Actor portrayal
Frequently asked questions
Get answers to some of the most common questions that people with primary hyperoxaluria (PH) and in the broader community have about this rare disease.
Questions about PH
Hyperoxaluria is a condition in which there is too much oxalate in a person’s urine. (Hyper means too much, oxal stands for oxalate, and uria stands for urine.)
Hyperoxaluria can have different causes. Primary hyperoxaluria has a genetic cause. A version called secondary hyperoxaluria can be caused by excess oxalate from the diet or gastrointestinal disease.
Primary hyperoxaluria, or PH, is a family of rare genetic disorders in which the liver produces too much oxalate, which can then cause kidney stones, kidney damage, and, in some cases, damage to other organs.
The 3 known subtypes of PH are PH1, PH2, and PH3. Each subtype is linked to mutations in a specific gene. When these genes are mutated, they either can’t make enzymes or they make enzymes that don’t work correctly.
- PH1 is caused by missing or malfunctioning AGT enzymes
- PH2 is caused by missing or malfunctioning GRHPR enzyme
- PH3 is caused by missing or malfunctioning HOGA enzymes
A rare disease is a disease affecting fewer than 200,000 people in the United States.
Primary hyperoxaluria is a rare disease that is estimated to affect approximately 8,500 people in the United States, many of whom may still be undiagnosed.
Studies of reported cases of PH suggest that fewer than 3 in 1 million people (or up to 1,000 people in the United States) have PH. However, one study that analyzed a large genetic database to see how many people had genetic mutations that cause PH estimated that more than approximately 1 in 39 thousand people (or approximately 8,500 people) in the United States may have PH. This includes both people who have been given a diagnosis and people who have not yet been given a diagnosis.
Yes, in some people. As PH progresses, calcium oxalate deposits build up in the kidneys, causing kidney damage and, in severe cases, kidney failure. When the kidney can no longer filter oxalate adequately, systemic oxalosis may occur. When this happens, calcium oxalate crystals start to collect in other organs throughout the body, causing damage to the heart, bones, retina, and skin. If PH is diagnosed and treatments are started early, these treatments may help to manage symptoms and slow down the progression of PH.
Oxalate is a waste product found in plants and humans. It’s not a required nutrient and has no known function in humans. Oxalate cannot be degraded in humans and is usually filtered out by the kidneys, leaving the body in the urine. When the kidneys fail to filter out enough oxalate, it can build up to toxic levels, causing kidney stones and kidney damage.
As the kidneys become more and more damaged, they lose their ability to adequately filter substances that are harmful to the human body. When this happens, calcium oxalate crystals start to deposit in other tissues such as the heart, bones, retina, and skin. This complication is referred to as systemic oxalosis.
If you have PH, the likelihood of your child having PH depends on whether your partner has or is a carrier for the same subtype of PH that you have.
If you have PH and your partner also has the same subtype of PH (PH1, PH2, or PH3) that you do, all of your children will have PH.
If you have PH and your partner is a carrier of one of the mutated genes that cause PH, you have a 50% chance of having a child with PH and a 50% chance of having a child who is a carrier of one of the mutated genes that cause PH.
If you have PH and your partner does not have PH and is not a carrier, then your children will not have PH. However, all of your children will be carriers of one of the mutated genes that cause PH.
If neither you nor your partner have PH, but your child does, then you are both likely carriers for the mutated gene that causes one of the PH types. If you are both carriers, there is a 25% chance that your next child could have PH.
Although damage to most vital organs is reversible, damage to the kidneys, which often occurs in PH, is generally irreversible. This is why early diagnosis and early treatment are extremely important to help manage kidney health.
The ClinicalTrials.gov website provides information about clinical research studies for patients, their families and caregivers, healthcare providers, and the public. Learn more about participating in a clinical trial by visiting Clinicaltrials.gov. Enter “primary hyperoxaluria” in the “condition or disease” box and click “search.”
The Oxalosis and Hyperoxaluria Foundation, a patient advocacy organization, also has information on clinical trials available here.
You can find helpful definitions for many common PH terms and acronyms on our glossary page.
Questions about diagnosing PH
The following conditions may be associated with frequent kidney stones:
- A diet high in oxalate
- Inflammatory bowel diseases such as celiac disease, Crohn’s disease, cystic fibrosis, or short bowel syndrome
- Gastric bypass surgery
- Rare inherited disorders such as primary hyperoxaluria, cystinuria, Dent disease, adenine phosphoribosyltransferase deficiency, and familial hypomagnesemia with hypercalciuria and nephrocalcinosis
- Hypercalciuria (high levels of calcium in the urine)
One or a combination of the following can be signs or symptoms of PH. If you feel you have any of these symptoms, contact your healthcare provider.
- Family history of kidney or bladder stones
- A single kidney stone in a child
- Repeated kidney stones, multiple kidney stones at the same time
- Abnormally high levels of oxalate in your urine
- Nephrocalcinosis
- Chronic kidney disease (CKD) with no known cause
- Unexplained problems with the bones, skin, heart, or eyes, which could be signs of systemic oxalosis
The age when PH symptoms begin to appear can vary from person to person.
The symptoms of PH often appear during childhood, but sometimes the first signs of PH show up when people are adults. Even if a person experienced symptoms of PH as a child, they could go many years before getting an accurate diagnosis.
"A lot of [the doctors] still didn’t believe the diagnosis, even though I had evidence because apparently most nephrologists believe it’s a kid-borne disease or you have to have it as a kid in order for it to happen.”
