A NEW POINT MUTATION IN A HYPOXANTHINE PHOSPHORIBOSYLTRANSFERASE-DEFICIENT PATIENT

A 12-year-old boy was referred because of abdominal pain, gross hematu ria, and passage of stones. Further evaluation showed growth delay, lo w average range of intellectual functioning, and a speech articulation dis order. No signs of self-mutilation or self-injurious behavior wer e present. He had hyperuricemia, hyperuricosuria, uric acid crystallur ia, uric acid calculi, macrocytosis, megaloblastic bone marrow changes , and mild anemia. Hypoxanthine phosphoribosyltransferase (HPRT) enzym e activity was reduced to approximately 26% of normal. Polymerase chai n reaction-single strand conformational polymorphism analysis of the H PRT gene in DNA isolated from the patient's blood lymphocytes revealed a single nucleotide substitution at codon 200 in exon 8. The base cha nge was a guanine to cytosine transversion, resulting in the conservat ive amino acid substitution of threonine in place of arginine. To our knowledge, this mutation has not previously been reported.