CLCN5

If you have unexplained kidney problems, kidney stones that started early, or a family history of kidney failure on the male side, a standard panel may not tell you why. CLCN5 (chloride voltage-gated channel 5) testing looks at a single gene on the X chromosome that, when broken, causes a rare but under-recognized kidney condition called Dent disease type 1.

This is a genetic test, not a blood marker that rises and falls with your habits. It checks the spelling of one specific gene to see whether you carry a variant that disrupts how your kidneys reclaim small proteins, calcium, and other nutrients from the urine. The result can reframe a confusing kidney workup and change what you and your specialist do next.

What This Gene Actually Does

CLCN5 carries the instructions for a protein called ClC-5, a tiny channel inside the cells lining the kidney's filtering tubes. ClC-5 sits in small bubble-like compartments inside these cells and helps acidify them, which is how the cells grab back small proteins and minerals before they leave the body in urine.

When CLCN5 carries a damaging variant, the ClC-5 channel either does not get built correctly, gets destroyed early, or reaches its destination but cannot move chloride properly. The kidney loses its ability to reclaim small proteins (called low-molecular-weight proteinuria), and over years this is linked to stone formation, calcium deposits in the kidney, and slow loss of kidney function.

Dent Disease Type 1: The Core Condition This Test Detects

Dent disease type 1 is an X-linked condition, which means it primarily affects males who inherit one altered copy of CLCN5 from their mother. In the largest European cohort of 207 patients with Dent disease type 1, chronic kidney disease was common and the rate of progression was influenced by age and the specific genotype carried.

The condition shows up differently in different people, even within the same family. Across studies, low-molecular-weight proteinuria is nearly universal, while nephrocalcinosis (calcium deposits in the kidney) appears in roughly 60 to 70% of patients, hypercalciuria (too much calcium in urine) in 40 to 70%, and kidney stones in about 25 to 45%. Some carriers go through life with mostly normal labs while a brother with the same variant develops the full picture.

Why Standard Kidney Panels Often Miss It

Many people with CLCN5 variants are told they have a glomerular kidney disease like focal segmental glomerulosclerosis (FSGS) and are sometimes given immunosuppressive drugs they do not need. The reason is straightforward: routine panels measure mainly albumin in the urine and total kidney function, but they do not measure the small proteins that leak when ClC-5 is broken.

In one analysis of 126 proteinuric patients, a specific urine pattern flagged Dent disease type 1 with high accuracy: a distinctive combination of high low-molecular-weight protein, a low albumin-to-total-protein ratio, and high total protein together pointed strongly to the condition. CLCN5 sequencing is the confirmatory step once that pattern is detected.

Chronic Kidney Disease and Kidney Failure

In the 207-patient European cohort, chronic kidney disease and kidney failure were highly prevalent in affected males, with progression linked to both age and genotype. A separate analysis of 162 patients found that kidney stone risk and the speed of progression to kidney failure depended on how much working ClC-5 was left, meaning the type and location of the variant matters.

Some men reach end-stage kidney disease without any of the classic warning signs. Case reports describe truncating CLCN5 variants causing kidney failure in patients who had no kidney stones, no calcium deposits, and no other clues. This is why unexplained chronic kidney disease in a male, especially with any family history of kidney problems, is a reason to consider this test.

Heavy Protein Loss Without the Usual Pattern

A confusing feature of Dent disease type 1 is that many patients have very high total protein in their urine, sometimes in the nephrotic range, but their blood albumin stays normal and they do not develop the swelling typical of nephrotic syndrome. Biopsies often show scarring and glomerulosclerosis even when kidney function appears normal.

One reported variant, L521F, was linked to focal segmental glomerulosclerosis and damage to the podocytes (the cells that form the kidney's filter), suggesting CLCN5 problems are not confined to the tubules. This is one of the reasons CLCN5 testing is now considered in male patients with unexplained FSGS or heavy proteinuria with normal albumin.

Atypical Presentations Worth Knowing About

A small fraction of CLCN5 variants present in ways that look like other conditions. Some patients have isolated high urine calcium without the rest of the picture. One reported case had a Bartter-like picture with low potassium and a chemistry imbalance called metabolic alkalosis. A single-center series of 12 boys with Dent disease also reported a high frequency of asymptomatic heart rhythm abnormalities.

These atypical presentations matter because they explain why the test is sometimes ordered for unexplained pediatric proteinuria, unexplained CKD, or unusual mineral imbalances rather than only for textbook Dent disease.

Reconciling the Variability

It can feel contradictory that one brother with a CLCN5 variant develops kidney failure while another with the exact same variant has normal labs. The reason is that CLCN5 is a susceptibility gene with strong but incomplete penetrance: the variant sets up the risk, but timing, other genes, kidney stressors, and likely some chance determine whether and when the disease shows itself. A positive test is not a verdict, it is a reason to monitor more closely.

What an Out-of-Pattern Result Should Make You Do

Because CLCN5 is a single inherited DNA sequence, the result does not change over time. What changes is your interpretation and your follow-up plan. A positive result should prompt a focused workup with a nephrologist, ideally one familiar with inherited tubulopathies.

• Quantify what your kidneys are doing now: order a 24-hour urine for calcium and protein, urine alpha-1-microglobulin or beta-2-microglobulin, kidney function (creatinine and eGFR), and a kidney ultrasound to look for stones or calcium deposits.
• Screen male relatives: brothers, sons, and maternal uncles share the same X chromosome risk. Mothers are often unaffected carriers who can still pass the variant on. Cascade testing in families is recommended but underused.
• Avoid the wrong treatments: a positive CLCN5 result can spare you from immunosuppressive drugs sometimes given for misdiagnosed FSGS.
• Track kidney function over time: even with a confirmed diagnosis, the speed of progression varies widely and is the most actionable thing to monitor.

Tracking and Follow-Up

The CLCN5 result itself never needs to be retested. What needs serial tracking is what the gene predicts: kidney function, urine calcium, urine protein subtypes, and stone burden. A reasonable cadence for someone with a confirmed pathogenic variant is to repeat kidney function and urine studies at least once a year, with imaging every one to two years or sooner if symptoms appear. Children diagnosed early may need more frequent visits during growth.

For someone who tests negative but has a strong clinical suspicion, the workup should not stop there. Other genes (including OCRL, which causes Dent disease type 2, and EHHADH) can produce similar pictures, and panel-based testing or whole-exome sequencing may be the right next step.