Dent disease is a rare genetic kidney disorder that almost exclusively affects males, causing progressive damage to kidney structures called proximal tubules, often leading to kidney stones and eventually kidney failure in adulthood.

What Is Dent Disease

Dent disease is a chronic kidney disorder that begins with problems in structures called proximal tubules, which are the tiny tubes in the kidneys responsible for reabsorbing nutrients and minerals back into the bloodstream after they have been filtered. When these tubes do not work properly, important substances leak into the urine instead of being saved for the body to use. This leads to a cascade of problems that worsen over time, eventually threatening kidney function itself.^[1]

The disease is present from birth because it is caused by genetic changes, but symptoms usually appear during childhood. However, many individuals remain undiagnosed until adulthood, especially if their symptoms are mild or detected only by chance during routine testing. The primary feature that appears in virtually all patients is the presence of small protein molecules in the urine, known as low-molecular-weight proteinuria. Additionally, affected individuals typically have too much calcium in their urine, a condition called hypercalciuria, which can lead to calcium deposits in the kidneys and recurrent kidney stones.^[3]

Because the disease primarily affects males and is linked to the sex chromosomes, it is considered an X-linked disorder. This pattern of inheritance explains why women can carry the genetic mutation with little to no symptoms, while their sons who inherit the mutation develop the full disease. The true number of affected individuals may be higher than reported, as the disease can go unrecognized when symptoms are subtle or when its features are mistaken for other kidney conditions.^[1]

Epidemiology

Dent disease is classified as a rare condition. Around 250 affected families have been documented in medical literature, though researchers believe the actual number may be higher due to underdiagnosis. Many cases are not identified because individuals may have only mild signs and symptoms that do not prompt medical investigation. Furthermore, the features of Dent disease overlap with those of other kidney disorders, which can lead to misdiagnosis or missed diagnosis altogether.^[1]

Among the types of Dent disease, Dent disease type 1 is more common than Dent disease type 2. Specifically, mutations in the CLCN5 gene (which cause type 1) account for approximately 60 percent of all Dent disease cases, while mutations in the OCRL gene (which cause type 2) account for about 15 percent of cases. In the remaining 25 percent of cases, the genetic cause remains unknown, suggesting that additional subtypes or related genes may exist.^[1]

The disease manifests almost exclusively in males because of its X-linked inheritance pattern. Males have only one X chromosome, so a single mutated copy of the gene is enough to cause the disease. Females have two X chromosomes, so they would need mutations in both copies to develop the full condition, which is extremely unlikely. However, some female carriers do experience mild symptoms such as excess calcium in the urine and, rarely, kidney stones or moderate proteinuria due to random X-chromosome inactivation.^[2]

Causes

Dent disease is a genetic disorder, meaning it is caused by changes in specific genes that are passed down through families. The disease results from mutations in either the CLCN5 gene or the OCRL gene, both of which are located on the X chromosome. These genes provide instructions for making proteins that are essential for normal kidney function, particularly in the proximal tubules where most of the reabsorption of filtered substances takes place.^[1]

The CLCN5 gene produces a protein that acts as a chloride and hydrogen ion exchanger. This protein, called ClC-5, is a member of a family of channels and transporters that help control the movement of chloride ions across cell membranes. In the kidney’s proximal tubules, ClC-5 plays a critical role in helping cells take back proteins, minerals, and other valuable materials from the filtered fluid. When mutations disrupt the CLCN5 gene, the reabsorption process fails, causing these substances to spill into the urine instead of being returned to the bloodstream.^[4]

The OCRL gene encodes an enzyme called phosphatidylinositol bisphosphate 5-phosphatase, which is involved in processing certain fats in cell membranes. This enzyme is active throughout the body, not just in the kidneys. Mutations in the OCRL gene cause Dent disease type 2 and are also responsible for a related condition called Lowe syndrome, which has more severe symptoms affecting the eyes and brain. Scientists are still working to understand why OCRL mutations primarily affect the kidneys in Dent disease type 2, given that the enzyme is produced in many tissues.^[1]

Research suggests that when either of these genes is mutated, the ability of the proximal tubules to reabsorb filtered substances is disrupted. This leads to the characteristic features of Dent disease, including the loss of proteins and calcium in the urine, the formation of kidney stones, and the progressive decline in kidney function over time.^[5]

