Causes of Nephrotic Syndrome
Nephrotic syndrome can be caused by diseases that affect only the kidneys, such as focal segmental glomerulosclerosis (FSGS) or membranous nephropathy. Diseases that affect only the kidneys are called primary causes of nephrotic syndrome. The glomeruli are usually the targets of these diseases for reasons that are not fully understood. In FSGS-the most common primary cause of nephrotic syndrome-scar tissue forms in parts of the glomeruli. In membranous nephropathy, immune molecules form harmful deposits on the glomeruli.

Nephrotic syndrome can also be caused by systemic diseases, which are diseases that affect many parts of the body, such as diabetes or lupus. Systemic diseases that affect the kidneys are called secondary causes of nephrotic syndrome. More than 50 percent of nephrotic syndrome cases in adults have secondary causes, with diabetes being the most common.