Lesch-Nyhan Syndrome

Lesch- Nyhan syndrome (LNS) is a rare X-linked disorder of purine metabolism associated with hyperuricemia and caused by absence or near complete absence of the enzyme hypoxanthine- guanine phosphoriboxyl transferase (HGPRT), essential for purine salvage (Nyhan 2004, Seegmiller et al. 1967, Torres and Puig 2007). The gene for HGPRT has been mapped to position Xq2.6 (OMIM # 308000). The disease phenotype includes hyperuricemia, dystonia, choreoathetosis, hypertonia, hyperreflexia, varying degrees of cognitive impairment, and the hallmark symptom of severe self-mutilation. Besides the classical LNS (caused by virtually 0% HGPRT activity under any conditions) several enzymatic variants (with HGPRT activities varying from 0 to 50% or near normal) have been recognised including (a) neurological variants; and (b) partial variants (Nyhan 2004).