In polycystic kidney disease (PKD), cysts grow inside a persons kidneys, in most cases leading to kidney failure. A healthy kidney filters out toxins in the blood and eliminates them from the body in the form of urine. In autosomal dominant polycystic kidney disease (ADPKD), there are at least two genes, which, if mutated, can cause cysts to grow in the kidneys. These genes are PKD1 on chromosome 16 and PKD2 on chromosome 4. In autosomal dominant polycystic kidney disease (ADPKD), there are at least two genes, which, if mutated, can cause cysts to grow in the kidneys. These genes are PKD1 on chromosome 16 and PKD2 on chromosome 4. Everyone has two copies of both the PKD1 and PKD2 genes; one PKD1 and one PKD2 gene is inherited from each parent. A person with a mutation in one of the PKD1 or PKD2 genes will eventually develop polycystic kidney disease. There are no directly adverse consequences of having only one working copy of PKD1 or PKD2. However, over the years, there is a fairly high probability of "spontaneous" mutations in the working copies of PKD1 or PKD2. For a person who inherited a mutation in PKD1 or PKD2, every kidney cell has that mutation. Over the years, some fraction of the kidney cells may acquire a mutation in the other copy of the gene. Kidney cells with two mutated copies of the PKD1 or PKD2 genes will develop into cysts. Why are PKD1 and PKD2 so important? The cell uses these genes to produce two proteins, polycystin-1 and polycystin-2. Together, polycystin-1 and polycystin-2 form a channel on the surface of the cell, which allows small molecules to enter. These molecules "identify" the cell as a kidney cell and trigger the production of kidney structures. If polycystin-1 or polycystin-2 don't work, the cell does not get the signals that identify it as a kidney cell. No kidney structures are made. These undetermined cells do not have any blood-filtering abilities and grow into cysts in the kidneys. As the cysts grow, their size can also block the ability of neighboring kidney cells from filtering blood. Eventually, the entire kidney may fail, at which point the patient will require dialysis and a kidney transplant. A person who has a family history of polycystic kidney disease or who has cysts in the liver is at risk for having polycystic kidney disease. A doctor may be able to diagnose PKD by sight or touch. Large cysts in the kidneys can cause the abdomen to bulge. To confirm the diagnosis, the doctor will use some type of imaging technology to detect the cysts. Ultrasound is the most commonly used technology. An ultrasound machine uses the principle of echolocation to see inside the body. Sound waves radiate from the ultrasound probe and penetrate into the body. If they hit dense tissue, they are more likely to bounce back. The ultrasound probe is connected to a computer that calculates the distance the sound waves traveled before bouncing back. The number of waves that came back after a specific amount of time tells the computer how dense the tissue is at that distance into the body. The densities and distances are used to draw a picture. Ultrasound is the best way of diagnosing polycystic kidney disease if the cysts have already begun to grow. Genetic tests are sometimes used to identify PKD before cysts appear, but these tests are usually family-specific and can be expensive. Autosomal dominant polycystic kidney disease (ADPKD) is a dominant genetic disorder. That means you only need to inherit one mutation in one of the PKD genes to develop PKD. When each parent produces sperm or eggs, only one of their two PKD1 genes goes into each cell. In this case, the father has a mutated PKD gene; half of his sperm will have the mutated PKD gene. The child will inherit one copy of the PKD gene from the father and one from the mother. In this case, the child inherited the mutant PKD gene. He will develop autosomal dominant polycystic kidney disease just like his father. Autosomal dominant polycystic kidney disease can also occur as the result of a spontaneous mutation. If neither parent had the disease, but a PKD gene was mutated in the sperm or egg, you can still have the disease (about 10% of cases fall into this category). This child has one mutant copy of the PKD1 gene. He has autosomal dominant polycystic kidney disease. If you have autosomal dominant polycystic kidney disease (ADPKD) and your partner does not, each of your children has a 50% chance of having the desease. To see why, we first represent the parental genes with letters: big P represents the normal PKD1 gene, little p represents the mutant PKD1 gene. If you have autosomal dominant polycystic kidney disease (ADPKD) and your