Focal segmental glomerulosclerosis (FSGS): symptoms, diagnosis and treatment

The kidneys contain about a million tiny filters called glomeruli. Kidney Care UK explains that FSGS describes a particular pattern of scarring on them: focal means some but not all of the glomeruli are affected, segmental means part of each affected glomerulus is scarred, and glomerulosclerosis means scarring of the glomeruli. The National Kidney Federation (NKF) adds that the scarring can only be seen clearly under the microscope, so FSGS is normally only diagnosed after a kidney biopsy.

FSGS is a type of nephrotic syndrome, a rare kidney condition in which too much protein is lost in the urine and too much water is retained in the body. Kidney Care UK says nephrotic syndrome affects around 1 in 10,000 people a year in the UK and about 1 in 4 of these will be diagnosed with FSGS, so FSGS is very rare.

Kidney Care UK describes two main types. Primary or idiopathic FSGS occurs without a clear underlying cause; doctors believe it may be related to factors in the blood that damage the kidney filters, perhaps linked to a fault in the immune system. Secondary FSGS occurs because of other factors such as other medical conditions, medications, reduced kidney tissue, long-term high blood pressure and infections.

The NKF describes the general cause as immunological, with the body's antibodies and white blood cells damaging the kidney by mistake, and says primary, secondary and genetic types exist. In its account secondary FSGS is more common and is associated with high blood pressure, obesity, diabetes, infections such as HIV and certain medicines, while genetic or familial FSGS is very rare. Kidney Care UK says that some cases are due to a genetic mutation that affects the structure of part of the glomerulus, which causes the protein leak, but this is very rare.

The NKF says symptoms are variable and that in many cases there are none, with a routine medical check picking up protein in the urine. Kidney Care UK says people usually develop the symptoms of nephrotic syndrome: protein in the urine, which may make the urine look frothy if there is a lot, and swelling or puffiness (oedema), especially around the eyes and ankles. Swelling around the eyes tends to be worse first thing in the morning, and ankle swelling usually worse in the evenings. The swelling is soft, painless and leaves a dent when pressed.

Other features include an increased risk of infection, anaemia and low blood pressure. During flare-ups people are more at risk of infections or blood clots, particularly in the leg veins. The NKF lists high blood pressure, high cholesterol if there is a lot of protein loss, and kidney failure as possible complications; it adds that kidney failure, if it happens, develops slowly, so a sudden change overnight is not expected.

Kidney Care UK says a doctor may suspect FSGS if you have symptoms of nephrotic syndrome and, for example, visible blood in the urine, passing less urine, high blood pressure, blood tests showing the kidneys are not working properly, being a child or teenager, or nephrotic syndrome that keeps coming back despite treatment. You may be referred to a nephrologist, a kidney specialist.

FSGS is diagnosed by kidney biopsy, in which a tiny sample of one kidney is removed with a special needle and examined under microscopes. Blood tests check protein levels and kidney function, and blood may be taken for genetic testing. Understanding the cause of the FSGS pattern helps doctors choose the right treatment, predict how the condition might progress, and decide whether other family members need testing.

Kidney Care UK says the scarring seen on biopsy is permanent, but the underlying process that causes it can be treated. Successful treatment means achieving remission, when the protein leakage stops (complete remission) or significantly reduces (partial remission). The NKF describes FSGS as not an easy condition to treat, with some people relying on treatment of blood pressure and cholesterol.

• Your kidney team monitors treatment with regular urine tests for protein, blood tests of kidney function, blood pressure checks and monitoring for new symptoms or side effects.

• Kidney Care UK says to contact a doctor if you have a fever above 38 degrees with a sore throat or cough, a rash or severe bruising, or bad stomach pain or repeated vomiting while on steroids.

The NKF says the outcome is very variable and you will need to ask your specialist what is likely in your case. It may continue unchanged for many years needing only regular check-ups, may go away on its own in some cases, or fluid retention may worsen, and in some cases kidney failure develops, leading to haemodialysis or transplantation. Primary and familial FSGS have a slight risk of recurrence even after a kidney transplant, though this varies from person to person.

Kidney Care UK says that some people recover or go into remission, but for most the condition will get worse over time and eventually lead to kidney failure and the need for dialysis or a transplant. The NKF notes that most people with the disease lead normal lives, work and have children, though applying for a mortgage or life insurance may need a medical report, so it suggests planning ahead.

Kidney Care UK points to the Nephrotic Syndrome Trust for more information, including genetics, diagnosis, symptoms and treatment.

FSGS is managed by NHS kidney (renal) teams, with biopsy, blood and urine monitoring, medicines and, where needed, dialysis and transplantation provided free at the point of use. Children with nephrotic syndrome are looked after by paediatric nephrology services.

Some people ask for a private nephrology opinion, for example on treatment choices after a poor response to steroids. Because the biopsy and genetic results guide decisions, it is useful to ask for copies of reports and to share them with any additional specialist.