Diagnosed with focal segmental glomerulosclerosis (FSGS)? Here's what to know about your treatment options

Focal segmental glomerulosclerosis (FSGS) is a kind of kidney damage that occurs when scar tissue develops in the glomeruli, the dense network of tiny blood vessels that filter waste from the blood.

This pattern of injury — as nephrologist and FSGS researcher Fernando C. Fervenza, M.D., Ph.D., at Mayo Clinic in Rochester, Minnesota, calls it — can be caused by a variety of factors. Whatever the cause, scar tissue in the glomeruli can become more extensive over time.

The term "sclerosis" in glomerulosclerosis refers to the hardening, scarring or thickening of tissue. This makes it harder for the kidneys to do their job. This job of the kidneys involves includes filtering out waste, keeping the delicate balance of the blood's composition and helping to regulate the body's blood pressure, among other tasks. If the glomeruli become too damaged to keep up with the demands of the body, FSGS can lead to kidney failure.

But treatment can help protect your kidneys from damage and functional decline. And for some, it is possible to experience remission. Dr. Fervenza says this is key to preserving kidney function long-term. Below, learn more about the treatment options available for FSGS.

Below, learn more about the treatment options available for FSGS.

There are four types of FSGS — primary, secondary, genetic and unknown. The designations are based on the cause of the kidney damage. To learn more about each type, read Mayo Clinic's guide here.

With primary FSGS, there isn't an underlying disease or condition causing FSGS. Instead, primary FSGS is thought to be caused by circulating molecules that damage and dysregulate certain kidney cells on the surface of the glomeruli. When treating primary FSGS, Dr. Fervenza says the goal is to reduce or eliminate protein in the urine, called proteinuria. This approach is associated with better kidney survival over time.

With secondary FSGS, there is an underlying or secondary cause. Possible underlying causes include drug toxicity and misuse, some chronic conditions and certain infections, such as HIV, hepatitis B, hepatitis C and COVID-19. Typically, treatment is focused on addressing the underlying cause of FSGS, which in turn may prevent or slow down kidney damage, Dr. Fervenza says.

It's especially important to distinguish between primary, secondary and genetic FSGS because it can affect what medicines your care team recommends. People with primary FSGS, for example, may benefit from immunosuppressive medicines. But these same medicines may harm those with secondary FSGS.

With genetic FSGS, certain gene changes that can increase the likelihood of FSGS are passed down from parent to child. Some genetic changes can increase the risk of treatment resistance. In particular, the APOL1 gene variant is associated with treatment resistance and a higher likelihood of kidney failure. It's critical to talk to your care team about genetic testing. This is especially true for Black people diagnosed with FSGS, an estimated 75% of whom have an APOL1 gene.

Finally, with unknown FSGS there is no clear cause of damage to the glomeruli. In these situations, Dr. Fervenza says treatment is mainly focused on managing symptoms, such as high blood pressure, also called hypertension, high cholesterol levels and swelling, called edema, as well as limiting salt and protein intake.

In addition to the type of FSGS, the timing of treatment matters. Dr. Fervenza says the earlier FSGS is diagnosed and treated, the better. Potential signs and symptoms of FGSG include high blood pressure, swelling of the body — especially in the legs, ankles or around the eyes — foamy urine or weight gain. If you've noticed these changes, call your healthcare professional. And if you have already been diagnosed with FSGS, don't ignore changes or worsening symptoms.

The right treatment plan depends on a variety of factors, including the type of FSGS, the extent of scarring to the glomeruli and your symptoms. But often, the goal of treatment is to reduce or eliminate the amount of protein in your urine. Protein in the urine is called proteinuria, and it is often used to determine whether FSGS is in remission, partial remission or relapse. You can learn more about proteinuria, and why it's important,

Your care team may recommend the following treatments:

• Corticosteroids. These medicines work by lowering the body's immune response. Corticosteroids are considered a type of immunosuppressant. In the past, Dr. Fervenza says the standard approach for primary FSGS was high-dose steroids, which came with considerable side effects. Now, there are a range of new treatment options that, for certain people, may be used instead, he says.
• Calcineurin inhibitors (CNI). CNIs are another type of immunosuppressant used to treat primary FSGS. If steroids cause too many side effects, or if you are resistant to steroids treatments, your care team may recommend a CNI. These medicines may be used alone or in combination with a low dose of corticosteroids. Options may include cyclosporine (Gengraf, Neoral, Sandimmune) and tacrolimus (Astagraf XL, Envarsus XR, others).
• Alternative therapies. For those who can't take corticosteroids or CNI medicines, alternative therapies may include mycophenolate mofetil (Cellcept, Myhibbin), rituximab (Riabni, Rituxan, others), obinutuzumab (Gazyva), cyclophosphamide (Cytoxan) or adrenocorticotropic hormone (ACTH), among others. As always, talk with your care team about your options, including effectiveness and potential side effects.
• Blood pressure medicines. Angiotensin-converting enzyme (ACE) inhibitors or angiotensin 2 receptor blockers (ARBs) can help lower blood pressure and reduce the amount of protein in the urine. ACE inhibitors or ARBs may be used alone or in combination with other therapies.
• Cholesterol medicines. Medicines,
  such as statins
  , may be used to help lower cholesterol.
• Diuretics. Edema is a type of swelling caused by salt and fluid retention. It usually affects the legs and ankles. Diuretics can help remove this excess salt and water from the body by increasing sodium excretion in the urine. Lifestyle changes, such as reducing the amount of salt you eat, also will make a difference.

In addition, there are a number of emerging treatment options on the horizon. Spartesen (Filspari) is already used to treat another glomeruli condition and is under consideration from the U.S. Food and Drug Administration (FDA) as a treatment for FSGS. A medicine called inaxaplin is currently being studied for those with the APOL1 gene changes. Dr. Fervenza is particularly optimistic about the antibody therapy obinutuzumab, which may help those who haven't responded to other therapies.