Hyperoxaluria occurs when there is too much of a substance called oxalate in the urine. There are several types of hyperoxaluria:
Primary hyperoxaluria. Primary hyperoxaluria is a rare inherited (genetic) condition present at birth. In this type, the liver doesn't create enough of a certain protein (enzyme) that prevents overproduction of oxalate, or the enzyme doesn't work properly. Excess oxalate is eliminated through your kidneys, in your urine. The extra oxalate can combine with calcium to create kidney stones and crystals, which can damage the kidneys and cause them to stop working (renal failure).
Kidney stones form early and most often cause symptoms during childhood or adolescence. Because of the very large amounts of oxalate produced, most people's kidneys fail by early to middle adulthood, but renal failure can occur as early as infancy. To date, experts have identified three different genetic causes of primary hyperoxaluria.