Primary hyperoxaluria

Primary hyperoxaluria results in increased excretion of oxalate, with oxalate stones being common. The oxalalate in these common condtions is derived from dietary sources or is secondary to malasorption. Primary hyperoxaluria, on the other hand, refers to a specific type of hyperoxaluria that is due to a metabolic defect resulting from a heritable genetic defect.

The buildup of oxalate in the body causes increased excretion of oxalate, which in turn results in renal and bladder stones. Stones cause urinary obstruction (often with severe and acute pain), secondary infection of urine and eventually kidney damage.

Oxalate stones in primary hyperoxaluria tend to be severe, resulting in relatively early kidney damage (say teenage, early adulthood), which impairs the excretion of oxalate leading to a further acceleration in accumulation of oxalate in the body.

After the development of renal 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.

Renal failure is a serious complication requiring treatment in its own right. Dialysis can control renal failure but tends to be indadequate to dispose of excess oxalate. Renal transplant is more effective and this is the primary treatment of severe hyperoxaluria. Liver transplantation (often in addition to renal transplant) may be able to control the disease by correcting the metabolic defect.

There are two main types of primary hyperoxaluria, each associated with specific metabolic defects.