Xanthine Stones in an Infant: A Case Report and Clinical Insights

Xanthinuria is a rare autosomal recessive condition characterised by increased urinary xanthine excretion resulting from a derangement in purine metabolism, accounting for only 0.1% of pediatric stones.Incidence of inherited xanthinuria lies in the range of 1:6,000 to 1:69,000.A male baby in the latter part of infancy presented with a history of recurrent episodes of abdominal pain, fever, vomiting for 4 months, and a recent history of passage of calculi.On evaluation, radiolucent calculi were noted in the left renal pelvis and in the bilateral distal ureters, causing hydroureteronephrosis.During initial cystoscopy, a posterior urethral valve was incidentally noted and fulgurated.Ureteroscopic lithotripsy in two sessions cleared the stone burden.Crystallographic analysis of the stone was suggestive of a xanthine stone.Selective genetic analysis for XDH1 gene targeting exons 6F, 8F, 10F, 16F, 21F, 23F, was done on samples from the index case, first and second degree relatives.Interestingly, no mutations were recorded in the index case, but a mutation was noted in one first-degree relative and one second-degree relative, respectively, in exons 21F [c.2211C>T (p.I737I)] and 8F [g.682G>C (p.T202T)].As only targeted gene analysis was done, the possibility of mutations in other exons of the XDH1 gene cannot be ruled out.A complete metabolic workup along with stone analysis helps in the early diagnosis of metabolic conditions like xanthinuria, which can be further confirmed with genetic studies.Diet and lifestyle changes can help in preventing recurrence of stones and avoiding further renal damage.