Nephrotic syndrome is a condition where the kidneys are not working properly, causing protein in the urine, low protein levels in blood, and swelling. It is usually caused by damage to the small blood vessels in the kidneys that filter waste. The main causes are chronic glomerulonephritis, amyloidosis which damages blood vessels, and minimal change nephrotic syndrome where the kidneys lose negative charges. It causes excess protein loss in the urine and low blood protein levels, resulting in fluid building up in tissues and causing edema.