The hypoxanthine-guanine phosphoribosy transferase (HPRT) deficiency is an X-linked recessive disorder in­volving the purine salvage system. The alterations in the HPRT gene that lead to the disease are varied and are represented by point mutations, insertions, deletions and errors in RNA splicing. Symptoms of the disease are usu­ally divided into two syndromes, depending on the resid­ual activity of the enzyme. Partial deficiency of HPRT, corres­ponding to the Kelley-Seegmiller syndrome (KSS), consists of hyperuricemia, gouty arthritis, uricolithiasis with follow­ing nephropathy. Complete deficiency, the Lesch-Nyhan syndrome (LNS), which, besides the above symptoms, includes self-mutilation and profound neuro­logical dysfunction, that confines the victims to a wheel­chair at an early age. A third group of partially HPRT deficient patients have mild to severe neurological symp­toms without self-mutilation. We have used the newest and most exact classification, that groups patients into four types, in an attempt to correlate more precisely the clinical variants of the HPRT deficiency with their gene alter­ations.

Key words: Gene alterations, hypoxanthine-guanine phosphoribosy transerase (HPRT), Kelley-Seegmiller syndrome (KSS), Lesch-Nyhan syndrome (LNS), pheno-type-genotype correlation of HPRT deficiency