Unusual Presentation of Kelley-Seegmiller Syndrome

Abstract

Female carriers of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency have somatic cell mosaicism of HPRT activity and are healthy. We report a 50-year-old woman without gout or nephrolithiasis. She was never on allopurinol. Normal serum uric acid concentrations, increased plasma hypoxanthine, and xanthine were found. HPRT activity in erythrocytes was surprisingly low: at 8.6 nmol h⁻¹ mg ⁻¹ haemoglobin. Mutation analysis revealed a heterozygous HPRT gene mutation, c.215A > G (p.Tyr72Cys). Assessment of X-inactivation ratio has shown that > 75% of the active X-chromosome bears the mutant allele and could explain these unusual, previously undescribed findings.

Keywords:

• Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency
• Lesch-Nyhan disease variants
• hyperuricemia
• gout

Notes

∗–on allopurinol therapy, Hb–haemoglobin.