American Board Of Psychiatry And Neurology (ABPN) Practice Exam

Lesch-Nyhan syndrome is specifically caused by a deficiency in hypoxanthine-guanine phosphoribosyltransferase (HGPRT). This enzyme plays a crucial role in the purine salvage pathway, which recycles purines to help maintain the nucleotide pool within cells. When this enzyme is deficient or absent, it leads to an accumulation of uric acid due to the overproduction of purines, resulting in the characteristic features of Lesch-Nyhan syndrome, such as severe neurological deficits, behavioral abnormalities, and self-mutilating behaviors, along with hyperuricemia. The other enzymes listed are associated with different metabolic disorders. For instance, ornithine transcarbamylase is involved in the urea cycle, and its deficiency leads to hyperammonemia rather than symptoms related to Lesch-Nyhan syndrome. Adenylosuccinate deficiency impacts purine metabolism as well, but it causes a different set of symptoms. Lastly, arginase deficiency is tied to urea cycle disorders, resulting in issues related to ammonium accumulation rather than the specific clinical manifestations seen in Lesch-Nyhan syndrome.