Nephrotic syndrome is characterized by proteinuria, low protein levels, edema, and high cholesterol. It is caused by increased permeability of the glomerular basement membrane, allowing protein to pass into the urine. Symptoms include edema, fatigue, and abdominal pain. Laboratory tests show protein in the urine, low serum protein and albumin levels, and elevated cholesterol. Treatment focuses on restricting salt and protein intake, using diuretics to control edema, and treating the underlying cause, often by using corticosteroids or other immunosuppressive drugs. The prognosis depends on the cause, with minimal change disease often responding well to treatment.