The Lesch-Nyhan syndrome--an under-recognised condition in South Africa? A case report.

The Lesch-Nyhan syndrome is a rare inborn error of purine metabolism caused by a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), which results in mental retardation with characteristic self-mutilation, spasticity, extrapyramidal signs and hyperuricaemia. The clinical and biochemical findings in an 18-month-old boy, who presented with renal calculi and was shown to have less than 1% of normal HGPRT activity, are reported. The obvious neurological abnormalities had previously been thought to be due to hypoxic-ischaemic encephalopathy. The expected incidence of this disease is much higher than the known number of cases diagnosed.