Clinicopathologic characteristics and steroid response of IgM nephropathy in children presenting with idiopathic nephrotic syndrome.

There is no detailed information on clinical and immunopathologic features of immunoglobulin M nephropathy (IgMN) in children with idiopathic nephrotic syndrome (INS) in Pakistan. We reviewed our native renal biopsies over 15 years (July 1995-July 2010) and identified 135 cases of IgMN in nephrotic children (≤17 years). Their demographic, clinical and immunopathologic data were retrieved from biopsy reports and case notes. Mean age of this cohort was 7.6 ± 4.2 years. Males were 92 (68.1%) and females were 43 (31.9%). Steroid-dependent NS was seen in 88 (65.2%) cases and steroid-resistant NS in 47 (34.2%). Hematuria was found in 42 cases (31.2%) and hypertension in 27 (19.5%). The most common morphologic change was glomerular mesangial proliferation, found in 89 (65.9%) biopsies. Minor changes were seen in 46 (34.1%) cases and focal segmental glomerulosclerosis (FSGS) in 37 (27.4%). Immunofluorescence microscopy showed diffuse mesangial positivity of IgM in all cases. C3 and C1q were found in 72 (53.3%) and 40 (29.7%) cases, respectively. Our results show that IgMN is a fairly common cause of INS in children in Pakistan. It shows a spectrum of morphologic changes ranging from minor changes to FSGS.