Nephrotic syndrome (NS) is a condition that is often caused by any of a group of diseases that damage the kidneys’ filtering system, the glomeruli. The structure of the glomeruli prevents most protein from getting filtered through into the urine. Normally, a person loses less than 150mg of protein in the urine in a 24-hour period. Proteinuria is the primary indicator of NS. There are a number of different disorders that can cause NS. Diabetes and, to a lesser extent, hypertension can cause diffuse damage to the glomeruli and can ultimately lead to NS. The following diseases can cause specific damage to the glomeruli and often result in the development of heavy proteinuria and in many instances NS:

• Amyloidosis (the stiffening and subsequent malfunction of the kidney due to fibrous protein deposit in the tissue)
• Congenital nephrosis
• Focal segmental glomerular sclerosis (FSGS) (creates scar tissue in the glomerulus, damaging its protein-repellant membrane)
• Glomerulonephritis
• Diffuse mesangial proliferative GN (affecting the messangium)
• Membranous (damages the protein-repellant membrane)
• Postinfectious
• IgA nephropathy (Berger’s disease) (deposit of specific immunoglobulin A causing an inflammatory reaction and leading to glomerulonephritis)
• Minimal change disease (Nil’s disease)
• Pre-eclampsia, though rarely resulting in NS, is more often limited to heavy proteinuria

Diagnosis of this condition will include a physical examination and the assessment of family health history, along with blood tests, urinalysis and likely a kidney biopsy. A closed kidney biopsy may be used to determine the underlying cause and extent of disease with the exception of the following cases.

The outcome of NS varies and is largely dependent on the underlying cause. Some patients may have a spontaneous recovery not requiring any specific therapy, while others worsen despite aggressive, specific therapy.