Lesch–Nyhan syndrome

Lesch–Nyhan syndrome is an X-linked recessive disorder caused by severe deficiency of hypoxanthine-guanine phosphoribosyltransferase. It causes excess uric acid production and neurological and behavioral symptoms, often including self-injury.

Hypoxanthine-guanine phosphoribosyltransferase: An enzyme that salvages hypoxanthine and guanine by converting them into nucleotide forms. Its near-total deficiency is the defining biochemical defect in Lesch–Nyhan syndrome.
Hyperuricemia: An abnormally high concentration of uric acid in the blood. It is a common biochemical consequence of purine overproduction in the syndrome.
Michael Lesch: An American pediatrician who co-described the syndrome in 1964. His clinical report with William Nyhan first delineated the disorder.
HPRT1-related neurologic dysfunction: A disorder caused by partial HPRT1 deficiency, with neurological symptoms but generally less severe than Lesch–Nyhan syndrome. Residual enzyme activity distinguishes this broader, milder phenotype from classic syndrome.
Purine salvage pathway: A set of reactions that recycles purine bases into nucleotides. The defective enzyme normally returns hypoxanthine and guanine to this pathway.
Nephrolithiasis: The formation of calculi in the kidneys or urinary tract. Excess uric acid can form urinary stones, especially before diagnosis or treatment.
William Nyhan: An American pediatrician and geneticist known for describing inherited metabolic disorders. He co-authored the 1964 report that identified the syndrome’s clinical pattern.
Kelley–Seegmiller syndrome: A disorder caused by partial hypoxanthine-guanine phosphoribosyltransferase deficiency, usually dominated by uric acid complications. It shares HPRT1-related hyperuricemia but typically lacks classic self-injurious behavior.
Uric acid: The final product of purine breakdown in humans, normally excreted in urine. Its overproduction causes hyperuricemia and can produce kidney and joint complications.
Molecular genetic testing: Laboratory analysis of DNA to identify disease-associated genetic variants. Variants in HPRT1 can confirm the diagnosis and support family testing.

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