What's new in medical renal pathology 2025: Updates on podocytopathy and immunofluorescence staining in medical kidney

Abstract

Diffuse podocytopathy, including minimal change disease and primary focal segmental glomerulosclerosis, is a common cause of nephrotic syndrome in adults and children. It is increasingly recognized to be autoimmune-mediated associated with anti-nephrin and other emerging anti-slit diaphragm antibodies, and can recur in the kidney allograft. Immunofluorescence is routinely used in evaluation of kidney biopsies, and updates include those on fibrillar diseases, monoclonal staining, lupus-like staining, and use of antibody KM55 in IgA-dominant glomerulonephritis.

Fig. 1.

Immunofluorescence staining in diffuse podocytopathy (DP) (Scale bars 20um) (contributed by Dr. Weins). (A) Fine punctate podocyte IgG in autoimmune DP. (B) Overlap of IgG and nephrin in anti-nephrin DP. (C) DP lacking overlap of background IgG with nephrin.

Fig. 2.

Immunofluorescence features of fibrillary glomerulonephritis (contributed by Dr. Alexander). Monotypic staining on fibrillary glomerulonephritis on routine immunofluorescence microscopy should prompt paraffin IF, IgG subclass, and DNAJB9 staining.

Fig. 3.

KM55 staining in primary and secondary forms of IgA nephropathy. Renal biopsy from a 28-year-old male who had previously undergone right hemicolectomy for Crohn’s disease, presenting with elevated creatinine, subnephrotic proteinuria, hematuria, and negative serologies. (A) Mesangioproliferative pattern of glomerular injury with segmental sclerosis (PAS, 200×). (B) 3+ mesangial granular staining for IgA, and (C) 3+ mesangial granular staining for KM55 (contributed by Drs. Singh and Raj).