Minimal change disease: the most common cause of nephrotic syndrome in children

The kidneys contain millions of tiny filters called glomeruli. Kidney Research UK explains that normally protein in the blood is too large to pass through the tiny holes in the filters, but when the glomeruli are damaged large amounts of protein leak into the urine, which results in low levels of protein in the blood and fluid retention. This is called nephrotic syndrome.

Minimal change disease is the most common cause of nephrotic syndrome in children. The NHS says that in these children the kidneys appear normal or nearly normal if a tissue sample is studied under a microscope, with changes visible only under an extremely powerful electron microscope, which is where the name comes from. It adds that the cause is unknown.

The NHS also notes that nephrotic syndrome can sometimes occur as a result of another kidney problem or condition, such as glomerulosclerosis, glomerulonephritis, infections such as HIV or hepatitis, lupus, diabetes, sickle cell disease and, in very rare cases, certain cancers, and that these tend to be more common in adults.

The first sign is usually swelling. Kidney Research UK says swelling is the most noticeable symptom, especially around the eyes and face, which can be worse first thing in the morning, with fluid collecting later in the day in the fingers, legs and abdomen. The swelling is soft and leaves a temporary dent if you press on it. The NHS describes the main features of nephrotic syndrome.

• Swelling (oedema), usually first noticed around the eyes, then the lower legs and the rest of the body.

• Frothy urine because of the protein passing into it, and sometimes passing less urine than usual during relapses.

• A greater chance of infections, because antibodies are lost in the urine.

• An increased risk of potentially serious blood clots.

• Breathlessness in some people if there is fluid around the lungs, according to Kidney Research UK.

The NHS says nephrotic syndrome can usually be diagnosed by dipping a dipstick into a urine sample, with a colour change if there is a large amount of protein, and a blood test showing a low level of albumin confirms the diagnosis. Kidney Research UK adds that blood and urine tests can also measure kidney function and check cholesterol, which is often raised.

In some cases, particularly when initial treatment does not work, a child may need a kidney biopsy, in which a very small sample of kidney tissue is removed and examined. Kidney Research UK says a biopsy may be required to confirm the exact cause, and that children may be offered genetic testing to see if the condition is resistant to steroids.

The NHS says children diagnosed with nephrotic syndrome for the first time are normally prescribed at least a 4-week course of the steroid prednisolone, followed by a smaller dose every other day for 4 more weeks, which stops protein leaking into the urine. For short courses there are usually no serious or long-lasting side effects, although some children get increased appetite, weight gain, red cheeks or mood changes. Most children respond well, with the protein often disappearing from the urine and the swelling going down within a few weeks, a period known as remission.

Other treatments are used alongside or instead of steroids when needed. The NHS lists diuretics to help reduce fluid build-up, penicillin during relapses to reduce infection chances, reducing salt in the diet, and the pneumococcal vaccine, with chickenpox vaccination between relapses for some children. Live vaccines such as MMR, chickenpox and BCG should not be given while a child is taking medication to control symptoms. If remission cannot be maintained with steroids or there are significant side effects, other medicines may be used, such as levamisole, cyclophosphamide, ciclosporin, tacrolimus, mycophenolate or rituximab, and in severe cases albumin infusions in hospital.

The NHS says that if a child has been diagnosed, the family will need to monitor the condition daily. You test the first urine of the day with a dipstick for protein and record the result in a diary for the doctor or specialist nurse. If the dipstick shows 3+ or more protein for 3 days in a row, this means the child is having a relapse and you should follow the advice given about starting steroids or contact the doctor.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if the child has come into contact with someone who has chickenpox or measles and is not immune, is unwell or has a high temperature, or has diarrhoea and is being sick.

Minimal change disease can also occur in adults, although the NHS pages used here focus on children. Kidney Research UK describes nephrotic syndrome as able to occur at any age and lists minimal change nephropathy among the causes. The NHS says causes such as other kidney diseases, infections, lupus and diabetes tend to be more common in adults, which is one reason adults are more likely to have a kidney biopsy to find the exact cause.

The pages used here do not give adult-specific treatment details or figures, so a kidney specialist (nephrologist) can explain what applies in an individual case.

The NHS says most children with nephrotic syndrome respond well to steroids and are not at risk of kidney failure, but a small number with congenital (inherited) nephrotic syndrome usually do less well. Relapses become less frequent with age and often stop by the late teens.

Kidney Research UK says response to treatment varies a lot depending on the underlying cause, that some people respond well to one course of steroids, others need repeated courses and others may not respond at all, in which case kidneys can eventually fail after years of heavy protein leakage.

The NHS notes that a child with nephrotic syndrome may be referred to a childhood kidney specialist (paediatric nephrologist) for tests and specialist treatment, and that families need to monitor their child at home between appointments.

Kidney Research UK points families to the Nephrotic Syndrome Trust and the NephCure Foundation for further information and support, and suggests speaking to your kidney specialist or nurse specialist with any questions or concerns.