What is ADPKD?
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease affecting over 12 million people worldwide. It's estimated that between 1 in every 400 to 2,500 people has the disease. It can affect women and men, across all ethnic groups.
How is ADPKD inherited?
ADPKD is almost always inherited from a parent by a faulty gene being passed to a child. Although we each inherit about 20,000 genes from our parents, only two are linked to ADPKD.
ADPKD is mainly caused by mutations in the PKD1 and PKD2 genes. It has a dominant pattern of inheritance which means that you only need an abnormal gene from one parent to cause ADPKD, even though the matching gene from the other parent is normal. The abnormal gene dominates.
- About 8 in every 10 people with ADPKD have a faulty PKD1 gene.
- About 2 in every 10 people with ADPKD have a faulty PKD2 gene. ADPKD caused by PKD2 is often slower to develop and progress than that caused by PKD1.
ADPKD Inheritance Diagram
The diagram above shows how the faulty (mutated) copies of the PKD1 and PKD2 gene are inherited.
If a person has ADPKD, there is a 1 in 2 (50%) chance they will pass on the ADPKD gene to each child they have. If a child inherits a faulty PKD1 or PKD2 gene, they’ll have ADPKD too.
Each child's risk of inheriting ADPKD is independent of other children. Children who do not inherit the abnormal gene will not develop or pass on the disease.
Not all cases of ADPKD are inherited however. About approximately 5-8% of ADPKD cases are 'de novo' or spontaneous mutations at conception.
How is ADPKD diagnosed?
ADPKD is usually diagnosed by an ultrasound scan. This uses sound waves to make an image of the inside of the body, which can show up cysts in the kidneys.
Genetic tests of a blood sample can be used to look for faults in the PKD1 and PKD2 genes linked to ADPKD. However, genetic testing is uncommon owing to cost and genetic complexity. Rarely, genetic testing is used where diagnosis by imaging is inconclusive or to distinguish ADPKD from other cystic kidney diseases such as ARPKD (autosomal recessive polycystic kidney disease) and some conditions which can 'mimic' ADPKD.
What damage does ADPKD cause to the kidney?
Healthy kidneys are about 10–12 cm long and are found either side of the mid back. They’re filled with about one million special tubes for filtering the blood. These are called nephrons; they filter out waste products and excess water (making urine).
Healthy vs ADPKD Kidney
In people with ADPKD, the lining of individual nephrons can balloon out, causing fluid-filled cysts to form. Over time, more and more cysts appear and increase in size, leaving fewer healthy nephrons and space to filter the blood. People with severe ADPKD can have kidneys as large as a football.
What problems does ADPKD cause?
The first sign of ADPKD is often increased blood pressure, which can begin in childhood. High blood pressure often doesn’t cause any symptoms and is only discovered by a blood pressure test. It’s important to reduce high blood pressure, because it can increase the risk of heart or vascular problems later in life. It can be treated with medication and lifestyle changes.
Common ADPKD-Related Problems
Kidney problems in ADPKD usually occur in adulthood. These can be ongoing, such as a gradual fall in kidney function or discomfort from enlarged kidneys. Other problems occur only periodically, such as infected or burst cysts, a urinary tract infection or kidney stones. Two in three people will experience chronic or acute ADPKD-related pain.
Many kidney complications can be treated, for example with antibiotics and medical procedures. However, it’s not possible to stop the cysts forming. Over time, they eventually take over the kidneys. When the kidneys can only filter about a sixth of the blood that they should per minute, this is called kidney failure (or end-stage renal disease). If your kidneys are failing, you’ll need dialysis or a kidney transplant to survive.
ADPKD can also cause liver cysts, which are known as polycystic liver disease. These cysts don’t usually stop the liver working. However, they can make the liver very large, which can cause pain, discomfort and shortness of breath.
Less commonly, ADPKD can cause other complications. These include a bulging blood vessel in the brain (a brain aneurysm), pockets forming in the wall of the intestines (diverticulitis), or a bulge of intestine or muscle under the skin of the abdomen or groin (a hernia).
What is it like to have ADPKD?
Getting a diagnosis of ADPKD can be a shock. Although people with ADPKD might not get symptoms for many years, the knowledge that they’re likely to become unwell in the future can cause feelings of loss, uncertainty and fear.
People with early ADPKD usually learn to manage the condition well. They’re still able to lead active and full lives, including work, travel and having a family.
As the disease progresses, reduced kidney function can have an impact on daily life. For example, people with poor kidney function need to make changes to their diet. This can limit food options and make eating out tricky.
Those receiving haemodialysis (which uses a machine to filter the blood) need to make trips to a dialysis centre a few times a week. Each dialysis session takes about 4 hours, which is a significant time commitment. Some people can receive haemodialysis overnight at home. Peritoneal dialysis is an alternative to haemodialysis which requires special fluid in the abdomen to be swapped over a few times a day or at night. This can mean taking time out at home or at work.
There may be periods of time when ADPKD affects your life more. For example, you may occasionally get worse pain in your kidney or back. Pain can be especially bad if you have a kidney infection, burst cyst or kidney stone. These complications can make you feel very unwell and you may have to receive treatment in hospital, but usually you will get better after a few days or weeks of treatment.
People with more severe ADPKD often get fatigue. This means they may need to take on less at work and home than they once did.
Does ADPKD shorten your life?
Thanks to advances in healthcare, people with ADPKD are now at reduced risk of some associated life-threatening problems, such as cardiovascular disease.
Although kidney failure is life-threatening, dialysis or a kidney transplant can replace some lost kidney function. These therapies can keep people alive for many years. Despite this, people receiving dialysis or a transplant tend to have a reduced life expectancy compared with the general population.
Is there a cure for ADPKD?
There is currently no cure for ADPKD. In a trial, tolvaptan (a vasopressin V2 receptor antagonist) was shown to help slow ADPKD progression by reducing the rate at which kidneys become enlarged by cysts and helping slow the speed of kidney function decline. Tolvaptan does not alter liver cyst growth. Tolvaptan is licensed in the US, Europe, Canada and Japan. It might not be available in all countries and to all patients.
Potential new treatments are being studied in clinical trials.
PKD International aims to improve the lives of people affected by PKD worldwide, and their families and care-givers. We will do this by uniting patients, families, scientists, and healthcare professionals committed to ending PKD.