FSGS is a term used to describe the appearance seen on a kidney biopsy. It suggests areas of “scarring” within some of the glomeruli.
There are many causes of FSGS. These include:
- Immune causes: The exact immune mechanism is still unknown.
- Genetic causes: About 50-60 genes have been identified to cause FSGS.
- Other causes: FSGS can occur because of other medical conditions like diabetes, high blood pressure, obesity, infections, autoimmune diseases, single kidneys.
Doctors typically will look for secondary causes first. If these are not present, then FSGS can be due to immune or genetic causes.
Without genetic testing, it can be difficult to distinguish between immune and genetic causes.
Hence, if genetic testing is not performed, doctors will often give a trial of drugs that suppress the immune system. If there is a response, it is presumed the cause is immune. If there is no or suboptimal response, a genetic cause may be suspected.
How can genetic testing help in the treatment of FSGS?
With genetic testing, doctors can be more confident whether the disease is immune or genetic in nature. If this is likely to be an immune cause (genetic testing shows negative result), then they are more confident that potent drugs that suppress the immune system can be helpful. If this is likely to be a genetic cause (genetic testing shows positive result), then they may not offer drugs that suppress the immune system since they are less likely to work.
Immune FSGS has a 30% chance of recurrence after a kidney transplant, while in genetic FSGS, the chance of recurrence is <2%.