Abstract: FR-PO0062
Isolated Proteinuria from Compound Heterozygous CUBN Variants in an Adult Athlete: A Genetics-First Teaching Case
Session Information
- ADPKD and Cystic Kidney Disease - 2
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1201 Genetic Diseases of the Kidneys: Cystic (Monogenic)
Authors
- Bitar, Mustapha K., The University of Kansas School of Medicine, Wichita, Kansas, United States
- Short, Levi, The University of Kansas School of Medicine, Wichita, Kansas, United States
Introduction
Isolated proteinuria due to CUBN variants is an uncommon but important mimic of glomerular disease. This case highlights why early genetic testing should be considered in adults with persistent proteinuria, bland urine sediment, and preserved kidney function.
Case Description
A 44-year-old male athlete with recently diagnosed hypertension was found on routine screening to have isolated proteinuria. He consumed about 75 g/day of protein supplements. Evaluation showed 1+ proteinuria, UPCR 0.39-0.42 g/g, 24-hour urine protein 1.2 g, serum creatinine 1.1 mg/dL, and cystatin C-based eGFR 80 mL/min/1.73 m2. He had no hematuria, family history of kidney disease, or end-stage kidney disease. Blood pressure was controlled on losartan 100 mg daily. Because kidney function was preserved and urine sediment was bland, biopsy was deferred despite persistent non-nephrotic proteinuria. Kidney gene panel testing identified compound heterozygous pathogenic CUBN variants: c.8071G>A (p.Gly2691Arg) and c.5733+2T>C, establishing CUBN-related benign proteinuria.
Discussion
Persistent isolated proteinuria in an otherwise healthy adult was ultimately attributed to a hereditary etiology identified through genetic testing rather than kidney biopsy. The outcomes of this approach were avoidance of invasive biopsy and unnecessary immunosuppression, continuation of renoprotective therapy, and referral for genetic counseling. Teaching points: first, genetic testing should be integrated early in the evaluation of persistent non-nephrotic proteinuria when hematuria is absent and kidney function is preserved; second, identifying CUBN-related proteinuria provides prognostic clarity and changes management; third, a genetics-first approach can shorten the diagnostic workup and reduce unnecessary procedures.