Host:

Polycystic Kidney Disease in children is a rare genetic disease. Cysts are found in the kidneys and liver. Some newborn babies with the disease may die within hours to days.

Today we've invited Hong Kong Children's Hospital, Associate Consultant, Paediatrics and Adolescent Medicine, Dr Ho Tsz-wai to explain it to us.

Hello, Dr Ho. Will you share with us, what's polycystic kidney disease? What type of disease is it actually?

Dr Ho Tsz-wai:

Hello, today we are mainly discussing hereditary recessive polycystic kidney disease. This disease, as the name suggests, is that the patient's kidneys have many cysts. These cysts are what we commonly call "bubbles". These bubbles are filled with liquid. They will replace normal kidney tissues, affecting kidney function.

This disease is caused by PKHD1 gene mutation, on the sixth pair of chromosomes. This mutation will lead to abnormalities in the cilia in kidney cells. They can't make some normal proteins, bubbles are then formed. In addition to the kidneys being affected, the liver will be affected. The bile ducts may be dilated and there may be fibrosis.

Host:

I know that the onset of this disease is critical. About 30% of infants can die within the first few days of birth or even within a few hours. Is it the more serious, the earlier the disease occurs? Why?

Dr Ho Tsz-wai:

The cause of death, I think, is mainly because of the underdeveloped lungs. Let me explain to you why. When a mother undergoes a check-up, that is after the mother becomes pregnant, when doing some structural ultrasound examination, sometimes doctors can already discover that the kidneys of the babies are relatively large in the womb, bigger than the normal baby. And they will be brighter under ultrasound examination.

Then the doctor will also evaluate the baby's amniotic fluid. Because the baby's kidneys are the organs that produce fetal fluid, if its kidney function is impaired, the insufficient fetal fluid will affect lung development. You can imagine if the baby does not have enough amniotic fluid in the womb, there won't be enough space for its hands and feet to develop. This will cause problems with the development of hands and feet. There will be some structural problems.

So, if it is underdeveloped, after the baby is born, it may indeed affect whether they know how to breathe. Poor breathing will require some oxygen or a ventilator to help them breathe.

Host:

Infant in the fetal period may have some problems. Does it mean some early prenatal testing can find out?

Dr Ho Tsz-wai:

Mothers often do now are some noninvasive fetal DNA tests. This particular test is not currently available. But as what I just said, if while an obstetrician or a gynecologist is doing a structural ultrasound and detects abnormalities in the kidneys, there is actually a chance to refer the mother to do more targeted genetic testing. But the risk will be higher. You may need to draw the amniotic fluid or do chorionic villus sampling.

Host:

How about children who develop the disease in the neonatal period? What symptoms do they have?

Dr Ho Tsz-wai:

If after the baby gets through the newborn period, their survival rate is very high, more than 90%. Their kidney function, because there are a lot of bubbles, the kidney function may be affected. There is a chance that the kidney function will gradually decline. It could be in a few years. Your kidney function will gradually deteriorate. Creatinine will rise. There is also a chance of high blood pressure conditions or body salt, that's sodium, will be low.

Host:

For polycystic kidney disease in adults, how is it different from children?

Dr Ho Tsz-wai:

For polycystic kidney disease in adults, the genotype is different. They are a dominant inheritance. Their genetic mutation is not in the sixth pair of chromosomes. And when the illness breaks out, most polycystic kidney disease in adults occur between the age of 30 and 50, and the time to experience renal failure is probably 50 to 60 years old.

Host:

Doctor, you mentioned that the child's liver and kidneys will have problems. Are there any obvious symptoms that parents can notice?

Dr Ho Tsz-wai:

In some cases, for example, a baby with polycystic kidney, the kidney size is larger than normal babies. They may press onto the stomach. So maybe the baby will appear to have loss of appetite. Poor renal function will also cause loss of appetite. Another thing is that they may have a bloated abdomen. So, if these symptoms occur, you can also go to the doctor for a checkup.

Host:

Doctor, do you have any cases you can share with us?

Dr Ho Tsz-wai:

We had a kid, during the mother's pregnancy, whose kidney abnormalities had been found. So, she was taken care of by the renal team from birth. She was lucky to have survived the infant stage. She needed to be on the ventilator for the short term to help her breathe, but she got through. In the first few years, her kidney function was enough to handle the daily function. But at the age of seven, her kidney function was really declining. This led to the need for dialysis treatment. Despite this, she has always been optimistic. She is also a very polite little girl and goes to school like other children, although she has illness. Fortunately, the child received a kidney transplant this year. No more peritoneal dialysis is needed, and she can live a more normal life.

Host:

What treatments are currently available? Before a kidney transplant is possible, do all children need dialysis?

Dr Ho Tsz-wai:

Initially, there is supportive treatment, just try to control your blood pressure. One is a healthy eating habit and another one is a healthy lifestyle to slow down kidneys' decline. In addition, the liver needs to be monitored regularly, see if there are some…for example, high venous pressure. There is a chance of gastric varices or esophageal varices, conditions that cause bleeding. These regular follow-ups can support the children. If eventually they have kidney failure, in the end, they all need a kidney transplant.

Host:

Doctor, can you share with us what is the inheritance pattern of this disease?

Dr Ho Tsz-wai:

This pattern is recessive inheritance. It means each person has 23 pairs of chromosomes in total. Each pair has two. One half of it is inherited from the father, the other half is inherited from the mother. Two chromosomes are required. It takes both chromosomes to have this gene mutation, to have this disease.

Host:

Thank you doctor for sharing with us today. Let's wrap it up here. Goodbye.