Updated on August 20, 2026.
The kidneys are a pair of organs that act as filters for the body. As blood moves through the kidneys, excess fluid, waste, and other unneeded substances are filtered out and become urine. Blood cells, proteins, nutrients, and substances the body still needs are directed back into the bloodstream.
Focal segmental glomerulosclerosis (FSGS) is a type of kidney damage that disrupts this process.
What happens to the kidneys when a person has FSGS?
A healthy kidney contains roughly one million filtering units called glomeruli. These are networks of tiny blood vessels. The walls of these blood vessels allow some substances to pass through (like excess fluid and waste), while keeping other substances in the bloodstream (like blood cells and proteins).
FSGS occurs when there is damage to these blood vessels. Substances that should remain in the blood end up in urine. Excess fluid and waste remain in the blood. Sections of glomeruli become scarred and hardened, reducing overall kidney function.
The different types of FSGS
FSGS is not a single disease but a pattern of damage that can occur for several reasons and circumstances.
- Primary FSGS occurs on its own without any identifiable cause. It may be triggered by an issue with the immune system.
- Secondary FSGS can be caused by coexisting health conditions, chronic viral infections, the use of certain drugs or medications, injury to the kidneys, and/or coexisting kidney diseases.
- Genetic FSGS is caused by genetic mutations that can be inherited or occur on their own.
What complications can FSGS lead to?
FSGS can lead to serious complications, especially when untreated.
High blood pressure
As blood travels through the body, it exerts force against the walls of blood vessels. This force is called blood pressure. When the kidneys do not function normally, excess fluid and other substances (like salts and hormones) cause blood pressure to increase. Kidney damage can cause hypertension, or blood pressure that is chronically elevated. Hypertension can accelerate kidney damage, and also damage the eyes, heart, and brain.
Nephrotic syndrome
This is a cluster of symptoms that occur as a result of proteinuria, or large amounts of protein leaking from the bloodstream into urine. Signs and symptoms include edema (swelling due to fluid buildup, often in the feet/ankles and/or around the eyes), weight gain, foamy urine, fatigue, and loss of appetite.
Complications of nephrotic syndrome can include:
- Blood clots
- Infections (including sepsis)
- High cholesterol and triglyceride levels in the blood
- Coronary artery disease
- Anemia
- Hypertension
- Weakened bones
End-stage renal disease
Chronic kidney disease (CKD) occurs when the kidneys have been damaged for 3 months or longer and are no longer able to fully function. There are different stages of CKD, which are calculated based on the amount of blood being filtered through the kidneys and the amount of protein that is present in the urine.
When the kidneys are functioning at 15 percent or less of the rate of healthy kidneys, a person has kidney failure, or end-stage renal disease (ERSD). This will require treatment with dialysis or a kidney transplant for a person to remain alive. A significant percentage of people with FSGS progress to end-stage renal disease.
Treatment for FSGS
Identifying the type is critical to treatment. Treatment recommendations will vary depending on the type of FSGS, kidney function, and a person’s overall health, but can include:
- Medications to control blood pressure and reduce proteinuria (protein in the urine). Reducing proteinuria is associated with better outcomes and kidney function.
- Steroid medications (glucocorticoids) and immunosuppressive drugs may be used in the treatment of primary FSGS but are potentially harmful to people with other types
- Medications to treat specific symptoms, such as edema (fluid buildup), elevated cholesterol, and blood clot risk.
- Lifestyle interventions, such as limiting sodium and/or protein intake, regular exercise, quitting smoking (for anyone who smokes), avoiding alcohol, and taking certain vitamins. Changes to diet and exercise habits should always be made under the guidance of a healthcare provider.
- Novel therapies and/or clinical trials. New therapies for FSGS are actively being researched and developed.
Your best source of information regarding FSGS diagnosis and treatment will always be a healthcare provider. People with FSGS should work with a nephrologist with experience in treating rare kidney diseases.
