Most cases of autosomal dominant polycystic kidney disease (ADPKD) are caused by either one of two genetic mutations – PKD1 and PKD2.
A genetic mutation occurs when the instructions that are carried in certain genes become ‘scrambled’. This means that some of the body’s processes do not work normally.
The mutated PKD1 and 2 genes are found in all of the kidneys cells. In a small number of cells, the mutated genes cause the cells to reproduce abnormally, which causes cysts (fluid-filled sacs) to form.
The fact that PKD1 and 2 genes are found in all of the kidney cells. But only a small percentage of these cells are affected by cysts, so experts argue that some sort of second trigger or ‘second hit’ is needed to stimulate the abnormal growth in the affected cells.
The general consensus is that the second trigger is probably an additional genetic mutation that occurs some time after birth.
Non-inherited ADPKD
In around 1 in 4 cases of ADPKD, a person develops the condition without having a family history of the condition. In some cases, this is could be because the condition was never diagnosed correctly in a relative, or a relative with the condition may have died before their symptoms began.
However, it estimated that in 1 in 20 of all cases of ADPKD, the gene mutated ‘by itself’ even though neither parent of the person affected has the condition. This is called spontaneous mutation. It is not known what causes the genes to mutate.
Once a gene has become faulty, the person who is affected can pass the faulty gene on to their children.
Autosomal dominant mutation
All of the genes in your body come in pairs. You receive one half of the pair from your mother and the other half from your father.
The mutation that causes ADPKD is an autosomal dominant mutation, which means that only one half of the gene pair needs to be affected by the mutation in order for the condition to arise.
This means that if either one of your parents has ADPKD you have a 1 in 2 chance of developing the condition yourself.
Similarly, if you have ADPKD, your children will have a 1 in 2 chance of developing the condition themselves. This is because:
- there is a 50% chance that they will get a normal gene from you and a normal gene from your partner and not develop ADPKD
- there is a 50% chance that they will get the normal gene from your partner and a mutated gene from you and develop ADPKD
