Minimal change disease is a kidney disorder that can lead to nephrotic syndrome, although the nephrons of the kidney look normal under a regular microscope.

Each kidney is made of more than a million units called nephrons, which filter blood and produce urine.

In minimal change disease, there is damage to the glomeruli -- the tiny blood vessels inside the nephron. The disease gets its name because this damage isn't visible under a regular microscope. It can only be seen under an electron microscope.

Minimal change disease is the most common cause of nephrotic syndrome in children. It is also frequently seen in adults.

The cause is unknown, but the disease may occur after:

• Allergic reactions
• Recent immunizations
• Viral infection

There may be symptoms of nephrotic syndrome:

• Foamy appearance of the urine
• Poor appetite
• Swelling (especially around the eyes, feet and ankles, and in the abdomen)
• Weight gain (from fluid retention)

Minimal change disease does not reduce the amount of urine produced. It rarely progresses to kidney failure.

The doctor may not be able to see any obvious outward signs of the disease, other than swelling. Blood and urine tests reveal signs typical of nephrotic syndrome, including:

• High cholesterol
• High levels of protein in the urine
• Low levels of albumin in the blood

A kidney biopsy and examination of the tissue with an electron microscope can show signs of minimal change disease. An immunofluorescence exam of the biopsied kidney tissue is negative.

Corticosteroids can cure minimal change disease in most children. Some patients may need to stay on steroids to keep the disease in remission.

Adults do not respond to steroids quite as well as children, but many still do find steroids effective. Adults may have more frequent relapses and steroid dependence.

Frequent relapsers (more than three relapses) may need cytotoxic therapy. In most cases, this involves a course of cyclophosphamide. Other medicines that have been used include cyclosporine and chlorambucil.

Swelling may be treated with:

• ACE inhibitor medicines
• Blood pressure control
• Diuretics (water pills)

You may receive instructions on how much salt to allow in your diet.

Minimal change disease usually responds well to corticosteroids, often within the first month. A relapse can occur, but patients may improve after prolonged treatment with corticosteroids and medications that suppress the immune system (immunosuppressive medications).

• Nephrotic syndrome
• Side effects of medications

Call for an appointment with your health care provider if you develop symptoms of minimal change disease.

If you have this disorder, call for an appointment with your health care provider if your symptoms worsen or you develop new symptoms, including side effects from the medications used to treat the disorder.

There is no known prevention.