Primary Hyperoxaluria Type 1

Primary hyperoxaluria [hi-pur-ox-uh-LU-ree-uh] type 1 (PH1) is a rare and serious condition that mainly affects the kidneys, bladder, or urinary tract. Primary refers to being born with the condition. Hyperoxaluria means having high levels of oxalates in the urine.

Oxalate is a substance that is found in many foods, including plant and animal products. It is also a waste product made naturally by your body. Your kidneys filter oxalate out of the blood and into the urine. People living with PH1 have very high levels of oxalate in their urine. This increases the risk of calcium oxalate stones (a type of kidney stone) in the kidney and/or bladder. In more serious cases or without treatment, high levels of oxalate can cause kidney failure and even harm other parts of the body.

The symptoms of PH1 are different for everyone and can begin at any time of life. Most people with PH1 develop symptoms as a child or young adult. Some of the most common symptoms include:

• Having kidney stones often
• Sharp pain in your back, side, or groin area
• Blood in the urine (pee)
• Frequent urinary tract infections (UTIs)
• Painful urination (pain when peeing)
• Urinary incontinence (loss of bladder control or bed-wetting)
• Needing to pee often
• Not able to pee or peeing in small amounts

PH1 symptoms can start as early as babies less than 1 year old. In these more severe cases, you may notice your baby is very weak and/or too small in height and weight (also known as “failure to thrive”) or shows signs of kidney failure.

PH1 is a genetic condition. So, it is passed from parent to child.

In PH1, there is a variant (change) in your AGXT (alanine-glyoxylate aminotransferase) gene. This gene provides instructions for making a substance that helps break down waste products like oxalate in your liver. People living with PH1 either make less of this important substance or don’t make it at all. This causes high levels of oxalate in the blood and urine, leading to kidney stones, kidney failure, and other complications.

More specifically, PH1 is considered an “autosomal recessive” condition. This means both parents must either have the condition or have one AGXT gene variant and pass it on to the child to cause PH1. So, PH1 is not very common.

PH1 is one of three types of primary hyperoxaluria (PH). All three types are caused by gene variants (changes) that increase oxalate levels in your body by slowing down or stopping your liver from breaking it down. The main difference is which gene has these changes, which leads to different levels of disease and symptom severity.

Early diagnosis is very important so that treatment can be started as soon as possible, especially for babies and children who show symptoms. High levels of oxalate in the blood and/or urine can combine with calcium and cause calcium oxalate stones. These are a type of “kidney stone” or “bladder stone.

The calcium oxalate stones can form in the blood vessels of your kidneys making it harder for blood to pass through and get filtered (also known as decreased kidney function). Over time, this decreased kidney function causes more oxalate to build up in your blood leading to even more stones forming in the kidneys. Without treatment, this cycle of damage can lead to kidney failure for most people living with PH1.

In very severe cases, these stones can form in other parts of your body such as your bones and other blood vessels (also known as “systemic oxalosis”).

Healthcare professionals will start with reviewing your medical history, family history and symptoms to diagnose PH1. They will likely also do a physical exam and test your blood and urine. Getting the right diagnosis is important since each PH type comes with a different level of severity and risk for complications.

Screening for hyperoxaluria is important for the following situations:

• Babies and children after their first kidney stone
• Adults who have calcium oxalate stones often
• Before a baby is born if there is a concern for PH (also known as “prenatal testing”)
• You have a family history of stone disease at any age
• Close relatives of a person who is newly diagnosed with PH

Tests

Examples of the types of tests your healthcare professional may do if they suspect PH1, include:

• Blood or saliva (spit) test for AGXT, GRHPR, and/or HOGA1 genes
• Ultrasound, CT scan, or other type of medical imaging
• 24-hour urine collection
• Analysis of the stones found in your urine
• Estimated glomerular filtration rate (eGFR)
• Oxalate level in your blood
• Kidney biopsy and/or liver biopsy (a small piece of your kidney and/or liver is removed and looked at with a microscope)

Overview

The goal of treatment for PH1 is to stop oxalate from building up in your kidneys and blood vessels. This can also help keep your kidneys healthy for as long as possible. The right treatment approach for you depends on many factors, including how severe your case is and whether you have other health conditions. So, work closely with your healthcare team to make sure your treatment plan is working for you.

Fluids

All people living with PH1 need to remember to drink enough fluids each day. Fluids are anything that turns into liquid at room temperature. While water is the most preferred, this also includes products like ice, soups/stews, gelatin, ice cream, and drinks.

Adults living with PH1 usually need at least 3 liters of fluid each day, spread out throughout the day. This helps keep the oxalate flowing out of your body and lowers the risk of forming a stone. Some people living with advanced stages of chronic kidney disease or heart failure may need to limit their fluids. In this case, talk with your healthcare professional about how much fluid is right for you.

Infants and children living with PH1 also need to drink enough fluids each day, but usually not as much as adults.

