Mesangioproliferative glomerulonephritis with IgM deposition: Clinical characteristics and outcome

The significance of IgM on immunofluorescence in renal biopsy specimens rem ains unclear. This retrospective case study was conducted to define the cli nical features, response to therapy and outcome of patients with Mesangiopr oliferative Glomerulonephritis (MGN) with diffuse IEM deposition. Of 1919 n ative renal biopsies performed over a ten-year period, 139 (7.2%) had light microscopic features of MGN and manifested IgM as the dominant immunoglobu lin. When exclusion criteria (more than a trace of IgA or IgG, segmental Ig M, evidence of SLE, vasculitis. FSGS or Alport's syndrome and pregnant pati ents) were applied, 60 patients (3.1%) remained. Follow-up data were availa ble for 54 cases with a mean age of 26.5 years (range 1.7-63). Mean follow- up period was 7.4 years (range 4.7-22.2). Forty-one per cent presented with nephrotic syndrome (NS), 26% with asymptomatic proteinuria (>250mg/24hr), 18% with macroscopic hematuria and 15% with isolated microscopic hematuria. Twenty-one percent of patients were hypertensive at presentation. Creatini ne was initially <120(mol/L in all but one patient. Only four patients (7.4 %), all nephrotic, suffered a decline in renal function despite treatment; all 4 developed ESRF after a mean of 5.6 years (range 2-8.3). Two of these were subsequently re-biopsied and found to have FSGS. No patients with isol ated microscopic / macroscopic hematuria or asymptomatic proteinuria suffer ed a decline in renal function. Protein excretion rate fell into the normal range in 63% of those receiving steroids, with 82% becoming steroid depend ent. Of those treated with cyclosporine (48%) or cyclophosphamide (52%) onl y 9.5% and 14.5% respectively remained in prolonged remission after discont inuing treatment. Tt is concluded that MGN with IgM deposition carries a ve ry favorable prognosis except in patients with NS who develop FSGS. However there is a high incidence of steroid dependence and resistance in the prot einuric group.