 to 19 months. Thankfully, this patient had already had a bilateral nephrectomy by this time. Um, but certainly had we known about this diagnosis in advance, she would have had aggressive bone tumor screening up until then, and who knows, potentially. Um, I'm not sure, you know, I'm not a nephrologist, not a urologist, but I'm not sure what her kidney management would have been different as far as transplant timing, for example. Um, also, Denise Drash is associated with a 46 XY disorder of sexual development, meaning that individuals with Denise Drash with 46 XY chromosomes can have a spectrum of disorder of sexual development, a difference in sexual development, including having completely normal female-appearing external genitalia. Um, these individuals also have a higher risk for gonadal cancers, so this kind of spurred a moment of anxiety for me because I was worried that we were gonna have to have a conversation with the parents about testing for chromosomal sex to make sure that if she had a risk for these gonadal cancers, that we would be identifying that. And then certainly, you know, if she had 46 XY chromosomes, we all know that chromosomes don't determine your gender. but that can then get into complicated social, emotional, and medical conversations as well. Um, fortunately, then I remembered she already had that microa that had XX chromosomes, so again, this wasn't an issue, but I hope that this sort of illuminates that there were some risks there that we were missing. What if she had developed bones tumor before we knew that this was a concern? What if she had 46? Y chromosomes and at 4 years old, we're having this conversation. What if her parents had done preimplantation genetic testing for those other variants that we know now are not associated with her disease and have wasted all those time and money and all their resources into that testing that wasn't necessary. Um, this is typically a de novo disorder and so we weren't concerned about recurrence risk. Um. So again, I know it's not a prenatal case, but I hope that with some of that clinical course, we can highlight some of the things that could have been done differently had we known of that diagnosis earlier. And with that, um, I thank you all for listening and hope that this is helpful in considering the genetic diagnostic workup for these patients, and I am happy to take any questions that anybody might have. Actually, um, sorry, um, I just saw Alex posted your response. Uh, Alex, instead of, um, just posting that, you want to say what you just, uh, put in a chat box. Sure. Um, to your point, Leandra, as far as a prenatal diagnosis of Dennis Drash, if we've, in, in the past, we've had it both ways where we've had postnatal diagnosis of Dennis Drash, unfortunately, in the setting of the diagnosis of Wilm's tumor. And we've also had Dennis Drash diagnosed um prior to the development of a frank malignancy. And so in those scenarios that you're describing, um, once that baby reaches, you know, pretty, reaches end-stage kidney disease or stage 4 chronic kidney disease and, and dialysis is a renal replacement therapy is impending, um, at the time of peritoneal dialysis catheter placement, we typically will remove both kidneys prophylactically. Because the flip side of it is that, um, the flip side is that if you develop Wilms tumor, and you have to do um bilateral nephrectomies, then the patient has to demonstrate a period of time, usually at least 18 months of oncologic um stability before you can even be considered for transplantation. So there's an inherent delay, um, if you don't, if you have to deal with Wilm's tumor in infancy and then wait. Great, thanks for that. Yeah, so I think that just shows how lucky we got with this little girl. Um, she didn't have her nephrectomies until she was almost 4 years old. Um, so good, that all worked out. The results call the family was like, OK, there's some scary things, but luckily we're past all of that. We don't have to worry about those things. Now, but that could have been a really bad situation that was potentially avoidable had somebody, she had that ARPKD testing like in the neonatal period at a different hospital. Um, if somebody had said like, hey, this doesn't, this doesn't make any sense, we don't have the answer yet, let's order something more. Thanks, Leander, you always do such a beautiful job of providing clarity that it to a topic that in my opinion, has not always very much clarity, so that was wonderful. There was a question from the chat that I know is near and dear to your heart, um, about the topic of whether in Insurance and specifically Medicaid cover um kinds of genetic testing and also if you have an opinion about um which companies provide some of um these good genetic tests. Sure, yeah, um, so insurance. It's complicated. I'm sure you all know cause you're asking the question. Um, typically, the testing would be better covered in the pediatric period, although in my experience, um, It is generally well covered in the prenatal period as well, depending on what you're considering. So microA testing is widely accepted by insurance companies. The only times I've ever had that kind of testing be denied really is people who have insurance policies that just don't cover genetic testing of any kind, which are not common, but they come up. Um, targeted single gene testing is also or small, very small panels like ARPKD or PK, um, ADPKD testing is also generally pretty well covered. It's when you start getting into the broader panels and especially exome sequencing right now that um the insurance. Coverage is different, and there really is no hard and fast rule. I mean, I've had insurance companies who just outright deny those kinds of tests. I've had them who just outright approve them without any second question, and then I've had them where we've had to write letters and do peer to peers and all that kind of thing. So, um. My advice there is don't make any assumptions based on whatever insurance company your patient has listed on their card. There's a lot of nuances to their actual policy, so don't make any assumptions that it's just not gonna be covered, so you're not even gonna try. Do the pre-authorization if they have a commercial insurance. Um, provide letters, provide Your calls, provide references, um, and when possible, really focus on specifics about medical management considerations that you might change. For example, if we've been doing, um, prenatal testing on this baby, if we had been psychic and had a magic 8 ball, we could have said a baby presenting at 32 weeks with oligohydramnia. Small and ecogenic kidneys. We're worried this could be something like Dennis-Drash syndrome, in which case we would recommend a bilateral nephrectomy early in life to prevent the risk of Wilm's tumor. I feel like an insurance company would listen to that kind of, I'm not saying that they definitely will approve it, but that is more compelling than just saying like, because we want to. Um, exome sequencing. It also hit or miss, um, less commonly covered, and hopefully that will change in the future, but I don't know how optimistic I am about the near future, so we'll see on that. Um, the Medicaid question. It is also complicated. So even if Medicaid does cover this kind of testing, a lot of the time they don't reimburse the full amounts. So it really is gonna depend on your hospital's specific policy about balance billing patients who have Medicaid or some hospitals who don't offer um. Institutional billing for their Medicaid patients and it has to be self-pay for some who just can't order this kind of testing on Medicaid patients. It's really hospital-specific, you know, our hospital, we can order the testing and we don't balance bill the patients and so we get all the testing that we want on these Medicaid patients, but like our institution ends up being the one who fits the bill for most of that. That's great Leandra. Thank you again for a rather comprehensive, you know, um, presentation there and um we certainly learned a lot. uh I hope um that did answer some of the important questions for the audience as well.