Primary hyperoxaluria (PH) occurs due to an autosomal recessive hereditary disorder of the metabolism of
glyoxylate, which causes excessive
oxalate production. The most frequent and serious disorder is due to
enzyme deficit of
alanine-glyoxylate aminotransferase (PH type I) specific to hepatic peroxisome. As
oxalate is not metabolised in humans and is excreted through the kidneys, the kidney is the first organ affected, causing recurrent
lithiasis,
nephrocalcinosis and early
renal failure. With advance of
renal failure, particularly in patients on haemodialysis (HD),
calcium oxalate is massively deposited in tissues, which is known as
oxalosis. Diagnosis is based on family history, the presence of
urolithiasis and/or
nephrocalcinosis,
hyperoxaluria,
oxalate deposits in tissue forming
granulomas, molecular analysis of
DNA and
enzyme analysis if applicable. High diagnostic suspicion is required; therefore, unfortunately, in many cases it is diagnosed after its recurrence following
kidney transplantation.
Conservative management of this disease (high liquid intake,
pyridoxine and crystallisation inhibitors) needs to be adopted early in order to delay kidney damage. Treatment by dialysis is ineffective in treating excess
oxalate. After the kidney transplant, we normally observe a rapid appearance of
oxalate deposits in the graft and the results of this technique are discouraging, with very few exceptions. Pre-emptive
liver transplantation, or simultaneous liver and kidney transplants when there is already irreversible damage to the kidney, is the treatment of choice to treat the underlying disease and suppress
oxalate overproduction. Given its condition as a
rare disease and its genetic and clinical heterogeneity, it is not possible to gain evidence through randomised clinical trials. As a result, the recommendations are established by groups of experts based on publications of renowned scientific rigour. In this regard, a group of European experts (OxalEurope) has drawn up recommendations for diagnosis and treatment, which were published in 2012.