partner does not, each of your children has a 50% chance of having the desease. To see why, we first represent the parental genes with letters: big P represents the normal PKD1 gene, little p represents the mutant PKD1 gene. Again, we can count the squares to determine the probability of different outcomes if these parents have a child. There is still a 50% chance that each child will have polycystic kidney disease. However, there is an additional 25% chance of miscarriage. The most important thing to remember about these odds is that they apply to every child this couple has. It may be useful to think of the Punnett square as a roulette wheel. Each child is a separate "spin of the wheel", so each child has a 50% chance of having polycystic kidney disease. If you have autosomal recessive polycystic kidney disease (ARPKD) and your partner does not, your children cannot have the disease. To see why, we first represent the parental genes with letters: big P represents the normal ARPKD gene, little p represents the mutant ARPKD gene. Each parent donates one of their ARPKD genes to the child, so we place one of the father's genes and one of the mother's genes in each box. Each completed box shows a different possible combination of genes (a genotype) for the child, and the entire square shows all possible combinations. If you have autosomal recessive polycystic kidney disease and your partner is a carrier, your children have a 50% chance of having the disease. To see why, we will draw up a new square, with a Pp mother and a pp father. There are two basic forms of the disease: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). Both have generally the same clinical symptoms, but different underlying genetic causes. ADPKD is dominant; a person needs only inherit one copy of the mutated gene to develop the disease. ARPKD is recessive; a person needs to inherit two copies of the mutated gene, one from each parent, in order to develop the disease. People with polycystic kidney disease have multiple cysts in their kidneys. These cysts invariably increase the size of the kidneys squeezing on surrounding blood vessels. This often causes high blood pressure and impairs the kidney's ability to remove harmful toxins from the bloodstream. In a majority of cases, the kidneys fail. Cysts often appear in other parts of the body: liver, pancreas, seminal vesicles and ovaries. In many cases, the disease causes one of two forms of heart disease (left ventricular hypertrophy and mitral valve prolapse), intracranial aneurysms, abdominal hernias, and other less common symptom. Autosomal dominant polycystic kidney disease (ADPKD) has an incidence rate in the United States of 1 in 500 to 1 in 1,000. ADPKD is generally asymptomatic until the second or third decade of life. Autosomal recessive polycystic kidney disease (ARPKD) is less common, with an incidence rate of approximately 1 in 10,000. ARPKD affects infants, either in utero or in the neonatal stage and has a high rate of mortality. Polycystic kidney disease causes large cysts to grow in an affected person's kidneys. Ultrasound and other imaging technologies can be used to see the cysts and diagnose the disease. A genetic test may also be used in a family with a history of the disease. Autosomal dominant polycystic kidney disease (ADPKD) is caused by a mutation in one of two genes: PKD1, PKD2. Proteins encoded by these genes seem to work together as a signaling system for kidney cells. When this signaling system breaks down, the cells no longer develop into the correct kidney structures, and instead form amorphous cysts. There is currently no cure for polycystic kidney disease. In the early stages, a patient can be treated for high blood pressure, pain, and any other secondary symptoms. If the disease progresses to the point of kidney failure, dialysis and kidney transplantation provide replacement therapy, but does not cure PKD. Facts and theories symptoms treatment cause testing and screening incidenceA healthy kidney works just like a filter blood full of toxins is pumped into the kidney, the toxins are sent to the bladder, and then clean blood is pumped back out. When the kidneys fail, as can happen for people with polycystic kidney disease, toxins are no longer cleared from the blood. Dialysis works like an artificial kidney to filter toxins out of the blood. The first type of dialysis to be developed was hemodialysis. Blood is pumped out of the body into a machine, which filters the blood. The blood is then pumped back into the body. The part of the dialysis machine that does all of the work is called the dialyzer. Both blood and dialysate flow through this tube, separated