Xanthinuria

Hereditary Xanthinuria is an autosomal recessive inherited metabolic disease. This is a disorder in purine metabolism. There is a weakness of the enzyme xanthine oxidase ( XO).

Epidemiology

The Xanthinuria is a very rare disease. But it is recognized even rarer. The timing of onset can vary extremely. It may occur the first symptoms at an advanced senility to an already in infancy, on the other hand. The trend concerns the Xanthinuria but children. Subclinical ( asymptomatic ) course forms are not rare. An iatrogenic ( medically caused ) Xanthinuria sometimes comes in gout patients by application of the XO inhibitor ( xanthine oxidase inhibitor ), allopurinol. Also a cofactor limitations (iron, FAD, molybdenum ) of the enzyme can throttle its activity, and a Xanthinuria condition.

Pathogenesis

Xanthine oxidase catalyzes the conversion of hypoxanthine to xanthine and uric acid. This is done mainly in the liver and the intestinal epithelia. There the Xanthinoxidaseaktivität is highest. As a byproduct of this oxidizing process produces hydrogen peroxide (H2O2), which must be removed by means of peroxidases.

A deficiency of xanthine oxidase leads to a lowering of uric acid levels, as well as to the accumulation and thus an increase in blood levels of xanthine and hypoxanthine. Since the human metabolism ( intermediary metabolism ), the possibility has, rather than to recycle the degradation, hypoxanthine via the salvage pathway (via the enzyme hypoxanthine phosphoribosyltransferase ) and inject again in purine metabolism, the hypoxanthine levels are less strongly increased. However, xanthine can not be recycled. It is for this molecule only the ability to excrete it. This now existing in excess xanthine, is very good through the kidneys. It is excreted en masse in the urine and causes in the lower urinary tract symptoms.

Diagnosis

Leading the way for the diagnosis is the high xanthine levels in blood and urine. The xanthine excretion may be increased by a factor of 15. The hypoxanthine level is increased less significantly due to its recycling.

Symptoms

Since xanthine has excellent Nierengängigkeit ( renal clearance ), the symptoms limited almost exclusively to the urinary tract. Very rarely it can also xanthine deposits in other organs, such as are, for example the muscles. The Xanthinuria type II is associated with delayed mental development, autism, cortical renal cysts, nephrocalcinosis of osteopenia, impaired hair formation and tooth development disorders.

One can find

• Nephrolithiasis or urolithiasis: xanthine stones in the kidneys and urinary tract,
• Crystalluria: resignation of Harnkristallen

And in extreme cases

• Acute renal failure: This can be fatal under certain circumstances.

Therapy

No specific therapy does not exist. The patient must drink a lot and eat purine. Should be avoided if possible fish (especially sardines, mackerel and anchovies ) and meat (especially organ meats ), as well as shellfish and legumes. Many alcoholic beverages, especially beer, contain purines.