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Urinary myoglobin-to-creatinine ratio identified as potential biomarker for chronic benign proteinuriaCould a simple urine test help diagnose a rare kidney condition?

AI-generated summary of the cited source, checked by automated accuracy review. How we work

Key Takeaway
Consider urinary myoglobin-to-creatinine ratio as a potential biomarker for PROCHOB, pending validation.

A proteomic discovery study using high-throughput aptamer-based urinary proteomics (SomaScan®) investigated patients with chronic benign proteinuria (PROCHOB) caused by biallelic pathogenic variants in CUBN. The study compared these patients to individuals with other moderate glomerular proteinuric kidney diseases, Dent disease, and healthy individuals. The primary aim was to identify a disease-specific biomarker for PROCHOB.

The main finding was the identification of urinary myoglobin as a specific biomarker. The study reports that the urinary myoglobin-to-creatinine (uMB/Cr) ratio robustly distinguishes PROCHOB from other moderate glomerular proteinuric kidney diseases and that PROCHOB can be clearly distinguished from Dent disease based on the urinary uBMG-to-creatinine ratio. The biomarker remained normal in healthy individuals and those with typical glomerular diseases with moderate proteinuria. No safety or tolerability data related to the diagnostic testing were reported.

Key limitations are not reported in the abstract, but the study type is listed as 'OTHER' and not a formal clinical trial. Crucially, the abstract does not report the sample size, effect sizes, statistical measures of diagnostic performance (e.g., sensitivity, specificity), or p-values/confidence intervals for the findings. The practice relevance is that this establishes a potential noninvasive diagnostic tool for PROCHOB, which could prompt targeted genetic testing for CUBN variants. However, the findings are preliminary and based on a discovery study; their clinical utility depends on robust external validation.

Imagine having a kidney condition that looks like many others, making it hard for doctors to pinpoint. For people with a rare, inherited disease called PROCHOB, this diagnostic puzzle is a frustrating reality. The condition is caused by specific genetic changes and leads to protein in the urine, but it can be mistaken for other kidney problems.

In a new analysis, scientists looked for a unique fingerprint in the urine of people with PROCHOB. They found that a protein called myoglobin, when measured against creatinine in a urine sample, appears to be a strong signal for this specific disease. The test seemed to clearly separate PROCHOB from other conditions that also cause moderate protein loss, like Dent disease, and myoglobin levels were normal in healthy people.

This points toward a potential future where a simple urine test could guide doctors to order the right genetic test for CUBN variants much faster. However, it's important to note this is a discovery study. The research summary does not report how many people were involved, the precise strength of the test's accuracy, or key statistical measures. More validation is needed to understand how well this biomarker would work in everyday clinical practice.

What this means for you:
A urine protein may help identify a rare kidney disease, but the finding needs more validation.

Study Details

EvidenceLevel 5
PublishedApr 2026
View Original Abstract ↓
Chronic benign proteinuria (PROCHOB), caused by biallelic pathogenic variants in CUBN, presents in childhood as isolated, asymptomatic tubular proteinuria with preserved long-term kidney function. Because its clinical presentation closely mimics early stage glomerular diseases with moderate proteinuria and without increased urinary {beta}2-microglobulin (uBMG) and 1-microglobulin, numerous patients undergo unnecessary kidney biopsies and receive angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers before genetic testing is considered. Using high-throughput aptamer-based urinary proteomics (SomaScan(R)), we identified urinary myoglobin as a disease-specific biomarker for PROCHOB. We developed and confirmed a diagnostic approach in which the urinary myoglobin-to-creatinine (uMB/Cr) ratio robustly distinguishes PROCHOB from other moderate glomerular proteinuric kidney diseases. Although certain cases of Dent disease causing megalin dysfunction exhibit increased urinary myoglobin levels, PROCHOB and Dent disease can be clearly distinguished based on the uBMG-to creatinine ratio. This biomarker reflects impaired proximal tubular protein reabsorption because of cubilin dysfunction and remains normal in healthy individuals or those with typical glomerular diseases with moderate proteinuria. Our findings establish a noninvasive diagnostic tool for PROCHOB that prompts targeted genetic testing for CUBN variants using the uMB/Cr and urinary uBMG-to-creatinine ratios. This strategy has the potential to transform the clinical diagnostic pathway for isolated proteinuria.
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