Pyridoxine (Vitamin B6)

About 30% of people living with PH1 may be able to lower their blood oxalate levels with the help of pyridoxine (vitamin B6). This treatment is available without a prescription at most pharmacies. When used for PH1, the dose is much higher than what is recommended on the product labeling. So, ask your healthcare professional if vitamin B6 might be helpful and what the recommended dose would be for you.

Everyone living with PH1 should try pyridoxine (vitamin B6) when they are first diagnosed for at least 3 months to see if it helps. However, it does not always work for everyone.

Prescription medications

Two medications are available for people living with PH1 to lower the amount of oxalate naturally made by your liver:

• Lumasiran (Oxlumo)
• Nedosiran (Rivfloza)

Both are given as an injection under the skin (“subcutaneous” or “sub-Q”) and require a prescription from your healthcare professional.

Citrate or bicarbonate salts

Urine that has too much acid increases the risk of oxalate combining with calcium to form a kidney stone and/or block the blood vessels in your kidneys. So, citrate or bicarbonate salts help lower the acidity in your urine and prevent complications from PH1. Examples include potassium citrate, potassium bicarbonate, sodium citrate, and sodium bicarbonate.

Avoid high amounts of vitamin C

It is important to avoid high amounts of vitamin C if you have PH1. This includes any vitamin C found in your diet and in any supplements or herbal products you may be taking. Vitamin C can be used by your body to make oxalate. So, getting too much vitamin C increases your risk of raising your oxalate levels and forming a kidney stone and/or blocking the blood vessels in your kidneys.

Foods high in oxalate

For people living with PH1, the amount of oxalate coming from what your body naturally makes and cannot break down is much higher than the amount coming from your food. So, lowering the amount of oxalate in your food usually does not make a big difference in lowering the risk of forming stones. For some people, it may still be helpful.

If you choose to lower oxalates in your food, some foods that are highest in oxalate include: nuts, plums, chocolate, beets, strawberries, rhubarb, sweet potatoes, tofu, and spinach. Instead of eating less of these generally healthy foods, consider eating and/or drinking calcium-rich foods at the same time. This lets the calcium and oxalate bind in your stomach and intestines instead of your kidneys.

Dialysis and transplantation

Many people with PH1 develop kidney failure. When this happens, dialysis is used to help filter the blood since the kidneys are no longer able to do so. In PH1, traditional dialysis methods cannot always keep up with how fast the body produces oxalate. So, different settings or methods may be needed to filter your blood and keep your oxalate levels down.

Kidney transplantation is another treatment option for people living with PH1 and advanced stages of chronic kidney disease (stage 4 or 5 CKD). Because the liver is responsible for helping breakdown oxalate, a liver transplant can also be helpful for PH1. The best transplant strategy is based on many factors and is different for everybody. Some approaches include:

• Liver transplant first, well before kidney failure develops
• Liver transplant followed shortly after with a kidney transplant
• Both liver and kidney transplants done at the same time
• Kidney transplant only
• Liver transplant only

Talk with your healthcare professional about which approach may be best for your specific case.

Coping with PH1

Living with PH1 can be physically and emotionally challenging for you and/or a loved one. It is very common to feel sad, scared, frustrated, or angry about living with PH1. You may also find that your emotions and feelings can change throughout the course of your disease. It is important to realize that any illness or disease can affect your mental health.

Living with a chronic disorder like PH1, can create stress. Managing stress is important for your physical and emotional wellbeing. Stress is a part of life, but too much stress can contribute to poor health.

Finding support

Having people to turn to for support can be a great help while living with or caring for a person living with PH1. Don't be afraid to tell others what you are feeling and to ask for help and support when needed. Different kinds of people can help provide and offer emotional support. Among those who can be a part of your support system include:

• Family and friends
• People also living with PH1
• A spouse or significant other
• Mentors and co-workers
• Members of your healthcare team
• Social, religious, and spiritual groups

You can ask a member of your healthcare team about getting help from a social worker. Nephrology social workers are trained in kidney disease counseling to help patients and their families cope with their disease and changes in the family, home, workplace, and community. They can help identify sources of emotional support for patients who are in need. They also identify services within federal, state and community agencies to help meet your needs and help your access services when necessary.

Questions to ask

• How likely are my (or my child’s) symptoms to be caused by primary hyperoxaluria type 1 (PH1)?
• Should I complete genetic testing to see if that may be contributing to my kidney stones? If so, do you know how I can access this testing?
• Based on my (or my child’s) symptoms and history, what test(s) would you recommend first to check for PH1?
• How many fluids should I (or my child) plan to take in each day?
• Should I (or my child) try using pyridoxine (vitamin B6) to help with my PH1? If so, what is the recommended dose for me (my child)?
• Do you recommend I use citrate or bicarbonate salt to lower the acid level of my urine? If so, does it matter which one?

• National Institutes of Health (NIH) Genetic and Rare Diseases Information Center

This content is provided for informational use only and is not intended as medical advice or as a substitute for the medical advice of a healthcare professional.