Primary glomerulonephritis with predominant mesangial Immunoglobulin G deposits

Glomerular deposits are a major pathologic feature of a wide range of human glomerulonephritis and may be located in the mesangial, subepithelial, and subendothelial regions. Rare cases of primary glomerulonephritis definied by exclusive or predominant mesangial IgG deposits were reported. We reviewed the pathologic findings for the 848 renal biopsies examined in our department between 2007 and 2016, one case of primary mesangial IgG glomerulonephritis (MIG) in the absence of any evidence of systemic lupus erythematous (SLE), of other systemic diseases or of Infections.

Male patient aged 55 years consults for nephrotic syndrome (proteinuria=7g/1.73m2/day; Albuminemia=14g/L) with hematuria.. The serum creatinine concentration was 88 µmol/l, and the creatinine clearance was on MDRD at 82 ml/min/1.73m2. He had a renal biopsy showing the absence of proliferative lesions and the presence of exclusive mesangial IgG deposit. CH50, C3 and C4 levels were normal and antinuclear antibody and anti-DNA antibody assays remained negative during the follow-up period. A full dose corticosteroid was initiated (1mg/Kg/day). The interval from onset of steroid therapy to remission was 2 months. During follow-up; the patient had developed 2 relapsing nephrotic syndrome episods. Then he was switched to Mycophenolate mofetil with remission after 2 months.

MIG is a very rare but distinct type of primary glomerulonephritis that is characterized by exclusive or predominant mesangial IgG deposits. Its renal prognosis may be less favorable than previously reported because of the possibility of steroids resistance of the nephrotic syndrome and the recurrence after renal transplantation.