Understanding and Treating the Four Types of FSGS

In the United States, an estimated 37 million adults—about 1 in 10—are living with chronic kidney disease, yet nearly 90% don’t know they have it. Focal Segmental Glomerulosclerosis (FSGS), a rare form of kidney disease, affects people of African, Latin American, and Caribbean descent at a higher rate. It can impact both children and adults. FSGS can have serious consequences if left untreated.  

What is FSGS? 

FSGS occurs when scarring develops in the kidney’s tiny filtering units, called glomeruli. These filters help remove waste and extra fluid from the blood. When they become damaged, the kidneys can’t do their job effectively.  

The scarring only takes place in small sections of each filter, and only a limited number of glomeruli are damaged at first. Many people don’t notice symptoms, but when signs do appear, they may include swelling in the legs or around the eyes, weight gain from fluid buildup, and foamy urine—a sign of excess protein. Some people also develop high cholesterol or low protein levels in the blood.  

For some people, FSGS can also lead to a condition known as nephrotic syndrome—a group of symptoms that occur together and signal significant kidney dysfunction. In more advanced stages, symptoms may resemble kidney failure, including fatigue, nausea, shortness of breath, itching, and loss of appetite. 

Who is at Risk? 

This condition affects both children and adults and can occur in people of all backgrounds; However, certain groups face a higher risk. Research shows that FSGS is more common among people with African ancestry, as well as those with a family history of kidney disease, obesity, low birth weight, or certain viral infections like HIV. 

Black Americans in particular account for 32% of all kidney failure in the US, and a big factor is variations in a gene called APOL1. 

The APOL1 gene makes a protein in your immune system that helps the cells and tissues fight infection. It evolved over centuries in people who lived in Western and Central Africa through mutations associated with protection against a parasite that causes sleeping sickness, but some variants can also raise the risk of kidney disease. 

We are all born with two copies of the APOL1 gene, one from each parent. There may be a mutation in one or both genes. Thise who inherit genes with two mutations have a 10x risk of developing kidney disease, including a rapidly progressed FSGS.  

Types of FSGS 

Doctors classify FSGS into four main types:  

Primary FSGS happens without a clear or known cause. It may be immune-mediated, which means the immune system attacks and damages podocytes (the cells that filter waste from the blood in the kidneys). 

Secondary FSGS happens because of another health condition or outside factor, such as: 

• How your kidneys are formed at birth 

• Certain medicines, like non-steroidal anti-inflammatory drugs (NSAIDs), lithium, anti-cancer drugs, interferon, or bisphosphonates for bone health 

• Viral infections like human immunodeficiency viruses (HIV), Cytomegalovirus (CMV), Parvovirus, or COVID-19 

• Use of recreational drugs, like heroin and anabolic steroids 

• Obesity (can increase stress on the filters of the kidneys) 

Genetic FSGS is caused by mutations in podocyte or glomerular basement membrane. that can be passed down through families. There are more than 50 genes known to cause these familiar mutations. APOL risk variants, which largely impact communities of Black, African, Caribbean and Latin descent are linked to an increased risk for FSGS. 

Unknown FSGS is classified after extensive testing. The criteria for primary FSGS are not met, and no genetic or secondary disease causes have been identified.  

Treatment Options for FSGS 

FSGS is typically identified through blood and urine tests, but a kidney biopsy is needed to confirm the diagnosis. Treatment varies from person to person but often focuses on reducing kidney stress and slowing disease progression. This may include medications to control the immune system, manage blood pressure, and reduce fluid buildup, along with dietary changes like lowering salt intake. 

Among these FSGS treatments are: 

• Corticosteroids (often called “steroids”) 

• Immunosuppressive drugs 

• ACE inhibitors and ARBs 

In more serious cases, your physician may also recommend therapeutic plasma exchange, also known as plasmapheresis. This process removes and replaces a patient’s blood plasma or the fluid content of the blood through a catheter or needle and circulating it through a machine where plasma is discarded and replaced with a substitution fluid (mainly albumin solution). The substitute plasma and the patient’s blood cells are then returned through another catheter. 

A notable recent development is also offering hope. In April 2026, the U.S. Food and Drug Administration approved a new indication of a medication called Filspari (sparsentan) for reducing protein levels in the urine in patients aged eight and older with FSGS who don’t experience nephrotic syndrome. This marks an important milestone, as it represents the first FDA-approved treatment specifically indicated for this condition. By targeting pathways involved in kidney damage, the drug may help slow disease progression and improve outcomes for patients who previously had limited options. 

Even with new treatments, early detection remains one of the most powerful tools. Simple blood and urine tests can provide important clues about kidney health long before symptoms develop. For individuals with risk factors—such as a family history of kidney disease, high blood pressure, or certain genetic backgrounds—regular screening can make a meaningful difference. 

FSGS may be rare, but its impact is real, especially when it goes unrecognized. By increasing awareness, encouraging routine testing, and supporting ongoing research, the medical community can move toward more equitable and effective care for people of all backgrounds. 

Resources 

FDA Approves Indication for Filspari 

Kidney Disease Improving Global Outcomes: Types of FSGS  

CDC: Types of Chronic Kidney Disease:  

Nephcure: Do You Have Focal Segmental Glomerulosclerosis (FSGS)