Because primary hyperoxaluria type 1 (PH1) is so rare, some people may have symptoms for a long time before their doctor diagnoses the disease.
People are most often diagnosed with PH1 by:
- A doctor’s examination
- Family history
- X-rays
- Genetic or lab test results
Physical Exam
Your doctor may screen for PH1 if you or your child has symptoms like:
- Kidney stones
- Blood in the urine
- High levels of calcium in the kidneys
The symptoms of PH1 can look like those of other diseases. Tests will help to rule out other causes.
Family History
Your family history may suggest a high risk for PH1, which is a genetic (inherited) disease. If you have a sibling who’s been diagnosed with it, you may want to be tested for the gene that causes it.
PH1 is caused by a mutation, or change, in the AGXT gene. This is a recessive gene. So to have the disease, you must inherit two copies of the mutation, one from each parent. Your parents may have just one copy each and show no symptoms.
PH1 is more likely in people whose parents are relatives and in cultures where marriages between relatives are common.
Lab Tests
Laboratory tests can help your doctor narrow down the causes of your symptoms.
Blood tests measure oxalate levels in the blood. Oxalate is a natural chemical that occurs in the body and in some foods. Higher levels can lead to kidney stones, as the chemical binds to calcium. It can interfere with the absorption of nutrients, too.
Urine tests may show high levels of oxalate, but this doesn’t always mean that you have PH1. High levels of a protein called glycolate in your pee also may suggest PH1. But they don't confirm the diagnosis.
Imaging tests like X-rays, CT scans, or ultrasounds can show kidney stones or calcium oxalate deposits in your tissues. Calcium oxalate, formed when oxalate combines with calcium, is what most kidney stones are made of.
X-rays may also show long-term damage to your bones that can be caused by PH1, like osteosclerosis (dense bones) or osteopenia (thinning bones). They can show changes like higher density where bone is rapidly growing, or areas where bone tissue is thinner than normal.
Biopsy, in which your doctor takes a small tissue sample to be examined at a lab, may help confirm your diagnosis or show if PH1 has spread in your body.
To diagnose PH1, you may need:
- A kidney biopsy to show oxalate deposits in tissue
- A bone marrow biopsy to show oxalate deposits in bone
- A liver biopsy, which can show if you have an enzyme shortage caused by a mutation in your AGXT gene. (Enzymes are substances that speed up chemical reactions in your body.) Because genetic testing is widely available now, it’s rare to need a liver biopsy.
Other tests you may need include:
- An eye exam to show signs of eye disease from high levels of oxalate
- An echocardiogram, which can show signs of oxalate deposits in your heart tissue
Kidney Stone Exam
Because PH1 is rare, most kidney stones are not caused by it. But if your doctor suspects you or your child have it, they can examine the kidney stones for signs that they’re caused by PH1. You might have PH1 if the stones:
- Are almost entirely made of calcium oxalate monohydrate
- Are pale in color
- Come in different shapes and sizes
Genetic Testing
A molecular genetic test can show whether you have the AGXT gene mutation and confirm the diagnosis. This test is only available through your doctor.
If you’re planning to have children and someone in your family (or your partner’s) has been diagnosed with PH1, genetic screening is important. Before you conceive, you should know your risk of passing the gene mutation to your children. See a genetics professional to be screened and counsel you when you receive the results.
If you’re pregnant and have family members with the AGXT gene mutation, you may want prenatal testing for PH1. Your doctor can do:
- Amniocentesis, where fluid that surrounds your fetus is taken and analyzed for signs of the genetic mutation
- Chorionic villus sampling (CVS), where placenta tissue is taken out and tested
People with a family history of PH1 who conceive through in vitro fertilization may be able to have a test called pre-implantation genetic diagnosis (PGD). Tissue from the embryo is tested to see if it has the AGXT gene before it’s implanted.
