Membranoproliferative glomerulopathy(MPGN) may be idiopathic or associated with a number of other diseases. An important recent recognition is the association with hepatitis C, which may account for 10% to 20% of adult MPGN(see later).
Idiopathic MPGN is a disease of young persons, with most cases diagnosed in those between the ages of 5 and 30 years. Overall, MPGN ac counts for 10% to 15% of all cases of idiopathic nephrotic syndrome.
The clinical manifestations are variable, with around 50% presenting with nephrotic syndrome, 25% to 30% with asymptomatic proteinuria, and 15% to 20% with acute nephritic syndrome, Regardless of the major pattern, concurrent hematuria and proteinuria are almost always present. Serum C3 levels are depressed in more than 70% of patients at disease onset. The presence of C3 nephritic factor is most likely an associated event rather than a cause of MPGN, and its presence does not appear to alter the prognosis . Thus, MPGN must be differentiated from other forms of GN showing hypocomplementemia. MPGN is characterized overall by thickening of capillary loops and mesangial hypercellularity, often with lobular accentuation. Several subtypes exist. Type I MPGN has subendothelial deposits with mesangial interposition producing capillary loop splitting. Type II(dense deposit disease[DDD]) has characteristic broad, very electron-dense deposits widening the GBM. Immunofluorescence examination of both types I and II cells shows extensive granular C3 deposition in the capillary loops, usually with absence of immunoglobulins. There are several different morphologic variants with features similar to either type I or II MPGN that have been reported as type III MPGN MPGN is a slow but progressive disease, with approximately 30% of patients in chronic renal failure at the end of 10 years. Poor prognostic indicators include the presence of nephrotic syndrome or azotemia at the time of diagnosis.
Spontaneous remission of proteinuria occasionally occurs but does not usually affect the long-term outcome. There is currently no consensus on any given therapeutic regimen that is both safe and effective in MPGN, although a combination of corticosteroid and cytotoxic drug therapy antiplatelet agents have been used.
Type II MPGN recurs in virtually 100% of renal transplants, but recurrence is far less common in type I MPGN(about 25%). However, recurrence does not interfere with long-term graft survival.