Idiopathic membranous nephropathy

Idiopathic Membranous Nephropathy
Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Proteinuria, edema, hypertension
Complications	Chronic kidney disease, thromboembolism
Onset
Duration
Types	N/A
Causes	Unknown
Risks
Diagnosis	Renal biopsy, serology
Differential diagnosis	N/A
Prevention	N/A
Treatment	Immunosuppressive therapy, ACE inhibitors, ARBs
Medication	N/A
Prognosis	Variable
Frequency
Deaths	N/A

Idiopathic Membranous Nephropathy (IMN) is a kidney disorder characterized by the thickening of the glomerular basement membrane due to the deposition of immune complexes. It is termed "idiopathic" because the exact cause is unknown, distinguishing it from secondary forms of membranous nephropathy that are associated with other conditions such as lupus erythematosus or hepatitis B.

Pathophysiology

Idiopathic Membranous Nephropathy is primarily an autoimmune disease. The pathogenesis involves the formation of subepithelial immune deposits along the glomerular basement membrane. These deposits are primarily composed of IgG antibodies and complement components, particularly C3. The most common target antigen identified in IMN is the phospholipase A2 receptor (PLA2R) on podocytes.

The immune complex deposition leads to complement activation, particularly the membrane attack complex (C5b-9), which causes podocyte injury and proteinuria. Over time, the continuous immune-mediated damage results in the thickening of the glomerular basement membrane, visible on electron microscopy as "spikes".

Clinical Presentation

Patients with idiopathic membranous nephropathy typically present with nephrotic syndrome, which is characterized by:

• Proteinuria (>3.5 g/day)
• Hypoalbuminemia
• Edema
• Hyperlipidemia

Some patients may also present with hypertension and an increased risk of thromboembolic events due to the hypercoagulable state associated with nephrotic syndrome.

Diagnosis

The diagnosis of idiopathic membranous nephropathy is confirmed through a combination of clinical evaluation, laboratory tests, and renal biopsy.

Laboratory Tests

• Urinalysis: Shows significant proteinuria.
• Blood tests: May reveal hypoalbuminemia and hyperlipidemia.
• Serology: Testing for anti-PLA2R antibodies can support the diagnosis of IMN.

Renal Biopsy

A renal biopsy is essential for the definitive diagnosis. Histological examination typically shows:

• Diffuse thickening of the glomerular capillary walls.
• Subepithelial immune deposits on immunofluorescence microscopy.
• "Spikes" on the glomerular basement membrane seen on electron microscopy.

Treatment

The management of idiopathic membranous nephropathy involves both supportive care and specific therapies aimed at reducing proteinuria and preserving renal function.

Supportive Care

• Blood pressure control: Using ACE inhibitors or angiotensin II receptor blockers (ARBs) to reduce proteinuria and protect renal function.
• Diuretics: To manage edema.
• Statins: To address hyperlipidemia.

Immunosuppressive Therapy

For patients with significant proteinuria or declining renal function, immunosuppressive therapy may be indicated. Options include:

• Corticosteroids
• Cyclophosphamide
• Calcineurin inhibitors (e.g., cyclosporine, tacrolimus)
• Rituximab

Prognosis

The prognosis of idiopathic membranous nephropathy is variable. Some patients may experience spontaneous remission, while others may progress to chronic kidney disease or end-stage renal disease. Factors associated with a poorer prognosis include persistent high-grade proteinuria and declining renal function.

See Also

• Nephrotic syndrome
• Glomerulonephritis
• Chronic kidney disease

External Links

• [Link to relevant nephrology resources]