描述
Lesch-Nyhan Syndrome (LNS; Hypoxanthin guanine phosphoribosyltransferase deficiency) is caused by a complete defect in the HPRT1 gene which codes for hypoxanthine-guanine phosphoribosyltransferase. Hypoxanthine-guanine phosphoribosyltransferase is an enzyme in purine metabolism. Its primarily functions to salvage purines from degraded DNA to renewed purine synthesis. In this role, it acts as a catalyst in the reaction between guanine and phosphoribosyl pyrophosphate (PRPP) to form GMP. A complete deficiency in this enzyme causes overproduction of uric acid, therefore it results in accumulation of uric acid in serum and increase urinary excretion of uric acid. Symptoms and signs include severe gout and kidney problems, poor muscle control, and moderate mental retardation. These complications usually appear in the first year of life. A striking feature of LNS is self-mutilating behaviors, characterized by lip and finger biting, that begin in the second year of life. Neurological symptoms include facial grimacing, involuntary writhing, and repetitive movements of the arms and legs similar to those seen in Huntington’s disease. Treatment for LNS is symptomatic. Gout can be treated with allopurinol to control excessive amounts of uric acid. Kidney stones may be treated with lithotripsy, a technique for breaking up kidney stones using shock waves or laser beams. There is no standard treatment for the neurological symptoms of LNS. Some may be relieved with the drugs carbidopa/levodopa, diazepam, phenobarbital, or haloperidol.