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PH1, PH2, and PH3, the 3 known primary hyperoxaluria (PH) subtypes, are caused by missing or malfunctioning enzymes
Each of the 3 known PH subtypes is caused by a genetic mutation that keeps the liver from making a specific enzyme.
PH1
Caused by genetic mutation resulting in missing or malfunctioning
PH2
Caused by genetic mutation resulting in missing or malfunctioning
PH3
Caused by genetic mutation resulting in missing or malfunctioning
Why are these missing enzymes a problem?
When one of these enzymes is missing or malfunctioning, it causes glyoxylate to build up in the liver.
Another liver enzyme called lactate dehydrogenase (LDH) converts this glyoxylate into excessive levels of oxalate.
Why is extra oxalate a problem?
All this extra oxalate makes its way to the kidneys, where it combines with calcium, creating calcium oxalate crystals. These crystals build up in the kidneys, causing damage and kidney stones.
PH subtypes, symptom onset, and disease progression
PH1 can show up at different ages and with different levels of severity.
PH1 can appear in some infants as a severe infantile form, with severe kidney damage and poor weight gain or growth rate (also described as “failure to thrive”), before they reach the age of 1 year.
In most cases, kidney stones and other signs of PH1 first appear during childhood or early teen years. Symptoms first show up between the ages of 0.7 years and 9 years in the majority of people with PH1.
In other cases, signs of PH1 may not appear until adulthood, and have even been reported to first appear in people as old as 66 years. PH1 can show up in adults in a mild form, with recurrent kidney stones, or in a more severe form, with end-stage kidney disease.
Some people do not develop chronic kidney disease.
~24% to 41% of people with PH1 may reach kidney failure by the age of 20 years
57% of people with PH1 may reach kidney failure by the age of 40 years
Most people with PH1 will need at least 1 kidney stone removal procedure
People with PH1 will need, on average, about 3 kidney stone removal procedures during their lifetime (but this number can vary a lot from person to person)
Symptoms of PH2 can show up at different ages.
Most people show the first signs and symptoms of PH2, including kidney stones, between the ages of 1 and 11 years
Some people show their first symptoms of PH2 when they are teenagers or even adults
More than half of people with PH2 may eventually have mild to moderate kidney damage (chronic kidney disease stage 2 and higher)
About 35% of people with PH2 will reach kidney failure by the age of 40 years
Many people with PH2 get their first stone before they are 4 years old
Many people with PH2 will require multiple stone removal procedures throughout their lifetime
Most people with PH3 have the first signs and symptoms during infancy or childhood—half of people with PH3 have had their first stone before the age of 5 years—but the first signs of PH3 have also been reported to appear as late as 48 years of age.
Over 46% of people with PH3 develop mild kidney impairment (chronic kidney disease stage 1)
About 20% of people with PH3 will develop mild to moderate kidney disease (chronic kidney disease stages 2-3)
About 2% of people with PH3 will develop severe kidney disease (chronic kidney disease stages 4-5)
Almost everyone with PH3 has kidney stones, many before they are 3 years old
Most people have repeated kidney stones
Many children will require their first stone removal procedure before they are 5 years old
More than 70% of people will need multiple kidney stone removal procedures
For some people, kidney stone formation may decrease or stop as they reach adolescence or adulthood. Others may have frequent stones throughout adulthood.
In the United States, it’s estimated that only 10% of people with PH have PH3. However, a 2014 study suggests that it may be the most common subtype, accounting for 49% of people with PH.
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Living with your subtype
Here's what current management options look like for PH.
