Final answer:
The most common cause of idiopathic nephrotic syndrome in adults, accounting for about 50% of cases in African-American patients, is focal segmental glomerulosclerosis (FSGS).
Step-by-step explanation:
Focal Segmental Glomerulosclerosis (FSGS) is the most common cause of idiopathic nephrotic syndrome in adults, particularly noted for accounting for about 50% of cases in African-American patients.
Nephrotic syndrome is characterized by the damage to the glomerulus leading to significant protein loss in the urine, as well as swelling, low serum albumin, and high cholesterol levels. FSGS is a type of glomerulonephritis, which occurs when the filters within the kidneys are damaged, affecting their ability to properly filter waste from the blood.
Other causes of idiopathic nephrotic syndrome in adults include minimal change disease, membranous nephropathy, and membranoproliferative glomerulonephritis. However, FSGS is the most common cause, especially among African-American patients.