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USMLE Step 1

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Metabolic Disorders

Lesch-Nyhan Syndrome

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Lesch-Nyhan Syndrome is a X-linked recessive metabolic disorder resulting in the accumulation of uric acid.

Specifically, the disease is caused by defects in HGPRT (hypoxanthine guanine phosphoribosyltransferase), an enzyme necessary for salvaging/recycling purine bases into purine nucleotides (see Purine Salvage).

This defect in purine salvage causes free purine bases to be excreted rather than recycled, with an increase in uric acid, an intermediate for purine excretion (see Purine Excretion).

Clinical findings include self mutilation and compulsive aggressive behavior, dystonia, as well as intellectual disability ordevelopmental delay. Elevated uric acid can precipitate in the joints, causing gout and podagra, as well as in the urine, as "orange sand"-like crystals in diapers of affected patients.

Find this Lesch-Nyhan Syndrome mnemonic and more mnemonics for Metabolic Disorders among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.