– Diagnosed with PH1 at age 48
Yes. Because PH is a rare genetic disorder, most healthcare providers have never encountered a person with PH before. Nephrologists and urologists are specialists who treat kidney- and urinary tract-related issues and can help you get a diagnosis, but because of the rarity of PH, they may think first about more common causes for your condition. If you think your symptoms are suggestive of PH, don’t be afraid to ask your healthcare provider about genetic testing.
Systemic oxalosis occurs when calcium oxalate crystals start to deposit in tissues other than the kidneys. It happens when the kidneys are severely damaged and are unable to adequately filter out the calcium oxalate.
Because systemic oxalosis can affect many different parts of the body, depending on where the calcium oxalate is depositing, there are many possible signs, including repeated fractures, bone deformations, anemia, severe bone pain, poor growth, skin ulcers, a heart condition called cardiomyopathy, visual impairment, or vision loss.
The age at which people are diagnosed can vary a lot. Most people with PH are diagnosed in childhood. Some may be diagnosed as infants (infantile oxalosis), while others aren't diagnosed until they are adults.
Questions about managing PH
To monitor how well your PH is being managed, your healthcare team may test your oxalate levels, run blood tests to check your kidney health, and use imaging tests to monitor new stone formation.
Most people with PH can have their oxalate levels checked with a 24-hour urine test or urine spot test (in young children). Those who have extensive kidney damage will need a blood test to measure oxalate levels.
Kidney health is often monitored with a blood test that measures your kidney’s eGFR, or how well your kidneys are doing their job of filtering your blood.
Imaging tests can monitor for new stone formations.
In people with primary hyperoxaluria, food isn’t the main source of high oxalate; rather, toxic levels of oxalate are caused by missing enzymes.
Limiting the consumption of foods that contain high amounts of oxalate may have a small effect on reducing oxalate levels. To be safe, foods that are high in oxalate should be eaten in moderation, including the following:
- Beets
- Chocolate
- Miso
- Nuts
- Peanuts
- Potatoes
- Raspberries
- Rhubarb
- Spinach
- Sweet potatoes
- Swiss chard
- Wheat bran
Be sure to have a conversation with your healthcare provider about if and what diet modifications are needed.
Want more information about how to follow a low-oxalate diet? The University of Chicago is a great resource.
Not necessarily. While kidney stones are an indicator of high calcium oxalate levels, they aren’t the only sign. Presence of nephrocalcinosis, kidney damage, or problems in other organs are also signs of elevated oxalate.
Not necessarily. While kidney stones are an indicator of high calcium oxalate levels, they aren’t the only sign.
As primary hyperoxaluria progresses, calcium oxalate continues to build up in your kidneys, causing damage and lowering the ability to filter out wastes. This damage can occur without obvious symptoms.
Some specialists that may be part of your healthcare team are nephrologists, urologists, and genetic counselors.
Nephrologists specialize in kidney health and diseases that affect the kidneys.
Urologists specialize in treating disorders of the urinary tract, including kidney stone treatment and kidney stone removal surgeries.
If your current care team does not include these specialists, consider asking your healthcare provider whether you should schedule an appointment with a specialist.
Your eGFR, or estimated glomerular filtration rate, is a measurement of how well or poorly your kidneys are doing at filtering wastes from your blood. Your healthcare provider can identify your kidney disease stage based on your eGFR.
Questions about treating PH
Check out our Managing PH page to learn more.
Some of the most common methods used to manage oxalate levels and inhibit crystal formation include the following:
- Drinking lots of water (sometimes called hyperhydration)
- Taking crystal inhibitors, which help prevent kidney stones from forming
- Vitamin B6 for certain people with PH1 (this comes in pill form)
In addition to these management options, an RNAi therapy is approved for PH1.
RNAi therapy, also called RNA interference therapy, is a treatment that interferes with messenger RNA, the chemical messengers in your cells that give instructions for making proteins. By interfering with messenger RNA, RNAi treatments prevent these proteins from being made.
An RNAi therapy for PH1 has been approved by the US Food and Drug Administration. RNAi therapy is also being investigated in PH2 and PH3.
Vitamin B6 helps only certain people with PH1 who have specific genetic mutations. If you have PH2 or PH3, vitamin B6 may not be effective.
Dialysis is a procedure that filters waste products, like oxalate, from the blood when the kidneys cannot. For people with primary hyperoxaluria whose kidneys are severely damaged, dialysis may also be used to reduce levels of oxalate in the blood to help prevent systemic oxalosis.
Check out our Managing PH page to learn more.
Check out our Managing PH page to learn more.
Check out our Managing PH page to learn more.
Questions about PH resources
There are a number of groups and organizations that provide resources and educational materials for PH.
Here are some resources that will help you learn more about PH signs and symptoms, causes, diagnosis, and therapies:
- Oxalosis and Hyperoxaluria Foundation
- Genetic and Rare Disease Information Center: Information on PH1, PH2, PH3
- Mayo Clinic
- MedlinePlus
- Orphanet
- RareRenal
The following organizations provide education about PH and resources for people with PH and caregivers:
There are also private Facebook support groups for people with PH and their caregivers—be sure to look for these!
Explore more support for people with PH and their caregivers.
Yes. Your child qualifies for accommodations through a 504 plan.
A 504 plan requires any US school that receives federal funding to accommodate the needs of any child with a physical or a mental impairment that affects major life activities. For children with PH, accommodations may include excused bathroom breaks or trips to the drinking fountain.
Get updates
Get email updates on PH treatments and news. You can also receive resources that may help you or your loved one manage PH.
