<prompt> Lesch - Nyhan Syndrome - associated withPurine necleoside phosphorylase deficiencyAdenosine deaminase deficiencyHypoxanthine - guanine phosphoribosyl transferase defectXanthine oxidase deficiency  <response>: It is X-linked inherited disorder of purine metabolismDeficiency of HGPase, so the rate of salvage pathway is decreased resulting in the accumulation of PRPP and decreased level of inhibitory purine nucleotide Disease is characterized by self-mutilation, mental retardation excessive uric acid and nephrolithiasis Ref: DM Vasudevan, 7th edition, page no: 568 