Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common, life-threatening genetic diseases, affecting 600,000 Americans and 12.5 million people, worldwide.

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ADPKD

ADPKD causes fluid-filled cysts to grow on the kidneys. Over time, these cysts multiply and grow, in 50 percent of cases, causing kidney failure. Dialysis and transplantation are the only treatments for kidney failure. There is no treatment or cure for PKD.

ADPKD affects 1 in 500 newborns, children and adults regardless of sex, age, race or ethnic origin. It does not skip a generation. Parents with ADPKD have a 50 percent chance of passing the disease on to each of their children.

Common symptoms of ADPKD include high blood pressure, pain in the back, side or stomach, blood in the urine, kidney stones, frequent urinary tract infections, a family history of kidney problems, heart problems or strokes. Anyone experiencing one or more of these symptoms should see a doctor.

A cyst in the kidney begins as an outpouching of the nephron, similar to a blister. Cysts can occur anywhere on the length of the nephron. Although polycystic means many cysts, not every nephron forms cysts. The fluid inside the cysts often reflects the area in the nephron from which the cyst arose.

Approximately 70 percent of cysts detach from the nephron when they are still very small, about 2 mm (1/8 inch) in diameter. Over time the cysts enlarge and can become filled with clear fluid or fluid that contains blood or white blood cells.

Cysts can form in other organs as well as the kidney; the most common other site is the liver. Current research suggests that liver cysts are associated with the bile ducts or tubules of the liver rather than liver cells themselves. It appears that rather than take the place of functioning liver cells, cysts merely push the liver cells aside. This is why liver cysts don't cause liver failure even though the liver can become quite enlarged due to cysts.

Research has shown that there are at least three components to cyst formation:

1. Cell proliferation: The cells of a cyst wall reproduce themselves more than do normal kidney cells. This makes the cysts grow in size.
2. Cellular secretion: Secretion is a way of making fluid. To form a cyst the cells themselves must produce fluid. If there were no fluid produced to fill the cyst, there would merely be a ball of cells.
3. Abnormal basement membrane: The basement membrane is a very thin layer of tissue the cyst cells sit on. In ADPKD this layer is thicker than usual and is made up incorrectly.

In general, cysts cause problems because of their size and the space they occupy. The size of the kidneys and liver is directly related to how many and how big the cysts are. For example, people with kidneys over 15 cm (6 inches) are more likely to have pain than people with smaller kidneys.

More info can be found here:
ADPKD Frequently Asked Questions @ PKD Cure

ARPKD

Autosomal recessive polycystic kidney disease, ARPKD, is a rare genetic disorder, occurring in approximately 1 in 20,000 individuals. Parents are carriers of the gene mutation and there is a 25 percent chance in each pregnancy that both copies of the gene will be transmitted to the baby. Roughly 30 percent of all babies with ARPKD will die at birth and about one-third of children with ARPKD who live beyond the newborn period will require dialysis and kidney transplantation by 10 years of age. Small cysts form in both kidneys when a child has ARPKD and they often become quite enlarged. Children with ARPKD also have the liver abnormality called congenital hepatic fibrosis that may lead eventually to enlargement of the liver and spleen. Other symptoms of ARPKD are high blood pressure, frequent urination, anemia, poor growth, varices from the liver complications, and many more.

Learn more about ARPKD @ PKD Cure