Primary hyperoxaluria is a rare condition (autosomal recessive), resulting in increased excretion of oxalate (up to 600 mg a day from normal 50 mg a day), with oxalate stones being common. Signs and symptoms
Primary hyperoxaluria is an autosomal recessive disease, meaning both copies of the gene contain the mutation. Both parents must have one copy of this mutated gene to pass it on to their child, but they do not typically show signs or symptoms of the disease. A single kidney stone in children or recurrent stones in adults is often the first warning sign of primary hyperoxaluria. Other symptoms range from recurrent urinary tract infections, severe abdominal pain or pain in the side, blood in the urine, to chronic kidney disease and kidney failure. The age of symptom onset, progression and severity can vary greatly from one person to another, even among members of the same family. Some individuals may have mild cases that go undiagnosed well into adulthood; others may develop severe complications during infancy, which may result in early death. Pathophysiology
The buildup of oxalate in the body causes increased renal excretion of oxalate (hyperoxaluria), which in turn results in kidney and bladder stones. Stones cause urinary obstruction (often with severe and acute pain), secondary infection of urine and eventually kidney damage. Primary hyperoxaluria is caused by genetic defects that result in the overproduction of oxalate.
This is different from secondary hyperoxaluria, which is caused by the increase in dietary and intestinal absorption of oxalate or excessive intake of oxalate precursors.Oxalate stones in primary hyperoxaluria tend to be severe, resulting in relatively early kidney damage (in teenage years to early adulthood), which impairs the excretion of oxalate leading to a further acceleration in  accumulation of oxalate in the body.After the development of kidney failure patients may get deposits of oxalate in the bones, joints and bone marrow. Severe cases may develop haematological problems such as anaemia and thrombocytopaenia. The deposition of oxalate in the body is sometimes called "oxalosis" to be distinguished from "oxaluria" which refers to oxalate in the urine. Diagnosis
A diagnosis of primary hyperoxaluria is suspected based on presenting patient characteristics such as kidney stones in infants or children, recurrent kidney stones in adults, or family history of hyperoxaluria. In these patients, stone analysis and urine analysis are recommended to rule out secondary causes of hyperoxaluria. A definitive diagnosis of primary hyperoxaluria requires genetic testing. This is performed using a gene panel covering known mutations for all three types of primary hyperoxaluria. Classification
The three main types of primary hyperoxaluria (PH1, PH2, and PH3) are each associated with mutations in specific genes involved in the metabolism of glyoxylate, the precursor of oxalate. These mutations result in decreased production or activity of the proteins that are involved in the normal breakdown of glyoxylate, which results in an overproduction of oxalate.