IgM nephropathy in children: clinicopathologic analysis

Introduction: IgM nephropathy (IgMN) is a glomerulonephritis characterized by diffuse mesangial deposits of immunoglobulin M (IgM), which usually presents with nephrotic range proteinuria and, according to some previous studies, occurs most often in patients who are resistant or dependent of steroid treatment. Aim: To perform a clinical, histological and inmunopathological description, and assess response to steroid treatment of pediatric patients diagnosed with nephrotic syndrome and diffuse mesangial deposits of IgM. Methods: This is a descriptive, retrospective study done in two hospitals. Clinical data were taken from medical records. All the slides with the histologic sections were re-evaluated. Results: thirteen children were included in this study. IgMN corresponded to 5.17% of all pediatric renal biopsies. The age of patients ranged from 1 year to 12 years (median: 2 years), 46,15% were women. The most common morphological finding was diffuse mesangial hypercellularity (46,1%), followed by focal segmental glomerulosclerosis (30,8%) and minimal glomerular changes (23,1%). All patients received steroids, in 4 cases (30,7%) as the only immunosuppressant medication, 3 (23,1%) also received cyclophosphamide, 5 (38,4%) mycophenolate, and 1(7.7%) cyclosporine. Seven patients (53,8%) had frequent relapses, 5 (38.5%) were cortico-resistant, and 1 (7.7%) cortico-dependent. Two patients (15,38%) had chronic impairment of renal function. Conclusion: The presence of diffuse mesangial IgM in pediatric patients with nephrotic syndrome is not a too uncommon finding, the clinical presentation has been associated with lower response to steroids, but their long-term prognosis is still unknown.