Lesch-Nyhan disease may show a spectrum of phenotypic features determined by the level of residual enzyme activity.
Gene affected: HPRT1 (hypoxanthine-guanine phosphoribosyltransferase)
Function of enzyme: purine recycling
Over 400 mutations have been described. Classic Lesch-Nyhan phenotype is associated with null mutation associated with no enzyme activity. Other mutations may be associated with some residual enzyme activity.
Almost all patients will have overproduction of uric acid with risk for gout and nephrolithiasis.
Phenotypic features to evaluate:
(1) self-injurious behavior
(3) muscle control
(4) other neurological findings
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