Xanthinuria

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Classification according to ICD-10
E79.8 Other disorders of the purine and pyrimidine metabolism
ICD-10 online (WHO version 2019)

The hereditary xanthinuria is an autosomal - recessive inherited metabolic disease. This is a disorder in the purine metabolism . There is a weakness in the enzyme xanthine oxidase (XO).

Epidemiology

Xanthinuria is a very rare disease. But it is recognized much less often. The time of first manifestation can vary extremely. On the one hand, the first symptoms can appear in infancy, but on the other hand only in advanced seniors . However, xanthinuria tends to affect children. Subclinical (symptom-free) forms are not uncommon. A iatrogenic (medically caused) Xanthinuria sometimes comes in gout patients by applying the XO inhibitor (xanthine oxidase inhibitor) allopurinol before. A cofactor deficiency (iron, FAD , molybdenum) of the enzyme can also reduce its activity and cause xanthinuria.

Pathogenesis

Xanthine oxidase catalyzes the conversion of hypoxanthine and xanthine into uric acid . This mainly happens in the liver and intestinal epithelia. The xanthine oxidase activity is highest there. Hydrogen peroxide (H 2 O 2 ) is produced as a by-product of this oxidation process , which has to be removed using peroxidases .

A lack of xanthine oxidase leads to a reduction in the uric acid level, as well as backlogging and thus an increase in the blood levels of xanthine and hypoxanthine. For hypoxanthine, the human metabolism ( intermediate metabolism ) has the alternative possibility of degradation via the salvage pathway (by means of the enzyme hypoxanthine phosphoribosyl transferase and return to the purine metabolism) - this is why the hypoxanthine level is less elevated. On the other hand, xanthine, which is very easily passed through the kidneys, cannot be recycled, it has to be excreted and is now excreted en masse in the urine. In the urinary tract, the o. G. Disease symptoms.

diagnosis

The high xanthine levels in the blood and urine are indicative of the diagnosis. The xanthine excretion can be increased by 15 times. The hypoxanthine level is less significantly increased due to its recycling.

Symptoms

Since xanthine has excellent renal clearance , the symptoms are almost exclusively limited to the urinary tract. Xanthine deposits in other organs, such as B. come from the muscles. Xanthinuria type II is associated with slowed intellectual development, autism , cortical kidney cysts , nephrocalcinosis , osteopenia , impaired hair formation and tooth development disorders.

One finds

and in extreme cases

therapy

There is no specific therapy. The patients have to drink a lot and have a low-purine diet . Fish (especially sardines, mackerel and anchovies) and meat (especially the offal), as well as mussels and legumes, should be avoided as much as possible. Many alcoholic beverages, especially beer, also contain purines.

Individual evidence

  1. ↑ R. Zannolli, V. Micheli u. a .: Hereditary xanthinuria type II associated with mental delay, autism, cortical renal cysts, nephrocalcinosis, osteopenia, and hair and teeth defects. In: Journal of Medical Genetics . Volume 40, number 11, November 2003, p. E121, ISSN  1468-6244 . PMID 14627688 . PMC 1735325 (free full text).

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