A child presented at 2 years of age with delayed motor development, mental retardation and finger biting. He was normal at bih. He subsequently develops cerebral palsy ahritis and dies due to renal failure at age of 25 years. What is the likely enzyme deficiency implicated?

Ans: C. HGP deficiency(Ref: Nelson 20/e p746-747)Lesch-Nyhan syndrome:Complete HGP deficiency characterized by hyperuricemia, self-mutilative behavior, choreoathetosis, spasticity & mental retardation.HP gene:Located on X chromosome.Affected males - Hemizygous for mutant gene.Carrier females - Asymptomatic.Paial HP deficiency:Kelley!Seegmiller syndrome associated with hyperuricemia without CNS manifestations.Hyperuricemia - Due to urate overproduction a Causing uric acid crystalluria, nephrolithiasis, obstructive uropathy & gouty ahritis.Early diagnosis and appropriate therapy with allopurinol can prevent or eliminate all the problems attributable to hyperuricemia without affecting behavioral or neurologic abnormalities.