The significance of
IgM on immunofluorescence in renal biopsy specimens remains unclear. This retrospective case study was conducted to define the clinical features, response to
therapy and outcome of patients with Mesangioproliferative
Glomerulonephritis (MGN) with diffuse
IgM deposition. Of 1919 native renal biopsies performed over a ten-year period, 139 (7.2%) had light microscopic features of MGN and manifested
IgM as the dominant
immunoglobulin. When exclusion criteria (more than a trace of
IgA or
IgG, segmental
IgM, evidence of SLE,
vasculitis, FSGS or
Alport's syndrome and pregnant patients) were applied, 60 patients (3.1%) remained. Follow-up data were available 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.
Creatinine 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 isolated microscopic / macroscopic
hematuria or asymptomatic
proteinuria suffered a decline in renal function.
Protein excretion rate fell into the normal range in 63% of those receiving
steroids, with 82% becoming
steroid dependent. Of those treated with
cyclosporine (48%) or
cyclophosphamide (52%) only 9.5% and 14.5% respectively remained in prolonged remission after discontinuing treatment. It is concluded that MGN with
IgM deposition carries a very favorable prognosis except in patients with NS who develop FSGS. However there is a high incidence of
steroid dependence and resistance in the proteinuric group.