CLCN5 Genotype

If you or a male relative has unexplained protein in the urine, kidney stones, or early kidney decline that no standard workup has explained, this test asks a specific question: is the cause a single inherited change in a gene called CLCN5 (chloride voltage-gated channel 5)?

A change in this gene causes Dent disease type 1, a rare kidney condition that often goes undiagnosed for years because it can look like more common diseases on a standard panel. Knowing your genotype reframes the entire workup and pulls family members into the conversation.

What This Test Actually Looks At

CLCN5 sits on the X chromosome and provides the blueprint for a protein called ClC-5. Despite the historical "channel" label in its name, ClC-5 actually works as a chloride/proton exchanger, swapping chloride for hydrogen ions across membranes. It lives inside tiny compartments called endosomes within the cells of the kidney's reabsorbing tubes (the proximal tubules). There, it helps keep the inside of those compartments acidic, which is what allows these cells to take small proteins back out of the urine before they are lost. When the gene is broken, that reabsorption process fails, proteins leak through, and over years the kidneys can scar and weaken.

The test reads the DNA sequence of this gene and reports whether you carry a variant known to disrupt the transporter. Because the gene is on the X chromosome, men, who carry only one copy, are usually fully affected, while women who carry one copy may have milder or no symptoms.

Dent Disease Type 1

The clearest reason to test CLCN5 is to confirm or rule out Dent disease type 1. This condition shows up most often as heavy leakage of small proteins in the urine (called low-molecular-weight proteinuria), high calcium in the urine, calcium deposits in the kidney, kidney stones, and gradual loss of kidney function over years.

In a European study of 207 patients, low-molecular-weight proteinuria was present in essentially everyone with confirmed Dent disease type 1, calcium deposits in the kidney appeared in about 66 percent, high urine calcium in roughly 44 percent overall (around 73 percent in children versus 19 percent in adults), and kidney stones in about 26 percent of patients. The same study found that men with this diagnosis frequently progress to chronic kidney disease, with the rate of decline shaped by both age and the specific genetic change.

What this means for you: if you have been told you have unexplained low-molecular-weight proteinuria or your urine workup keeps coming back with a tubular pattern, this gene is one of the few that can actually explain the picture.

Chronic Kidney Disease Without the Classic Picture

A growing number of reports show that some men with a damaging CLCN5 variant never show the full Dent disease picture. They simply have chronic kidney disease or, in some cases, end-stage kidney disease of unclear cause.

Two brothers carrying the same disrupting variant in CLCN5 have been described in which one developed Dent disease and the other had normal labs and no symptoms, illustrating how unpredictable the inherited risk can be. Other case reports document end-stage kidney disease in men with a CLCN5 variant but no classic tubular signs at all. If you have unexplained kidney failure in your family and no answer from standard workups, this gene belongs on the differential.

Misdiagnosis as Glomerular Disease

One of the most clinically important findings is that Dent disease can look like primary glomerular diseases such as focal segmental glomerulosclerosis (FSGS, a pattern of scarring in the kidney's filters). Patients can have heavy protein in the urine without the swelling or low blood albumin that usually accompanies primary glomerular disease.

A novel CLCN5 variant has been reported in a family with FSGS and direct injury to the kidney's filtering cells, suggesting CLCN5 may sometimes cause this scarring pattern as a primary event rather than as a downstream consequence of tubular damage. The practical takeaway is straightforward: if you have been labeled with FSGS or unexplained heavy proteinuria, especially as a male, knowing your CLCN5 status can change the diagnosis and prevent unnecessary immune-suppressing treatment.

Kidney Stones and High Urine Calcium

Carriers of certain CLCN5 changes can show high calcium in the urine even without the full Dent picture. In a study of patients with hypercalciuria, inactivation of CLCN5 was shown to cause isolated high urine calcium in some individuals, though such variants were not a common cause of typical idiopathic hypercalciuria. If recurrent calcium stones run in your male line, this is worth knowing.

How Different Variants Shape the Picture

Hundreds of disruptive changes have been catalogued across this gene, with a recent 2026 database identifying more than 500 unique pathogenic or likely pathogenic variants. Roughly a third are missense or in-frame changes, about a third are frameshift changes, around 14 to 28 percent are nonsense changes, around 10 to 13 percent affect how the gene is spliced, and the rest are larger deletions or rarer events. Some variants cause the protein to misfold and get destroyed inside the cell. Others let the protein reach the right location but reduce how well it works.

A study of 162 patients suggested that the type and location of the change may matter, with some evidence that kidney stone risk and progression to kidney failure track with how much residual function the transporter keeps. Other large cohorts, however, have found no clear genotype-phenotype correlation, and even within the same family carrying the same variant the severity can differ widely. A positive test result is the start of a personalized monitoring plan, not a fixed prediction.

What a One-Time Genetic Result Means Long Term

This is a one-time test. Your DNA does not change, so the genotype you get today is the genotype you will carry for life. There is no benefit to repeating the same panel later unless a variant of uncertain meaning needs confirmation by a different sequencing method.

The value of the result comes from what you do with it over the years that follow. If you carry a disrupting CLCN5 variant, the smart move is consistent monitoring of the kidney itself: regular urine protein measurements that include small proteins (such as alpha-1 microglobulin), urine calcium, kidney function (creatinine and cystatin C with calculated filtration rate), and periodic imaging if stones or calcium deposits have been seen. Get a baseline once you know your genotype, retest kidney markers in three to six months if you are starting any new treatment, and at least annually after that.

What to Do With an Unexpected Result

If your test returns a clearly damaging CLCN5 variant, the next step is not another genetic test. It is a structured kidney workup: a urine collection that measures small proteins and calcium, blood work including kidney function and electrolytes, and kidney imaging to look for stones or calcium deposits. A nephrologist who has seen Dent disease before should be involved in interpreting the combined picture.

A referral to a genetic counselor is appropriate before and after testing, especially because results matter for biological relatives. Sons of a female carrier have a 50 percent chance of inheriting the variant, and daughters of an affected man will all be carriers. Cascade testing of male relatives often uncovers additional family members who have been quietly losing kidney function without an explanation.

When Results Can Be Misleading

Genetic testing has its own kinds of confounders that have nothing to do with food, time of day, or recent activity. A few to keep in mind:

• Panel coverage: the test only detects the specific changes it is designed to find. A negative result does not rule out a rare variant in the same gene that the panel does not cover.
• Variant of uncertain meaning: sequencing sometimes flags a change whose clinical impact is unknown. This is not the same as a positive result, and it should be interpreted by a specialist alongside your clinical picture.
• Carrier status in women: because the gene is on the X chromosome, female carriers may have normal kidney markers or only mild changes. A normal urine workup in a woman does not rule out that she carries the variant.
• Incomplete penetrance: two relatives with the same variant can have very different outcomes, as documented in published family reports. A positive result tells you the inherited risk is present; it does not guarantee the disease will develop.

Why a Standard Lab Panel Is Not Enough

A typical kidney panel measures total protein and albumin in the urine and overall filtration. None of these reliably detects the leakage of small proteins that defines Dent disease. People with this condition can have heavy total proteinuria that gets labeled as glomerular disease on a standard report, when the real cause is at the level of the kidney's reabsorbing cells.

If you suspect Dent disease, the standard panel needs to be paired with a specialized urine test for small proteins (such as alpha-1 microglobulin) and, if that pattern is found, with this genetic test. One published cohort identified an alpha-1 microglobulin to creatinine ratio of 120 mg/g or higher together with an albumin to total protein ratio of about 0.21 or lower as the urine pattern that should prompt CLCN5 sequencing.