Xanthinuria Type 1 with a Novel Mutation in Xanthine Dehydrogenase and a Normal Endothelial Function

Area of Science:

• Biochemistry
• Genetics
• Nephrology

Background:

• Xanthinuria is a rare metabolic disorder characterized by the absence of uric acid in serum and urine.
• The association between extremely low serum uric acid (SUA) levels in xanthinuria and endothelial dysfunction or exercise-induced acute kidney injury (EIAKI) remains largely unexplored.

Observation:

• A 59-year-old woman presented with undetectable SUA and urine UA, alongside elevated urinary hypoxanthine and xanthine.
• Genetic analysis identified novel homozygous mutations in the xanthine dehydrogenase (XDH) gene (c.1585 C>T, p. Gln529*).
• The patient had no history of EIAKI or urolithiasis.

Findings:

• Flow-mediated dilation, a marker of endothelial function, was within the normal range.
• This case demonstrates preserved endothelial function in an individual with xanthinuria due to novel XDH mutations and extremely low SUA.

Implications:

• This case report suggests that extremely low SUA levels and xanthinuria may not necessarily lead to endothelial dysfunction.
• Further research is warranted to understand the long-term cardiovascular and renal implications of xanthinuria and associated genetic mutations.