Minimal change disease (MCD): is the most common cause of nephrotic syndrome in children. It owes its name to the fact that the nephrons appear normal when viewed with an optical microscope as the lesions are only visible using an electron microscope. Another symptom is a pronounced proteinuria.
Focal segmental glomerulosclerosis (FSGS): is the most common cause of nephrotic syndrome in adults. It is characterized by the appearance of tissue scarring in the glomeruli. The term focal is used as some of the glomeruli have scars, while others appear intact; the term segmental refers to the fact that only part of the glomerulus suffers the damage.
Membranous glomerulonephritis (MGN): The inflammation of the glomerular membrane causes increased leaking in the kidney. It is not clear why this condition develops in most people, although an auto-immune mechanism is suspected.
Membranoproliferative glomerulonephritis (MPGN): is the inflammation of the glomeruli along with the deposit of antibodies in their membranes, which makes filtration difficult.
Rapidly progressive glomerulonephritis (RPGN): (Usually presents as a nephritic syndrome) A patient’s glomeruli are present in a crescent moon shape. It is characterized clinically by a rapid decrease in the glomerular filtration rate (GFR) by at least 50% over a short period, usually from a few days to 3 months.
They are considered to be "diagnoses of exclusion", i.e. they are diagnosed only after secondary causes have been excluded.