Xanthinuria
What is Xanthinuria?
Xanthinuria is a rare genetic condition that affects how your body processes certain compounds called purines. In healthy people, an enzyme called xanthine oxidase converts xanthine into uric acid. People with xanthinuria lack this enzyme or have very little of it.
Without enough xanthine oxidase, your body cannot make normal amounts of uric acid. This causes uric acid levels in your blood to become extremely low. At the same time, xanthine builds up in your body. Your kidneys filter out this excess xanthine, which can form crystals and stones in your urinary tract.
Most people with xanthinuria live normal lives without symptoms. However, some develop kidney stones made of xanthine crystals. These stones can cause pain and kidney problems if left untreated. The condition is present from birth and runs in families.
Symptoms
- Kidney stones that cause back or side pain
- Blood in the urine
- Painful urination
- Frequent urinary tract infections
- Nausea or vomiting during stone episodes
- Cloudy or dark urine
- Muscle pain or weakness in rare cases
Many people with xanthinuria have no symptoms at all. The condition is often discovered by accident during routine blood work that shows unusually low uric acid levels.
Concerned about Xanthinuria? Check your levels.
Screen for 1,200+ health conditions
Causes and risk factors
Xanthinuria is caused by genetic mutations that affect the xanthine oxidase enzyme. Type 1 xanthinuria involves a mutation in the XDH gene. Type 2 involves mutations in the MOCOS gene, which affects multiple enzymes. Both types follow an autosomal recessive pattern, meaning you must inherit one mutated gene from each parent to develop the condition.
Risk factors include having parents who carry the gene mutation and having ancestry from populations where the condition is more common. The condition affects men and women equally. You cannot prevent xanthinuria because it is determined by your genes before birth. However, knowing your family health history helps identify risk early.
How it's diagnosed
Xanthinuria is diagnosed through blood tests that measure uric acid levels. People with this condition have extremely low serum uric acid, typically less than 1 mg/dL. Normal uric acid levels range from 3.5 to 7.2 mg/dL in men and 2.6 to 6.0 mg/dL in women. Markedly low levels suggest a problem with xanthine oxidase.
Rite Aid offers uric acid testing as part of our flagship panel. If your results show very low uric acid, your doctor may order additional urine tests to measure xanthine levels. Genetic testing can confirm the specific type of xanthinuria. Imaging tests like ultrasound or CT scans can check for kidney stones.
Treatment options
- Drink plenty of water throughout the day to prevent stone formation
- Aim for at least 8 to 10 glasses of water daily
- Limit foods high in purines like organ meats, anchovies, and sardines
- Reduce intake of red meat and shellfish
- Eat more fruits, vegetables, and whole grains
- Take allopurinol medication to help prevent stone formation in some cases
- Use potassium citrate supplements to make urine less acidic
- Monitor kidney function regularly with blood tests
- Work with a urologist if kidney stones develop
- Consider lithotripsy or surgery for large or painful stones
Concerned about Xanthinuria? Get tested at Rite Aid.
- Simple blood draw at your nearest lab
- Results in days, not weeks
- Share results with your doctor
Frequently asked questions
The most common symptom is kidney stones, which can cause back pain, blood in urine, and painful urination. However, many people with xanthinuria never develop symptoms. The condition is often discovered when routine blood work shows unusually low uric acid levels.
Xanthinuria is very rare, affecting fewer than 1 in 69,000 people worldwide. The exact number is unknown because many cases go undiagnosed. People without symptoms may never know they have the condition unless blood tests reveal very low uric acid levels.
There is no cure for xanthinuria because it is a genetic condition. However, most people manage it well with lifestyle changes. Drinking plenty of water and limiting high-purine foods helps prevent kidney stones. Medications can also reduce the risk of complications.
Low uric acid in xanthinuria means your body cannot convert xanthine into uric acid properly. Levels typically drop below 1 mg/dL, compared to normal levels of 2.6 to 7.2 mg/dL. This happens because the xanthine oxidase enzyme is missing or not working correctly.
Xanthinuria causes very low uric acid levels, while gout causes high uric acid levels. Gout leads to painful joint inflammation from uric acid crystals. Xanthinuria leads to kidney stones from xanthine crystals. The two conditions are essentially opposite metabolic problems.
You do not need to avoid all purines, but limiting high-purine foods helps reduce xanthine buildup. Focus on reducing organ meats, anchovies, sardines, and excessive red meat. A balanced diet with moderate protein intake is usually sufficient. Talk to a dietitian for personalized guidance.
Most doctors recommend testing uric acid levels at least once or twice per year. Regular monitoring helps track the condition and catch any changes early. Rite Aid offers convenient testing at Quest Diagnostics locations. Your doctor may suggest more frequent testing if you develop symptoms.
Xanthinuria can cause kidney damage if xanthine stones form and block urine flow. Repeated kidney stones may lead to scarring or reduced kidney function over time. However, most people avoid serious damage by drinking plenty of water and managing stone risk. Regular monitoring helps protect your kidneys.
Yes, xanthinuria follows an autosomal recessive pattern. This means you must inherit one mutated gene from each parent to develop the condition. Parents who carry one copy usually have no symptoms. If both parents are carriers, each child has a 25% chance of having xanthinuria.
Very low uric acid may indicate xanthinuria or other rare conditions. Talk to your doctor about your results and family health history. Additional urine tests can measure xanthine levels. Even if you have no symptoms, regular monitoring helps catch potential kidney stones early.