RESUMO
INTRODUCTION: IgM nephropathy (IgMN) is a glomerulonephritis characterised by diffuse mesangial immunoglobulin M (IgM) deposits. It usually presents with nephrotic range proteinuria and, according to some previous work, it occurs most often in patients who are resistant to or dependent on steroid treatment. OBJECTIVE: To perform a clinical, histological and immunopathological description and assess the response to steroid treatment of paediatric patients diagnosed with nephrotic syndrome and diffuse mesangial IgM deposits. METHOD: This is a descriptive, retrospective study carried out in two hospitals, where the clinical records of paediatric patients with IgMN were analysed and the histological sections were re-assessed. RESULTS: thirteen children were included in this study. IgMN corresponded to 5.17% of all paediatric renal biopsies. The age of patients ranged from 1 year to 12 years (median: 2 years), 46.7% 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 paediatric patients with nephrotic syndrome is not a very uncommon finding; its clinical presentation has been associated with lower response to steroids. However, the long-term prognosis of these patients is still unknown.