Focal segmental glomerulosclerosis (FSGS) refers to scarring (sclerosis) of the glomeruli – blood vessels in the kidneys that filter wastes and excess fluids from the blood. The condition occurs in children and adults and is due to diverse causes. FSGS can lead to decline in kidney function and progression to end-stage kidney disease (ESKD), also known as kidney failure.
The name of the condition can be broken down like this:
[Focal] Some [segmental] sections [glomerulo] of the kidneys’ filters [sclerosis] are scarred.
FSGS Symptoms, Diagnosis & Progression
FSGS damages cells in the glomeruli called podocytes. In a healthy environment, podocytes are a critical part of the barrier between blood vessels and urine, restricting large molecules like proteins from filtering through into the urine. Damage to the podocytes makes this barrier permeable causing proteins to leak into the urine (proteinuria or albuminuria). Proteinuria can make urine appear foamy.
FSGS can also cause swelling (edema), especially in the hands, feet, abdomen and around the eyes; and low levels of protein in the blood (hypoalbuminemia). The condition can also cause high blood pressure and high cholesterol. A definitive diagnosis typically requires blood and urine tests and a kidney biopsy.
FSGS is often an aggressive, progressive condition. As more podocytes become damaged or lost, proteinuria can reach a nephrotic range (3 grams or more per day). More than 70% of newly diagnosed adult patients with primary FSGS have proteinuria in the nephrotic range.1
Further disease progression can cause nephrotic syndrome. Nephrotic syndrome refers to a group of symptoms associated with kidney damage including, proteinuria of ≥3.5 g/d, low levels of blood albumin (≤3.5 g/dL), with or without edema.2
In FSGS, proteinuria is a standard measure of disease activity, and a predictor and contributor to disease progression.3,4
Treatment aims to reduce proteinuria to induce a complete or partial remission which is important for long-term preservation of kidney function. There are no medications specifically approved for FSGS.
FSGS is divided into different types, depending on the cause:2
- Primary – no known cause of FSGS, and with presence of nephrotic syndrome
- Genetic – FSGS caused by abnormal genes that are inherited from a parent
- Secondary – FSGS with a known cause such as viral infection, medications, or conditions that alter the structure of the kidney (e.g., systemic high blood pressure, obesity, sickle cell anemia, transplanted kidney, aging kidney)
- FSGS-UC – FSGS of undetermined cause, and without presence of nephrotic syndrome
The incidence of FSGS in the US has risen over the last 3 decades in children and adults.5-7 Race, ethnicity, and gender all have a significant effect on the incidence of FSGS.8-10 FSGS is more common in people of African ancestry.11 In the US, incidence of FSGS is thought to be 2.7 new cases in 100,000 people per year. Data from the US Renal Data System shows the incidence rate of end-stage kidney disease caused by FSGS increased by 11 times between 1980 to 2000.5
Although rare, FSGS is one of the most common glomerular causes of end-stage kidney disease.
- Korbet. J Am Soc Nephrol. 2012;23:1769-1776.
- KDIGO Clinical Practice Guideline on Glomerular Diseases (Public review draft – June 2020)
- Abbate M, et al. Am J Pathol 2002; 161:2179–2193.
- Abbate M, et al. J Am Soc Nephrol 2006; 17:2974–2984
- Kitiyakara et al. Am J Kidney Dis. 2004;44:815-825.
- Sim et al. Am J Kidney Dis. 2016;68:533-544.
- Haas et al. Am J Kidney Dis. 1995;26:740-750.
- Kitiyakara et al. Semin Nephrol. 2003;23:172-182.
- McGrogan et al. Nephrol Dial Transplant. 2011;26:414-430.
- Sim et al. Am J Kidney Dis.
- Ikechi et al. Port J Nephrol Hypert. 2012;26(1).