Nephrotic syndrome is urinary excretion of > 3 g of protein/day due to a glomerular disorder plus edema and hypoalbuminemia. It is more common among children and has both primary and secondary causes. Diagnosis is by determination of urine protein/creatinine ratio in a random urine sample or measurement of urinary protein in a 24-h urine collection; Researchers have found that medications are not effective in treating congenital nephrotic syndrome, and that most children will need a kidney transplant by the time they are 2 or 3 years old. A kidney transplant is surgery to place a healthy kidney from someone who has just died or a living donor, most often a family member, into a person’s body to take over the job of the failing kidney.
Proteinuria occurs because of changes to capillary endothelial cells, the glomerular basement membrane (GBM), or podocytes, which normally filter serum protein selectively by size and charge. In nephrotic syndrome, a variety of disorders cause proteinuria, often resulting in marked edema and hypoalbuminemia. The disorder results in urinary loss of macromolecular proteins, primarily albumin but also opsonins, immunoglobulins, erythropoietin , transferrin, hormone-binding proteins (including thyroid-binding globulin and vitamin D-binding protein), and antithrombin III. Deficiency of these and other proteins contribute to a number of complications.