Congenital Nephrotic Syndrome
Congenital nephrotic syndrome (CNS) is technically defined as nephrotic syndrome that starts in the first three months of life. However, it is often used to describe nephrotic syndrome due to a genetic mutation that starts early in life, so will sometimes be used even if the onset of nephrotic syndrome is slightly later. Although the most common cause of CNS is genetic, occasionally we identify an infection that might contribute to CNS, which would then be treated with the correct antibiotic or antiviral medications.
When a child is found to have nephrotic syndrome at this age, we send off for genetic testing quite early in the investigative process, as there is a good chance that it is a genetic mutation causing CNS. The most common mutations causing CNS are NPHS1, NPHS2, WT1 and PLCE1. The severity of the nephrotic syndrome can be quite varying from child to child, and the treatment that each child receives is tailored to their needs.
As children lose a lot of protein in their urine, they may start to become swollen. Unlike non-genetic forms of nephrotic syndrome, they do not tend to respond to medications that dampen the immune system (like steroids). These might not be used at all, or might be stopped after confirmation from genetic results.
Diet and fluids
Quite frequently a fluid restriction might be required. Losing protein constantly in a baby with a predominantly fluid diet means that some changes might need to be made to their feeds to ensure adequate growth. Dieticians are often involved to advise on growth and feeds. Sometimes, a feeding tube might be required to help ensure good growth. In addition, growth hormone injections might be considered.
Medications
These medications do not cure CNS but can help reduce the protein loss in the kidney, or help to remove excess fluid when required.
- ACE (Angiotensin converting enzyme)-inhibitors e.g. captopril, enalapril and lisinopril
- These are used to try and decrease the amount of protein lost in the urine
- Typically started with some monitoring of blood pressure and blood results as can have an impact on kidney function and amount of potassium in the blood
- Indometacin or other non-steroidal anti-inflammatory (NSAIDs) medications
- Might also be used to decrease amount of protein loss in the urine
- Diuretics e.g. furosemide or amiloride
- These can help to remove excess fluid
It is important to note that if your child is losing fluid and becoming dehydrated e.g. when they have a tummy bug, then they must stop these medications (ACE-inhibitors, NSAIDs and Diuretics).
Albumin infusions
These might be required to reduce the swelling and ensure good growth.
Sometimes a more permanent line like a Hickman line or a Port might be required to deliver the infusions depending on the frequency required. You team will speak to you about this if required. A permanent line is useful if the albumin infusions are frequent, but there is a risk of infection or clotting off.
Clots:
Due to the loss of proteins, there is an increased risk of clots in CNS. Routine anti-clotting medication is seldom given but this might be prescribed when there has been a previous clot, or when there are other factors that increase clotting risk. For example, sometimes an anti-clotting medication or injection is given to help prevent clots from forming around the permanent line.
Infections
Proteins (immunoglobulins) that protect from infections are lost in the urine in CNS. If a bacterial infection is suspected, antibiotics should be started promptly. For patients with recurrent or severe infections, immunoglobulins can be given.
The routine vaccination schedule for children should be followed, and children should receive annual vaccination against influenza. If children are exposed to chickenpox, they should contact their local centre.
Vitamin D
This can be low in CNS due to loss of vitamin D-binding proteins. Levels will be monitored and replaced as required.
Thyroid
Hypothyroidism can occur due to loss of binding-proteins. This will be monitored on blood tests and will be treated if required.
Anaemia:
Iron and other factors (like erythropoietin) important for making red blood cells can be lost in the urine. Iron supplementation is often required. In addition, some children require erythropoietin injections to treat their anaemia.
Removal of kidney
One treatment protocol for CNS is for both kidneys to be removed when the child is about 7-9kg, followed by a period on dialysis and kidney transplantation when the child is 10kg or heavier. Another approach is to keep pursue the above measures (albumin infusions with medications) until this is insufficient, then to remove either one of both kidneys.
Dialysis or transplantation
Children with CNS progress to requiring dialysis or transplantation at different rates, but this is a faster progression than children without a genetic mutation. Your team will talk to you in great detail about this when your child reaches this point, and written information about this can be found on infokid.