Xanthine
Overview
Xanthine is a purine base and intermediate metabolite in the degradation pathway of purines, formed from hypoxanthine by xanthine oxidase and further converted to uric acid. It serves as a marker of purine catabolism and xanthine oxidase activity, which generates reactive oxygen species during its catalytic function. Elevated xanthine levels may indicate increased cell turnover, such as in malignancy, tissue ischemia, or inborn errors of purine metabolism like xanthinuria; low levels are less clinically significant. Clinically, xanthine measurement aids in diagnosing xanthinuria, assessing molybdenum cofactor deficiency, and evaluating tumor lysis syndrome risk or purine metabolism disorders.
Clinical Use Cases
- Diagnosis of hereditary xanthinuria (types I and II) with low uric acid and xanthine stones.
- Evaluation of molybdenum cofactor deficiency or xanthine oxidase deficiency.
- Monitoring purine metabolism in Lesch-Nyhan syndrome or other purine disorders.
- Assessment of tumor lysis syndrome or high cell turnover states in oncology.
- Research into oxidative stress and ischemia-reperfusion injury.
Specimen Types
- Plasma or serum.
- Urine (24-hour or spot).
- Cerebrospinal fluid in metabolic disorders.
- Amniotic fluid for prenatal diagnosis.
Measurement Methods
- High-performance liquid chromatography (HPLC) with UV detection.
- Liquid chromatography-mass spectrometry (LC-MS/MS).
- Enzymatic assays coupled with spectrophotometry.
- Capillary electrophoresis.
Test Preparation and Influencing Factors
- No fasting required.
- Allopurinol or febuxostat (xanthine oxidase inhibitors) decrease xanthine levels.
- High purine diet (e.g., organ meats, seafood) may transiently elevate levels.
- Renal function affects urinary excretion; dehydration concentrates urine xanthine.
- Hemolysis or sample contamination can interfere with assays.
- Timing: collect during symptomatic periods or after purine load if indicated.
Synonyms
- 3,7-Dihydropurine.
- 2,6-Dioxopurine.