Kidney Week 2025 Annual Meeting-Renal Biopsy: Clinical Correlations 2025

Video Transcription

Video Summary

The session features renal pathologists and a clinical discussant presenting four challenging clinicopathologic kidney biopsy cases with audience Q&A, emphasizing careful morphologic interpretation, clinical correlation, and when to pursue genetic or immune-mediated diagnoses.

<strong>Case 1:</strong> A 40-year-old man with progressive CKD, subnephrotic proteinuria, bland urine, small echogenic kidneys, and extensive tubulointerstitial scarring with chronic lymphocytic interstitial nephritis plus secondary hyperfiltration-type FSGS. Biopsy was nonspecific but prompted deeper family history (multiple relatives with ESRD). Standard gene panel was negative; family testing revealed an <strong>ADTKD–MUC1</strong> mutation, highlighting that MUC1 VNTR variants can be missed by routine sequencing and may require specialized testing (e.g., snapshot PCR/long-read methods or screening pipelines with confirmatory testing). Supportive CKD care and transplant counseling were discussed; experimental therapies targeting mutant MUC1 trafficking were noted.

<strong>Case 2:</strong> A 60-year-old woman with febrile illness, AKI, proteinuria, low complements, and glomerular endocapillary hypercellularity composed largely of <strong>CD68+ histiocytes</strong>, negative immune deposits, and rare hemophagocytosis—diagnosed as <strong>histiocytic glomerulopathy</strong> associated with <strong>HLH/macrophage activation syndrome</strong>, sometimes renal-limited and occasionally overlapping with low-grade TMA. She responded to steroids with relapse requiring maintenance immunosuppression.

<strong>Case 3:</strong> A 68-year-old man with CKD and proteinuria showed focal endocapillary hypercellularity, microangiopathic endothelial injury, and striking <strong>linear IgA–lambda</strong> GBM staining without deposits on EM, consistent with <strong>monotypic atypical anti-GBM disease</strong>. Workup found MGUS with a non-matching IgG-kappa clone, underscoring uncertain pathogenesis/classification and potential post-transplant recurrence risk.

<strong>Case 4:</strong> A 41-year-old man with nephrotic syndrome and AKI had diffuse podocyte effacement with early tip-lesion FSGS and characteristic <strong>punctate IgG “dusting” colocalizing with nephrin</strong>, supporting <strong>anti-nephrin–mediated podocytopathy</strong>. Steroids/CNI improved proteinuria; rituximab and other B-cell–targeted or antibody-removal strategies were discussed as emerging therapy.

Asset Subtitle

Moderator(s): Laura Biederman, Ritu Gupta

Presentation(s):

Case 1 - Vanderlene Kung, Zainab Obaidi
Case 2 - Mercury Lin, Zainab Obaidi
Case 3 - Cathryn Lapedis, Zainab Obaidi
Case 4 - Sujal Shah, Zainab Obaidi

ASN thanks the Renal Pathology Society for assistance with this session.

Support for the Digital Pathology Room is provided by Otsuka America Pharmaceutical, Inc.

Meta Tag

Date 11/8/2025

Pathway 1 Pathology

Session ID 507223

Keywords

renal pathology

kidney biopsy cases

clinicopathologic correlation

tubulointerstitial nephritis

secondary FSGS

ADTKD-MUC1

MUC1 VNTR mutation

genetic kidney disease testing

histiocytic glomerulopathy

hemophagocytic lymphohistiocytosis (HLH)

macrophage activation syndrome

thrombotic microangiopathy overlap

atypical anti-GBM disease

linear IgA lambda GBM staining

anti-nephrin mediated podocytopathy