Risk Factors

The primary risk factor for Dent disease is having a family history of the condition. Because Dent disease is inherited in an X-linked recessive pattern, males are far more likely to develop the disease than females. If a woman is a carrier of a mutation in the CLCN5 or OCRL gene, each of her sons has a 50 percent chance of inheriting the mutation and developing the disease. Similarly, each of her daughters has a 50 percent chance of inheriting the mutation and becoming a carrier.^[7]

Males who have the disease will pass the mutated gene to all of their daughters, making them carriers, but will not pass it to their sons because fathers pass the Y chromosome, not the X chromosome, to male offspring. This pattern means that the disease typically appears in males across generations, often skipping a generation if it passes through carrier females who do not show symptoms.^[10]

In some cases, Dent disease can occur as a de novo mutation, meaning it appears for the first time in a family without any previous history of the disorder. These spontaneous mutations happen randomly during the formation of reproductive cells or early in development and are not inherited from either parent.^[7]

Female carriers of the mutation are usually asymptomatic or have very mild symptoms. However, due to a phenomenon called X-chromosome inactivation, where one of the two X chromosomes in female cells is randomly turned off, some carrier females can manifest mild features of the disease. These may include excess calcium in the urine and occasionally kidney stones or mild proteinuria. It is rare for female carriers to develop chronic kidney disease, though it has been documented in some cases.^[2]

Symptoms

The symptoms of Dent disease vary widely from person to person, even within the same family. Some individuals are only mildly affected and may not develop noticeable symptoms until adulthood, while others experience significant problems beginning in childhood. The most consistent finding in all affected males is the presence of small proteins in the urine, a condition known as low-molecular-weight proteinuria. This feature is present in 100 percent of cases, but it usually causes no symptoms and is only detected through specialized urine testing.^[7]

Another hallmark of Dent disease is hypercalciuria, which means excessive amounts of calcium are excreted in the urine. This occurs in more than 95 percent of affected individuals. Hypercalciuria can lead to the formation of calcium deposits in the kidneys, a condition called nephrocalcinosis, as well as recurrent kidney stones, known as nephrolithiasis. Patients with excess calcium in their urine may experience increased urine volume and excessive thirst as their bodies try to dilute and flush out the high calcium levels.^[5]

Kidney stones are a common and often painful complication of Dent disease. Stones can cause episodes of severe pain, known as renal colic, which is typically felt in the back, sides, and lower abdomen and may radiate down into the groin. The pain often comes in waves, building up over several minutes and then subsiding in a repeating cycle. Kidney stones may also cause blood in the urine, a condition called hematuria, which can sometimes be visible to the naked eye but is more often detected only under a microscope.^[6]

Some individuals with Dent disease develop a more severe form of proximal tubule dysfunction known as Fanconi syndrome. This syndrome involves the loss of multiple substances in the urine, including amino acids, glucose, phosphate, potassium, and bicarbonate. When phosphate levels in the blood become too low, it can lead to a bone condition called rickets in children or osteomalacia in adults. Rickets causes softening and weakening of the bones, which can result in bone pain, bowed legs, and difficulty walking. In young children, severe rickets may delay walking, cause a child to stop using a limb, or lead to crying when the child is picked up.^[5]

The progressive kidney damage caused by Dent disease often leads to chronic kidney disease and eventually end-stage renal disease (ESRD), a life-threatening condition in which the kidneys are no longer able to filter waste products and excess fluids from the body. Between 30 and 80 percent of affected males develop ESRD, typically between the ages of 30 and 50, though some individuals do not reach this stage until their sixties or later. In some cases, kidney function remains stable throughout life.^[2]

Dent disease type 2, caused by mutations in the OCRL gene, can be associated with additional symptoms beyond kidney problems. These may include mild intellectual disability, reduced muscle tone known as hypotonia, and clouding of the lens of the eye called cataracts. However, the cataracts in Dent disease type 2 are usually subclinical, meaning they do not impair vision and are only detected during an eye examination. Affected individuals may also have elevated levels of certain muscle enzymes in their blood, such as creatine phosphokinase and lactate dehydrogenase, even without noticeable muscle symptoms.^[1]

Growth restriction and short stature are also seen in some patients with Dent disease. In certain cases, human growth hormone treatment has been used to address growth failure without adversely affecting kidney function.^[2]

Prevention

Because Dent disease is a genetic condition, it cannot be prevented in the traditional sense. However, if there is a known family history of the disease, genetic counseling can help prospective parents understand the risk of passing the mutation to their children. When a mother is a known carrier of the CLCN5 or OCRL mutation, each of her children has a 50 percent chance of inheriting the gene. Male children who inherit the mutation will develop the disease, while female children who inherit it will become carriers.^[7]

