Primary Hyperoxaluria

What is primary hyperoxaluria?

Primary hyperoxaluria is a rare condition characterised by the overproduction of a substance called oxalate (or oxalic acid). In the kidneys, the excess oxalate combines with calcium to form calcium oxalate, a hard compound that is the main component of kidney stones. Deposits of calcium oxalate can lead to kidney damage, kidney failure, and injury to other organs.

Primary hyperoxaluria is caused by the shortage (deficiency) of an enzyme that normally prevents the buildup of oxalate. There are two types of primary hyperoxaluria, distinguished by the enzyme that is deficient. People with type 1 primary hyperoxaluria have a shortage of a liver enzyme called alanine-glyoxylate aminotransferase (AGXT). Type 2 primary hyperoxaluria is characterised by a shortage of an enzyme called glyoxylate reductase/hydroxypyruvate reductase (GRHPR).

How common is primary hyperoxaluria?

Type 1 primary hyperoxaluria is estimated to occur in 1 per 60,000 to 120,000 live births; it is more common in some Mediterranean countries, such as Tunisia. The incidence of type 2 primary hyperoxaluria is unknown; it is less common than type 1.

What genes are related to primary hyperoxaluria?

Mutations in the AGXT and GRHPR genes cause primary hyperoxaluria.

The breakdown (metabolism) and processing of certain sugars and amino acids (the building blocks of proteins) produces a substance called glyoxylate. Normally, glyoxylate is converted to the amino acid glycine or to a compound called glycolate through the action of two enzymes, alanine-glyoxylate aminotransferase and glyoxylate reductase/hydroxypyruvate reductase, respectively. Mutations in the AGXT or GRHPR gene cause a shortage of these enzymes, which prevents the conversion of glyoxylate to glycine or glycolate. As levels of glyoxylate build up, it is converted to oxalate. Oxalate combines with calcium to form calcium oxalate deposits, which can damage the kidneys and other organs.

How do people inherit primary hyperoxaluria?

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

What other names do people use for primary hyperoxaluria?

• D-glycerate dehydrogenase deficiency
• glyceric aciduria
• glycolic aciduria
• hepatic AGT deficiency
• HP1
• HP2
• Hyperoxaluria, Primary
• Oxalosis
• Oxaluria, Primary
• peroxisomal alanine:glyoxylate aminotransferase deficiency