(See also Overview of Nephrotic Syndrome.)
Membranoproliferative glomerulonephritis is a group of immune-mediated disorders characterized histologically by glomerular basement membrane (GBM) thickening and proliferative changes on light microscopy. There are 3 types, each of which may have primary (idiopathic) or secondary causes. Primary forms affect children and young adults between ages 8 and 30 and account for 10% of cases of nephrotic syndrome in children; secondary forms tend to affect adults > 30. Men and women are affected equally. Reported familial cases of some types suggest genetic factors play a role in at least some cases. Many factors contribute to hypocomplementemia.
Type I (mesangial proliferation with immune deposits) accounts for 80 to 85% of cases. The idiopathic form is rare. Type I most commonly occurs secondary to one of the following:
Other disorders (eg, partial lipodystrophy, C2 or C3 deficiencies, sarcoidosis, thrombotic microangiopathies)
Type II (similar to type I with less mesangial proliferation and with GBM dense deposits) accounts for 15 to 20%. It is probably an autoimmune disorder in which an IgG autoantibody (C3 nephritic factor) binds C3 convertase, rendering C3 resistant to inactivation; immunofluorescent staining identifies C3 around dense deposits and in mesangium.
Type III is thought to be a disorder similar to type I and accounts for few cases. Cause is unknown but may be related to immune complex (IgG, C3) deposition. An IgG autoantibody against the terminal component of complement is found in 70% of patients. Subepithelial deposits can occur focally and appear to disrupt the GBM.
Symptoms and signs are those of nephrotic syndrome in 60 to 80% of cases. Symptoms and signs of nephritic syndrome (acute glomerulonephritis) are presenting features in 15 to 20% of cases of type I and III disease and in a higher percentage of type II disease. At diagnosis, 30% of patients have hypertension and 20% have renal insufficiency; hypertension often develops even before glomerular filtration rate (GFR) declines.
Patients with type II disease have a greater incidence of ocular abnormalities (basal laminar drusen, diffuse retinal pigment alterations, diskiform macular detachment, choroidal neovascularization), which ultimately impair vision.
Diagnosis is confirmed by renal biopsy. The location of immune complex deposits can help differentiate between types; typically subendothelial and mesangial in type I, intramembranous in type II, and subepithelial in type III. Other tests are also done.
Serum complement profiles are more frequently abnormal in membranoproliferative glomerulonephritis than in other glomerular disorders and provide supportive evidence of the diagnosis (see table Serum Complement Profiles in Membranoproliferative Glomerulonephritis). C3 levels are often low. In type I disease, the classic complement pathway is activated and C3 and C4 are decreased. C3 may be decreased more often than C4 at diagnosis and decreases further during follow-up, but eventually normalizes. In type II disease, the alternate complement pathway is activated and C3 is more frequently and severely reduced than in type I while C4 levels are normal. In type III disease, C3 is reduced but C4 is normal. C3 nephritic factor is detectable in 80% of patients with type II and in some patients with type I disease. Terminal complement nephritic factor is detectable in 20% of patients with type I, rarely in patients with type II, and 70% of patients with type III disease.
Serum Complement Profiles in Membranoproliferative Glomerulonephritis
Complete blood count (CBC), often obtained in the course of diagnostic evaluation, demonstrates normochromic-normocytic anemia, often out of proportion to the stage of renal insufficiency (possibly because of hemolysis), and thrombocytopenia from platelet consumption.
Prognosis is good if a condition causing secondary membranoproliferative glomerulonephritis is successfully treated. Idiopathic type I membranoproliferative glomerulonephritis often progresses slowly; type II progresses more rapidly. In general, the long-term prognosis is poor. End-stage renal disease occurs in 50% of patients at 10 years and in 90% at 20 years. Spontaneous remission occurs in < 5% with type II. Type I membranoproliferative glomerulonephritis recurs in 30% of kidney transplantation patients; type II recurs in 90% but, despite this high recurrence rate, leads to graft loss only infrequently. Outcome tends to be worse if proteinuria is in the nephrotic range.
Corticosteroids for children with nephrotic-range proteinuria
Dipyridamole and aspirin for adults
Kidney transplantation for patients with end-stage renal disease
Underlying disorders are treated when possible. Specific therapy is probably not indicated for patients with non-nephrotic–range proteinuria, which usually suggests slow progression.
Among children with nephrotic-range proteinuria, treatment with corticosteroids (eg, prednisone 2.5 mg/kg orally once a day on alternate days [maximum 80 mg/day]) for 1 year, followed by tapering to a maintenance dose of 20 mg on alternate days for 3 to 10 years, may stabilize renal function. However, corticosteroid treatment may retard growth and cause hypertension.
Among adults, dipyridamole 225 mg orally once a day with aspirin 975 mg orally once a day for 1 year may stabilize renal function at 3 to 5 years, but at 10 years there is no difference from placebo. Studies of antiplatelet therapy yield inconsistent results.
Alternate therapies are sometimes substituted for the usual treatments (eg, corticosteroids could exacerbate underlying hepatitis C). Alternative therapies include pegylated interferon alfa-2a or pegylated interferon alfa-2b (with addition of ribavirin if creatinine clearance is >50 mL/min) for hepatitis C virus–associated disease and plasma exchange with corticosteroids for concomitant severe cryoglobulinemia or rapidly progressive glomerulonephritis. Angiotensin-converting enzyme (ACE) inhibitors may decrease proteinuria and help control hypertension.
Membranoproliferative glomerulonephritis is a group of immune-mediated disorders with some common histologic features.
Patients most often present with nephrotic syndrome, but they may present with nephritic syndrome.
Confirm the diagnosis with renal biopsy and obtain serum complement profile and serologic tests.
Treat children who have nephrotic range proteinuria with corticosteroids.