Nephrotic syndrome happens when there is a problem with your kidneys’ filters. When your kidneys’ filters are not working in the right way, this can lead to the symptoms of nephrotic syndrome.

This damage to the kidneys’ filters is caused by diseases that damage the kidneys. Some of these diseases affect only the kidneys, and these are called primary causes of nephrotic syndrome. Other diseases affect the whole body, including the kidneys, and these are called secondary causes of nephrotic syndrome. Most people who have nephrotic syndrome have secondary causes.

The most common primary cause of nephrotic syndrome in adults is a disease called focal segmental glomerulosclerosis (FSGS). The most common secondary cause of nephrotic syndrome in adults is diabetes.

In children, the most common primary cause of nephrotic syndrome is minimal change disease. The most common secondary cause of nephrotic syndrome in children is diabetes.