Membranoproliferative Glomerulonephritis (MPGN)

Pathophysiology

1) thickening of glomerular basement membrane with exaggertion of the lobular glomerular tuft Type 1 – 2) immune-complex deposition with subendothelial and mesangial depositis of C3 and IgG or IgM 3) usually secondary to other disease processes Type 2 – 4) electron-dense deposits in glomerular basement membrane with C3 deposition but no immunoglobulin deposition 5) considered autoimmune in nature

Signs and Symptoms

Type 1 – 1) nephritic syndrome (heavy proteinuria, urinary sediment, edema) Type 2 – 2) nephrotic and/or nephritic syndrome 3) has variable course with either stable glomerular filtration rate or progression to end-stage renal disease in 5-10 years

Characteristic Test Findings

Laboratory – 1) type 1 and type 2 have decreased serum complement 2) type 2 has C3 nephritic factor (an IgG autoantibody) that binds to C3 convertase and prevents its inactivation (hence depleting levels of C3)

Associated Conditions

Type 1 – 1) HIV 2) hepatitis B and C 3) lupus 4) cryoglobulinemia 5) bacterial endocarditis 6) leukemia/lymphoma

Treatment

Type 1 – 1) elimination or control of underlying process Type 2 – 2) no effective treatment exists

Tips for USMLE

1) if C3 nephritic factor is mentioned, think membranoproliferative glomerulonephritis 2) type 1 usually presents with nephrotic syndrome; type 2 presents with nephrotic or nephritic syndrome