Xanthine dehydrogenase deficiency with novel sequence variations presenting as rheumatoid arthritis in a 78-year-old patient.

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This report describes the clinical , biochemical and molecular data of a 78 -year -old patient with xanthine dehydrogenase deficiency presenting as rheumatoid arthritis .Xanthinuria type I is a rare disorder of purine metabolism caused by xanthine dehydrogenase (XDH ) deficiency ; fewer than 150 cases have been described in the literature so far .We describe the clinical history and urine and serum findings of a 78 -year -old patient with isolated XDH deficiency presenting as rheumatoid arthritis . The diagnosis was confirmed by mutation analysis .The patient suffered from arthral symptoms and nephrocalcinosis . Very low concentrations of uric acid were observed in her serum and urine . The allopurinol loading test indicated her xanthinuria to be type I . Analysis of genomic DNA revealed novel heterozygous deletion in exon 8 (g .27073 delC , p .214 QfsX 4 ) and previously published heterozygous nucleotide missense transition in exon 25 (g .64772 -C >T , p .T 910 M ).Hereditary xanthinuria is a rare disorder , but it also needs to be considered in patients not originating from Mediterranean countries or the Near or Middle East . Urate concentration in serum and urine may provide an initial indication of XDH deficiency before high -performance liquid chromatography (HPLC ) analysis is performed . The key to identifying the disorder is a greater awareness of XDH deficiency amongst primary care physicians , nephrologists , and urologists , but also rheumatologists . The diagnosis and therapeutic management requires a multidisciplinary approach .