C3 Glomerulopathy is a disease that affects the kidneys, especially the glomeruli due to abnormalities in a certain portion of the immune system known as the complement pathway.

Nephrotic syndrome is defined by abnormal loss of protein through the kidneys into the urine (greater than 3.5 grams per day in adults and greater than 50 mg/kg per day in children), leading to low protein levels (albumin, in particular) in the blood.

In minimal change disease, the filters don’t function well because their structure is altered. As blood flows through the altered filters, large amounts of proteins can leak into the urine.

Membranous nephropathy is an autoimmune disease in which the body’s immune system targets and attacks the glomeruli. The glomeruli become leaky, leading to abnormal loss of protein in the urine (proteinuria) and a decrease in the ability of the kidneys to filter waste products and excess fluid from the blood.

Lupus nephritis is a kidney disorder that occurs as a result of systemic lupus erythematosus (SLE), an autoimmune disease. In lupus nephritis, the body's immune system attacks the kidney tissues, causing inflammation and kidney damage.

IgA vasculitis, formerly Henoch-Schonlein purpura, is the most common childhood systemic vasculitis (inflammation of small-sized blood vessels). The disease develops after IgA antibodies deposit in the walls of small blood vessels, which results in inflammation.