While idiopathic, or unknown, diseases are the most common cause of primary childhood nephrotic syndrome, researchers have linked certain diseases and some specific genetic changes that damage the kidneys with primary childhood nephrotic syndrome.
                
The cause of secondary childhood nephrotic syndrome is an underlying disease or infection. Called a primary illness, its this underlying disease or infection that causes changes in the kidney function that can result in secondary childhood nephrotic syndrome.
                
Congenital diseasesdiseases that are present at birthcan also cause childhood nephrotic syndrome.
                
Primary Childhood Nephrotic Syndrome
                
The following diseases are different types of idiopathic childhood nephrotic syndrome:
                
- Minimal change disease involves damage to the glomeruli that can be seen only with an electron microscope. This type of microscope shows tiny details better than any other microscope. Scientists do not know the exact cause of minimal change disease. Minimal change disease is the most common cause of idiopathic childhood nephrotic syndrome.1  - Focal segmental glomerulosclerosis is scarring in scattered regions of the kidney:     - Focal means that only some of the glomeruli become scarred.    - Segmental means damage affects only part of an individual glomerulus.    - Membranoproliferative glomerulonephritis is a group of disorders involving deposits of antibodies that build up in the glomeruli, causing thickening and damage. Antibodies are proteins made by the immune system to protect the body from foreign substances such as bacteria or viruses.
                
Secondary Childhood Nephrotic Syndrome
                
Some common diseases that can cause secondary childhood nephrotic syndrome include
                
- diabetes, a condition that occurs when the body cannot use glucosea type of sugarnormally  - Henoch-Schnlein purpura, a disease that causes small blood vessels in the body to become inflamed and leak  - hepatitis, inflammation of the liver caused by a virus  - human immunodeficiency virus (HIV), a virus that alters the immune system  - lupus, an autoimmune disease that occurs when the body attacks its own immune system  - malaria, a disease of the blood that is spread by mosquitos  - streptococcal infection, an infection that results when the bacteria that causes strep throat or a skin infection is left untreated
                
Other causes of secondary childhood nephrotic syndrome can include certain medications, such as aspirin, ibuprofen, or other nonsteroidal anti-inflammatory drugs, and exposure to chemicals, such as mercury and lithium.
                
Congenital Diseases and Childhood Nephrotic Syndrome
                
Congenital nephrotic syndrome is rare and affects infants in the first 3 months of life.2 This type of nephrotic syndrome, sometimes called infantile nephrotic syndrome, can be caused by
                
- inherited genetic defects, which are problems passed from parent to child through genes  - infections at the time of birth
                
More information about underlying diseases or infections that cause changes in kidney function is provided in the NIDDK health topic, Glomerular Diseases.