Focal segmental glomerulosclerosis (FSGS) is a rare condition that affects your kidneys. In FSGS, tiny “filters” that clean blood inside your kidneys, called glomeruli, become scarred (sclerosis).

“Focal” means that only some of around a million glomeruli inside your kidney are scarred. “Segmental” means that only part of each glomerulus is affected.

Keep reading to learn more about FSGS, including its causes, symptoms, diagnosis, treatment, and prevention strategies.

FSGS occurs when specialized cells inside your glomeruli, called podocytes, become damaged. This damage can occur because of different factors. Based on the cause, doctors classify FSGS into one of the following types:

Primary (idiopathic) FSGS

This is the most common type of FSGS. Doctors diagnose it when they can’t pinpoint what’s causing the damage in your glomeruli.

Some researchers believe that special proteins in your blood, called permeability factors, play a role. These proteins can damage podocytes, which causes glomeruli to leak protein into your urine.

Secondary (adaptive) FSGS

If doctors can pinpoint a distinct cause for FSGS, they consider it secondary FSGS.

Health conditions that increase blood flow to your kidneys may be a cause of secondary FSGS. Elevated blood flow puts excessive stress on your glomeruli because it makes them filtrate more blood. Conditions that can cause FSGS include:

Certain drugs (medication-associated FSGS) and viruses (virus-associated FSGS) may also be the cause.

Genetic (familial) FSGS

Genetic anomalies are a rare cause of FSGS. Doctors may suspect genetic FSGS when several family members have the condition.

Symptoms of genetic FSGS tend to appear during childhood. This can be challenging to treat because many children with genetic FSGS are resistant to typical treatments.

How common is FSGS?

FSGS is rare. Researchers estimate that it affects around 1 to 21 out of a million people. However, these numbers have been steadily growing over the past few decades.

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Symptoms of FSGS relate to the progressive decline of kidney function. At first, they may not be apparent. But as the disease progresses, many people begin to experience a set of symptoms known as nephrotic syndrome.

Nephrotic syndrome

Nephrotic syndrome occurs when damage to your glomeruli causes large amounts of protein to leak into your urine (proteinuria). Doctors usually discover this in a urine protein test.

Other symptoms of nephrotic syndrome include:

As FSGS progresses, it can cause declining kidney function. This can ultimately lead to kidney failure. Symptoms of kidney failure may include:

When to contact a doctor

Be sure to speak with a doctor or healthcare professional if you or your loved one begins to experience symptoms of nephrotic syndrome, especially unusual swelling.

If you’re already receiving treatment for the nephrotic syndrome stage of FSGS, speak with a doctor if:

  • your symptoms don’t improve
  • your symptoms become worse
  • you develop new symptoms

To diagnose FSGS, a doctor will perform a thorough physical exam, ask about your symptoms, and order several specialized tests. Some of the tests include:

Results from these tests may suggest to a doctor that you have FSGS. The only way to confirm a diagnosis of FSGS is through a kidney biopsy. This involves observing one or more samples of your kidney tissue under a microscope.

Although rare, a doctor may also recommend molecular genetic testing to confirm genetic FSGS.

FSGS vs. minimal change disease

Minimal change disease (MCD) is another condition that attacks your glomeruli. It has similar symptoms to FSGS, but it’s more common in children. Symptoms of nephrotic syndrome tend to show up much quicker in MCD than in FSGS.

To distinguish between FSGS and MCD, a doctor will order a kidney biopsy. They’ll then use a microscope to study the biopsy sample.

If you have FSGS, a doctor will be able to see it using a regular microscope. But they can only identify MCD using a very powerful electron microscope.

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Treatment of FSGS aims to slow down or prevent the progression of your disease. If you receive a secondary FSGS diagnosis, a doctor will most likely treat the underlying condition.

Medications used to treat FSGS include:

If FSGS progresses to end stage kidney disease, you may need to have regular dialysis or even a kidney transplant.

The outlook for people with FSGS varies greatly. For some people, symptoms will resolve on their own. Even with symptoms, most people can lead typical lives.

But for some, the effects of this chronic condition can be life threatening. No treatment can repair the damaged glomeruli. Treatment can only slow down or prevent the progression of kidney disease.

Even with treatment, FSGS may still worsen over time, leading to kidney failure. If this occurs, you may need a kidney transplant or dialysis to stay alive. Even with a transplant, there’s a one-in-three chance that FSGS might return, according to a 2020 study.

Be sure to speak with a doctor about your individual outlook.

Living with FSGS

In the words of one person with an FSGS diagnosis, living with this condition can be “scary, difficult, and filled with disbelief, fear, and in some cases, depression.”

But with the help of a qualified nephrologist and a strong support system, many people are able to live a happy life.

In addition to medication, certain lifestyle changes can improve your condition:

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According to 2020 research, FSGS is up to twice as common in people assigned male at birth than in those assigned female at birth.

FSGS is also five times more common in Black people compared with white people. According to 2021 research, this may be because of specific gene variants found only in people with African ancestry. Still, other environmental factors and stressors may also play a role.

FSGS can happen at any age, but it most often occurs in adults 45 years old or older. Experts estimate that around 7% to 10% of children and 20% to 30% of adults with nephrotic syndrome have FSGS.

Many of the risk factors for FSGS are out of your control. Still, you can lower your risk of this condition by:

FSGS is a rare, chronic condition that affects glomeruli in your kidneys. It’s most common in people assigned male at birth, Black people, and those over 45 years old.

In most cases, the cause of FSGS is unknown, but it can sometimes be due to certain underlying conditions. Doctors diagnose FSGS through a kidney biopsy.

No cure exists, but certain medications and lifestyle changes can slow down and even prevent the progression of this condition. With treatment, most people can manage symptoms and lead a typical life.