by a thin membrane. Dialysate is a liquid that mimics blood. It has the same chemicals as clean blood, but without any blood cells. To see how the filtration works, well zoom in even further, to see the individual molecules in the blood and the dialysate. The membrane that separates the blood from the dialysate is semi-permeable. Small molecules like salts and toxins can move through the membrane easily, but the blood cells cannot. If any of the small molecules are at a higher concentration on one side of the membrane than on the other, they will cross the membrane. The levels of toxin will gradually become equal on both sides of the membrane, decreasing the amount of toxin in the blood, and increasing the amount of toxin in the dialysate. Then the dialysate is changed, and the process happens again. This is repeated until there are no more toxins, and then the blood is pumped back into the body. Hemodialysis, where dirty blood is pumped out, and clean blood pumped back in, is only one type of dialysis. Peritoneal dialysis is an alternative type of dialysis where blood never leaves the body. Instead, the abdominal cavity is used as a dialyzer. Hemodialysis, where dirty blood is pumped out, and clean blood pumped back in, is only one type of dialysis. Peritoneal dialysis is an alternative type of dialysis where blood never leaves the body. Instead, the abdominal cavity is used as a dialyzer. Dialysate is pumped into the abdominal cavity using a permanent catheter. The peritoneum is a semi-permeable membrane that lines the abdominal cavity. It is laced with tiny blood vessels. Toxins can easily pass through the peritoneum and enter the dialysate. The toxins continue to enter the dialysate until the concentration of toxins in the dialysate is equal to the concentration of toxins in the bloodstream. The dialysate fluid is then discarded, and new clean dialysate fluid is added. Again, the toxins move across the membrane until the concentration of toxin in the dialysate is equal to the concentration of toxin in the bloodstream. This process is repeated until the blood is clean. Hemodialysis and Peritoneal dialysis are both methods for filtering toxins out of the bloodstream without a kidney. Kidney transplantation is another method of replacing lost kidney function. One way to replace lost kidney function is to add a new kidney. Often the original kidneys are not removed, but a third one is added, either from a cadaver or a family member. This new kidney can take over the function of the original kidneys. Unfortunately, the transplant may not last. The body is adept at fighting off foreign invasion, and since the transplanted kidney is foreign tissue, it may be rejected by the immune system. To prevent this from happening, it is important to look for a very close match of kidney donor to patient. What does that mean? Every cell in the body is coated with specific "histocompatibility" or HLA proteins. The immune system recognizes these proteins, and uses them to identify "self." If a cell has the right set of HLA proteins, it belongs. If it does not, the immune system will remove it. There are so many different HLA proteins, and so many different combinations, that only identical twins are expected to match perfectly. However, the patient can take immune suppressant drugs. These drugs "blindfold" the immune system, making rejection of the transplanted kidney less likely. There are so many different HLA proteins, and so many different combinations, that only identical twins are expected to match perfectly. However, the patient can take immune suppressant drugs. These drugs "blindfold" the immune system, making rejection less likely. Immune suppressant drugs are strong enough that even a poorly matched kidney will probably last over a year. Unfortunately, other health-related problems may result due to a suppressed immune system. Kidney transplantation and dialysis are both ways of restoring lost kidney functions to PKD patients with kidney failure. Diagnosis Melissa explains how she found out she has PKD. Developing Symptoms Melissa describes the uncertainty of when and how her PKD symptoms will appear. Diet Awareness Melissa talks about her thoughts on her eating habits as a result of her PKD diagnosis. Dialysis Conflicts Melissa explains the different types of dialysis and how it complicates ones schedule. Transplants Melissa explains the risks of having an organ transplant. Changing Lifestyles Melissa describes how her mothers life has changed since her diagnosis. Finding Support Melissa describes different sources of support and how they have helped her.
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