Concept
Membranoproliferative glomerulonephritis (MPGN) is a type of glomerulonephritis caused by deposits in the kidney glomerular mesangium and basement membrane (GBM) thickening, activating complement and damaging the glomeruli. MPGN accounts for approximately 4% of primary renal causes of nephrotic syndrome in children and 7% in adults. It should not be confused with membranous glomerulonephritis, a condition in which the basement membrane is thickened, but the mesangium is not. There are three types of MPGN, but this classification is becoming obsolete as the causes of this pattern are becoming understood. Type I, the most common by far, is caused by immune complexes depositing in the kidney. It is characterised by subendothelial and mesangial immune deposits. It is believed to be associated with the classical complement pathway. Eculizumab#Dense-deposit disease (DDD) Also called recently as ‘C3 nephropathy’ The preferred name is "dense deposit disease." Most cases of dense deposit disease do not show a membranoproliferative pattern. A 2012 review considers DDD to be in a continuum with C3 glomerulonephritis, one reason the use of the type I to type III classification system is falling out of favour. Most cases are associated with the dysregulation of the alternative complement pathway. DDD is associated with deposition of complement C3 within the glomeruli with little or no staining for immunoglobulin. The presence of C3 without significant immunoglobulin suggested to early investigators that DDD was due to abnormal activation of the complement alternative pathway (AP). There is now strong evidence that DDD is caused by uncontrolled AP activation. Spontaneous remissions of MPGN II are rare; approximately half of those affected with MPGN II will progress to end stage renal disease within ten years. In many cases, people with MPGN II can develop drusen caused by deposits within Bruch's membrane beneath the retinal pigment epithelium of the eye. Over time, vision can deteriorate, and subretinal neovascular membranes, macular detachment, and central serous retinopathy can develop.
