Clinical and Pathological Faces of IgM Deposition in Children with Idiopathic Nephrotic Syndrome: A Single Center...

Immunoglobulin M nephropathy (IgMN) is a pathological term defining glomerulonephritis with IgM deposition. The clinical significance is still a matter of debate. The aim was to evaluate children with IgM nephropathy (IgMN) in terms of clinical and pathological features, along with treatment responses and outcomes.

The children with idiopathic nephrotic syndrome (INS) who underwent kidney biopsy at our center (n=41) were evaluated retrospectively. Twenty-one children with IgMN were included.

The female to male ratio was 0.9, the median age was 3.5 years in the study group. The mean disease duration and follow-up periods were 11.8 and 11.3years, respectively. At admission, 14% of the patients had hypertension, and 19% had microscopic hematuria. Steroid-dependent nephrotic syndrome (SDNS) was observed in 62% of the patients at admission and 81% at last visit. The patients with IgM (≥2+) depositions had more SDNS than those with IgM (1+). The most common light microscopic diagnosis was mesangial proliferative glomerulonephritis (MesPGN) (47.6%). Focal segmental glomerulosclerosis (FSGS) elevated significantly from 14% at initial biopsy to 57% at follow-up biopsies. Patients who progressed to FSGS mostly had C3 co-deposition, high IgM intensity (≥2+), diagnosis of MesPGN, and SDNS clinic. The most frequently used adjuvant agent was cyclosporine-A (n=19) with mean duration of 68 months. It provided lower relapse rates. Rituximab (n=4) showed 75% remission rate. None of the patients had needed renal replacement treatment. Two patients who were steroid-resistant at admission had FSGS in their first biopsies, acted as multi-drug resistance at follow-up, and ended up in Stage-2 chronic kidney disease (CKD).

This study shows IgMN is mainly presented with SDNS clinic and MesPGN pathology. Evolution to FSGS may be related to steroid resistance, MesPGN, high IgM intensity, and C3 co-deposition.