Idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome (INS) is a kidney disorder characterized by massive proteinuria (excessive protein loss in the urine), hypoalbuminemia (low blood albumin levels), generalized edema (swelling), and hyperlipidemia (elevated blood lipid levels). The term 'idiopathic' indicates that the condition arises without a clearly identifiable underlying cause, distinguishing it from secondary forms of nephrotic syndrome caused by infections, systemic diseases, or drugs. INS is the most common form of nephrotic syndrome in children, though it can also occur in adults. The condition primarily affects the glomeruli — the tiny filtering units within the kidneys — leading to increased permeability of the glomerular filtration barrier to plasma proteins, particularly albumin. Histologically, INS encompasses several subtypes, most notably minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), and membranous nephropathy. In children, minimal change disease accounts for the majority of cases, while FSGS and membranous nephropathy are more common in adults. Patients typically present with periorbital and peripheral edema, foamy urine due to heavy proteinuria, fatigue, and weight gain from fluid retention. Complications can include increased susceptibility to infections (due to loss of immunoglobulins), thromboembolic events (due to loss of anticoagulant proteins), and in some cases, acute kidney injury. The first-line treatment for idiopathic nephrotic syndrome is corticosteroid therapy (typically prednisone or prednisolone), to which the majority of pediatric patients respond favorably — these patients are classified as having steroid-sensitive nephrotic syndrome. However, a significant proportion of patients may be steroid-resistant, steroid-dependent, or frequently relapsing, requiring second-line immunosuppressive agents such as calcineurin inhibitors (cyclosporine, tacrolimus), mycophenolate mofetil, cyclophosphamide, or rituximab. Supportive care includes dietary sodium restriction, diuretics for edema management, and anticoagulation when indicated. While many children with steroid-sensitive INS achieve long-term remission, steroid-resistant forms, particularly FSGS, carry a risk of progression to end-stage kidney disease requiring dialysis or kidney transplantation.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Idiopathic nephrotic syndrome