Medicine

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USMLE Step 1

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Metabolic Disorders

Cystinuria

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Cystinuria is an autosomal recessive disorder caused by impaired renal reabsorption of several amino acids.

The renal reabsorption of the amino acids cysteine, ornithine, lysine, and arginine ("COLA" amino acids) are impaired, leading to increased excretion of these amino acids in the urine.

High urinary levels of cysteine can induce the formation of cystine kidney stones, which are hexagonal under the microscope. The cyanide-nitroprusside test can be used to determine cystine concentrations in the urine.

Treatment focuses on preventing the formation of kidney stones, and includes alkalinizing agents like potassium citrate and acetazolamide, as well as chelators like penicillamine. Like all kidney stone pathologies, symptoms are also improved by ample hydration.

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