What is Primary Hyperoxaluria Type 3?
Primary hyperoxaluria (PH) is an inherited disease in which a lack of a particular liver enzyme causes the body to accumulate a substance called oxalate. Excess oxalate leads to a buildup of insoluble calcium salts in the kidneys, which may cause kidney stones and progressive kidney damage. PH type 3 (PH3) is caused by harmful genetic changes (mutations) in the HOGA1 gene. Approximately 10% of PH cases are of the PH3 subtype. Symptoms of PH3 are similar to those of PH1 and PH2 but are generally milder, with lower urinary oxalate excretion and the earliest onset of the three subtypes. Unlike PH1 and PH2, which can affect other organs, buildup of oxalate in PH3 is only in the kidneys.
People with PH3 are at increased risk of developing kidney stones. Symptoms can develop any time from infancy to adulthood. Approximately 50% of affected individuals develop kidney stones by five years of age, but many experience a decrease in the incidence of kidney stones by adulthood. Some individuals do not develop symptoms until adulthood. Frequent kidney stones can affect kidney function; however, individuals with PH3 rarely progress to kidney failure.
How common is Primary Hyperoxaluria Type 3?
The incidence of PH3 in the population is 1 in 165,000 births. The incidence of PH3 is more common among individuals of Ashkenazi Jewish descent.
How is Primary Hyperoxaluria Type 3 treated?
Treatments for PH3 mainly aim to prevent the formation and deposition of calcium oxalate. Individuals with the condition should drink plenty of water. Intravenous (IV) fluids may be necessary during periods of illness or times of limited fluid intake. A physician may prescribe medication or vitamins to help lower oxalate levels and inhibit the formation of kidney stones. Dietary restriction of foods high in oxalate may be beneficial. Unlike with other types of PH, individuals with PH3 rarely require dialysis or kidney or liver transplantation.
What is the prognosis for an individual with Primary Hyperoxaluria Type 3?
Individuals with PH3 often have formation of multiple kidney stones. In many individuals with PH3, kidney stone formation decreases as they reach adulthood. Transplants are not necessary in most individuals with PH3, and there are few reports of progression to kidney failure.