FSGS (focal segmental glomerulosclerosis): causes, symptoms and treatment

Kidney Care UK explains that FSGS describes a particular pattern of scarring. Your kidneys contain about a million tiny filters called glomeruli, which can be damaged and scarred by nephrotic syndrome. The name breaks down into three parts.

• Focal: some but not all of the glomeruli are affected.

• Segmental: a segment (part) of each affected glomerulus is scarred.

• Glomerulosclerosis: there is scarring on the glomeruli (sclerosis means scarring).

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

The NHS says nephrotic syndrome in children is most often "minimal change disease", and lists glomerulosclerosis among the kidney problems that can cause nephrotic syndrome, tending to be more common in adults.

The National Kidney Federation says symptoms vary from case to case. In many cases there are no symptoms, but the damage to the glomeruli causes some protein to appear in the urine, so a routine check may pick it up.

Kidney Care UK says that if you have kidney damage with the FSGS pattern, you usually develop symptoms of nephrotic syndrome.

• Protein in the urine (proteinuria): this is likely to be seen only under a microscope or on a urine dipstick, but with a lot of protein the urine may look frothy.

• Swelling or puffiness (oedema), especially around the eyes and ankles. Swelling around the eyes tends to be worse first thing in the morning; ankle swelling is usually worse in the evenings. The swelling is soft, leaves a dent when pressed and is not painful. It is not an allergic reaction but is caused by the kidneys retaining too much water.

• Increased risk of infection.

• Anaemia and low blood pressure.

Kidney Care UK describes two main types. Primary (idiopathic) FSGS occurs without a clear underlying cause. Doctors believe it may be related to factors in the blood that damage the kidney filters, possibly linked to a fault in the immune system. Secondary FSGS occurs because of other factors.

The National Kidney Federation also describes genetic or familial FSGS as very rare, and says secondary FSGS is more common than primary. Kidney Care UK notes some cases are due to a genetic mutation affecting the structure of part of the glomerulus, though a genetic cause is very rare.

Kidney Care UK says FSGS is diagnosed by a kidney biopsy, in which a tiny piece of one of your kidneys is removed with a special needle and examined under microscopes. Blood tests check protein levels in the blood and kidney function, and blood may be taken for genetic testing.

Your doctor may suspect FSGS if you have symptoms of nephrotic syndrome and also have visible blood in your urine, are urinating less often or in smaller amounts, have high blood pressure, show reduced kidney function on blood tests, are a child or teenager, or have nephrotic syndrome that keeps coming back in spite of treatment. You may be referred to a nephrologist (a specialist kidney doctor).

Understanding the cause matters, Kidney Care UK says, because it helps choose the right treatment, predict how the condition might progress, show whether other family members need testing and guide decisions about long-term care.

Kidney Care UK explains that the scarring pattern seen on a biopsy is permanent, but the underlying process causing it can be treated. Successful treatment means achieving remission: the protein leakage stops (complete remission) or significantly reduces (partial remission). Some people continue to have protein leakage despite treatment.

Kidney Care UK says your team monitors treatment with regular urine tests for protein, blood tests for kidney function, blood pressure checks and watching for new symptoms or side effects.

Contact your doctor if you have any of the following while taking steroids: fever (above 38 degrees C) with a sore throat or cough; a rash or severe bruising; bad stomach pain or repeated vomiting, because steroids can sometimes cause stomach ulcers.

The National Kidney Federation notes high blood pressure may develop and should be treated vigorously, and that high protein loss can raise cholesterol, sometimes needing diet change and cholesterol-lowering drugs.

The outlook is very variable. The National Kidney Federation lists the possibilities: it may continue unchanged for many years, needing only regular check-ups; it may go away on its own in some cases; fluid retention may get worse; or kidney failure may develop, leading to dialysis or transplantation. If kidney failure occurs it develops slowly, so it is not a sudden change overnight.

Kidney Care UK is more cautious: some people recover or go into remission, but for most the condition will get worse over time and eventually lead to kidney failure. The two UK charities therefore differ in emphasis, so ask your own kidney team what to expect in your case.

The National Kidney Federation also says most people with the disease lead normal lives, going to work and having children, though there may be queries when applying for a mortgage or life insurance. Primary and familial FSGS have a slight risk of recurrence even after a kidney transplant.

Kidney Care UK notes a doctor may suspect FSGS in a child or teenager with nephrotic syndrome, especially if it keeps relapsing in spite of treatment. The NHS says most children with nephrotic syndrome have minimal change disease, respond well to steroids and are not at risk of kidney failure, but a small number have inherited (congenital) nephrotic syndrome and usually do less well.

The NHS says children diagnosed for the first time are normally prescribed at least a 4-week course of prednisolone, followed by a smaller dose every other day for 4 more weeks, and that relapses become less frequent with age and often stop by the late teens. It also advises the pneumococcal vaccine and says live vaccines should not be given during certain periods, so check with the child's kidney team.

See a GP if you notice persistent swelling around the eyes or ankles, frothy urine, or blood in your urine. Kidney Care UK says during flare-ups people are at higher risk of infections and of blood clots, particularly in the veins of the leg, so seek prompt medical advice for a hot, painful, swollen leg, a fever, or breathlessness or chest pain, and call 999 if these are severe.

On the NHS, a GP who finds protein in the urine or other signs will arrange blood and urine tests and refer you to a nephrologist, who arranges the kidney biopsy and treatment. Ongoing monitoring is usually with a kidney clinic. Children are seen by a paediatric kidney specialist.

Some people see a nephrologist privately for a quicker opinion. The biopsy, genetic testing and treatment choices are the same, and your NHS team will usually carry on long-term monitoring, so ask for letters to be copied to your GP.