Understanding the Two Types of Polycystic Kidney Disease
Approximately 500,000 people in the United States have polycystic kidney disease, or PKD. It’s a form of chronic kidney disease, affecting your kidneys’ ability to filter waste products from your blood as they should. But not all types of polycystic kidney disease are the same. There are two main types: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). So, what’s the difference?
Polycystic kidney disease is generally considered a genetic disorder, meaning it’s inherited from your parents. It causes noncancerous cysts to develop within your kidneys. As a result, your kidneys can increase in size and may eventually lose function. In some cases, these fluid-filled cysts can also grow in other parts of your body, like your liver. When symptoms develop, you may experience pain in your back or side, headaches, enlarged abdomen or feeling of fullness in your abdomen, increased blood pressure, blood in your urine, urinary tract infections, or kidney stones.
Polycystic kidney disease is caused by a mutation in your genes. About 90% of people with PKD will have the autosomal dominant form. With autosomal dominant polycystic kidney disease, you need to inherit just one copy of the mutated gene from one of your parents to develop the condition yourself. If one of your parents has the disease, you have a 50% chance of inheriting it.
Most people with ADPKD don’t experience any symptoms until adulthood around ages 30 to 40, though cysts may start to grow earlier in childhood. If you have a family history of ADPKD and develop any symptoms, imaging studies, such as ultrasound, and genetic testing can be used to make a diagnosis. Complications of ADPKD include brain aneurysms and heart problems, so the earlier you’re diagnosed, the better. This way, you can get started on treatment and undergo any recommended medical screenings. Treatments vary from surgery to medication to lifestyle changes, and about half of people with the disease require a kidney transplant by age 60. However, we’re learning more and more about how to treat this condition effectively, so that statistic may change in the coming years.
Autosomal recessive polycystic kidney disease is much rarer. To be affected by ARPKD, you need two copies of the mutated gene, meaning both of your parents must have a copy of the mutation and pass it to you. Typically, the parents themselves do not have the condition. If both of your parents have one copy of the abnormal gene, you have a 25% chance of getting the disease.
Symptoms of autosomal recessive polycystic kidney disease usually appear early on, often at birth or shortly after. In many cases, ARPKD may even be detected on ultrasound during pregnancy, though it is possible to develop symptoms later in childhood or adulthood. Infants with ARPKD frequently have issues with their lungs, due to lack of amniotic fluid while in the womb and difficulty with lung expansion because of severely enlarged kidneys. Liver problems are often present as well. Around 30 to 50% of newborns with ARPKD won’t survive the first month of life.
Many children with ARPKD will continue to experience problems with their kidneys, often requiring dialysis or a kidney transplant by the time they reach adulthood.
There currently isn’t a cure for either autosomal dominant or autosomal recessive polycystic kidney disease. Recently, a new medication called tolvaptan (Jynarque) was approved by the Food and Drug Administration (FDA) to treat ADPKD in adults with rapidly growing cysts; it helps to slow the growth of these cysts. Other treatments are aimed at controlling symptoms, such as high blood pressure, and preventing complications. But even without a cure, our understanding of polycystic kidney disease continues to grow, improving both life expectancy and quality of life for those living with PKD.