For families with a known history of Dent disease, molecular genetic testing can confirm whether a mutation is present. Female relatives of affected males may choose to undergo testing to determine if they are carriers. This information can be valuable for family planning and for monitoring any mild symptoms that may develop in carrier females.^[2]

While the underlying disease cannot be prevented, steps can be taken to reduce the risk of complications and slow the progression of kidney damage. Lifestyle modifications play an important role in managing the disease. Maintaining good hydration is essential, as drinking plenty of water helps dilute the urine and reduce the concentration of calcium, making it less likely for kidney stones to form. A low-salt diet is also recommended because excess salt in the diet can increase calcium excretion in the urine.^[7]

Patients with Dent disease should be cautious about medications that can harm the kidneys. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, and aspirin should be avoided when possible, as these medications can impair kidney function. Certain antibiotics can also be harmful to the kidneys, so it is important for patients to inform their healthcare providers about their diagnosis before starting any new medication. Similarly, contrast dyes used in diagnostic imaging tests such as CT scans, MRIs, and angiograms can be toxic to the kidneys, and alternative imaging methods should be considered when feasible.^[7]

For individuals diagnosed with Dent disease, regular monitoring is crucial. Annual urine tests to measure protein and calcium levels, along with periodic blood tests to assess kidney function, can help detect worsening kidney damage early. Early identification of declining kidney function allows for timely intervention and adjustments to treatment strategies.^[2]

Pathophysiology

To understand how Dent disease disrupts normal kidney function, it is helpful to know how healthy kidneys work. Each kidney contains about one million tiny filtering units called nephrons. Each nephron consists of a filter called a glomerulus and a long tube called a tubule. Blood is continuously filtered through the glomerulus, which removes excess water, waste products, and small molecules while keeping blood cells and large proteins in the bloodstream. This filtering process produces a fluid called primary urine.^[3]

The tubules, particularly the proximal portion closest to the glomerulus, are responsible for reabsorbing valuable substances from the primary urine back into the bloodstream. These substances include water, electrolytes such as sodium, potassium, calcium, and phosphate, as well as glucose, amino acids, and small proteins. The tubules also regulate the body’s acid-base balance. This reabsorption process ensures that the body retains the nutrients and minerals it needs while excreting waste products and excess substances in the final urine.^[3]

In Dent disease, mutations in the CLCN5 or OCRL gene disrupt the normal function of the proximal tubules. The CLCN5 gene produces a protein called ClC-5, which is a chloride and hydrogen ion exchanger located in the membranes of cells in the proximal tubules. This protein is essential for creating the proper environment inside cell compartments called endosomes, which are used to transport and process the substances being reabsorbed. When ClC-5 is absent or malfunctioning, the endosomes cannot work correctly, and the reabsorption of proteins, calcium, phosphate, and other substances is impaired.^[5]

The OCRL gene produces an enzyme that processes specific fats in cell membranes. This enzyme is involved in controlling the shape and movement of cellular structures, including those involved in the reabsorption process. When the OCRL enzyme is defective, it disrupts the normal trafficking of materials within cells, leading to similar problems with reabsorption in the proximal tubules.^[1]

The failure of the proximal tubules to reabsorb small proteins results in low-molecular-weight proteinuria, the hallmark feature of Dent disease. Similarly, the inability to reabsorb calcium leads to hypercalciuria. When excessive calcium remains in the urine, it can crystallize and form calcium deposits in the kidney tissue, causing nephrocalcinosis, or clump together to form kidney stones.^[5]

Over time, the chronic presence of high calcium levels in the urine, the formation of stones and calcium deposits, and the ongoing stress on the kidneys lead to progressive kidney damage. The kidney tissue becomes scarred, and the filtering capacity of the kidneys gradually declines, eventually resulting in chronic kidney disease and, in many cases, end-stage renal disease.^[2]

In some patients, the dysfunction of the proximal tubules is more extensive, leading to a generalized loss of multiple substances in the urine. This condition, called Fanconi syndrome, results in low blood levels of phosphate, which are necessary for bone health. Low phosphate levels cause rickets or osteomalacia, bone disorders characterized by soft, weak bones that can become deformed or painful.^[5]

It remains unclear why mutations in the OCRL gene, which produces a protein that is active throughout the body, primarily affect the kidneys in Dent disease type 2. The same gene mutations can also cause Lowe syndrome, a more severe condition that affects the eyes, brain, and kidneys. Researchers believe there may be a continuum of disease severity depending on the specific mutation and how severely it affects the function of the OCRL enzyme.^[5]