Hereditary xanthinuria: report of two cases

Hereditary xanthinuria remains a poorly understood condition due to its rarity and limited clinical documentation. Prior research has established that this disorder involves altered purine metabolism, specifically the substitution of uric acid with xanthine and hypoxanthine in urine. However, few detailed case reports exist to clarify the biochemical profile and clinical manifestations. Established diagnostic methods rely on measuring purine levels in urine and plasma. This paper contributes by presenting two new cases from a single family in Taiwan. These cases add to the limited body of evidence on xanthinuria’s biochemical markers and potential familial inheritance patterns. The study also highlights the diagnostic value of high-performance liquid chromatography in identifying purine abnormalities. No prior work had resolved the full extent of purine excretion levels in affected individuals. This gap motivated the authors to document and analyze these two cases in detail.

The aim of this study was to report two cases of hereditary xanthinuria in a family from Taiwan to expand the clinical and biochemical understanding of this rare disorder. The researchers sought to confirm the presence of xanthinuria through detailed purine analysis in urine and plasma. They focused on quantifying the excretion levels of uric acid, xanthine, and hypoxanthine. The study also aimed to explore the diagnostic utility of high-performance liquid chromatography in identifying purine metabolism abnormalities. By comparing the two family members, the authors hoped to highlight similarities and differences in their biochemical profiles. This approach allows for a clearer picture of the disorder’s presentation and variability. The findings may inform future diagnostic and management strategies for xanthinuria. The study emphasizes the importance of accurate biochemical testing for rare metabolic conditions.

The authors used high-performance liquid chromatography to measure purine levels in urine and plasma samples from two patients. This analytical method enabled precise quantification of uric acid, xanthine, and hypoxanthine concentrations. The first case involved a 30-year-old woman with hypouricemia, whose urine and plasma were tested. The second case was her brother with a history of urolithiasis, who also underwent the same testing. Urine samples were analyzed for purine excretion normalized to creatinine levels. Plasma samples were similarly tested to assess circulating purine concentrations. The results were compared against standard reference ranges to identify deviations. The study did not include genetic testing or functional assays to determine the underlying cause of xanthinuria.

The first case showed extremely low uric acid excretion at 0.029 mumol/mg creatinine (30 mumol/24 hr). Xanthine excretion was significantly elevated at 1.9 mumol/mg creatinine (1935 mumol/24 hr). Hypoxanthine excretion was also high at 0.58 mumol/mg creatinine (587 mumol/24 hr). Plasma xanthine levels reached 9.3 mumol/L, while hypoxanthine was 5.8 mumol/L. Uric acid in plasma was nearly undetectable at 0.5 mumol/L. In the second case, uric acid excretion was slightly higher at 0.15 mumol/mg creatinine (189 mumol/24 hr). Xanthine excretion was 1.3 mumol/mg creatinine (1620 mumol/24 hr). Hypoxanthine excretion was 0.22 mumol/mg creatinine (276 mumol/24 hr). Plasma xanthine was 8.2 mumol/L, and hypoxanthine was 3.1 mumol/L. Uric acid in plasma was 0.8 mumol/L.

The authors concluded that both cases exhibited the hallmark biochemical features of hereditary xanthinuria, including low uric acid and elevated xanthine and hypoxanthine levels. These findings align with prior reports of the disorder. The study confirms the diagnostic utility of high-performance liquid chromatography in detecting purine metabolism abnormalities. The two cases highlight the variability in excretion levels among affected individuals. The presence of urolithiasis in one case suggests a potential clinical complication of the disorder. The authors emphasize the importance of detailed biochemical testing for accurate diagnosis. No prior work had resolved the full extent of purine excretion levels in affected individuals. The findings contribute to the limited literature on hereditary xanthinuria and may guide future clinical evaluations.