Membranoproliferative glomerulonephritis (MPGN) is classified as Type I, II or III based on the ultrastructural alterations to the glomerular basement membrane. Whereas Type II has long been recognized as clinically and pathologically unique, Types I and III are often difficult to distinguish and, thus, in most clinical studies have not been separated. We report a retrospective review of long term follow-up of all patients with either Type I or III MPGN followed at our institution since 1960. During that period 22 patients with Type I and 24 with Type III MPGN were diagnosed and followed for at least 5 years.
Patients with Type I and Type III MPGN did not differ with respect to age at presentation, age at diagnosis, or interval from onset of symptoms to diagnosis. They had similar presentations and initial serum C3 and albumin levels. However, patients with Type I had a significantly lower initial mean estimated GFR compared to patients with Type III (99.6±39.1 vs 135.1±34.0 ml/min/1.73m2 p=0.03). Type of therapy (primarily alternate day prednisone), duration of therapy, length of follow-up, and rate of complications did not differ between groups. Patients with Type III had significantly lower mean C3 levels after 1 year of therapy (77.16±50.72 mg/dl vs 124.63±60.19, p=0.004) and a longer mean duration of hypocomplementemia. At last follow-up, patients with Type I had a slight improvement in mean estimated GFR (+6.6±47.6 ml/min/1.73m2), whereas patients with Type III had a 20% decrease in mean estimated GFR(-27.5±50 ml/min/1.73m2, p=0.04). In addition, patients with Type III had significantly more residual urinary abnormalities than patients with Type I, specifically persistent proteinuria (81% and 41%, p=0.02), and persistent hematuria (33% vs 0%, p=0.03).
