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Cystinuria and Cystine Calculi

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Abstract

CYSTINURIA, or the presence of abnormally large and consistent amounts of cystine in the urine, is a result of permanent physiologic upset of protein and sulfur metabolism Cystine is a sulfur-containing amino acid present in protein foods which, in normal metabolism is oxidized principally to sulfate with a smaller amount converted to taurine. In the patient with, cystinuria, however, there is failure of intermediary enzyme oxidation of cystine into sulfate and cystine is excreted in the urine in amounts which may be as high as 1 Gm. per liter of urine in a 24 hour period. Normal urine contains only a few mg. (0.8–80 mg. daily) cystine per liter.

This incurable metabolic defect has been recognized for nearly 100 years, but has escaped widespread attention of the medical profession because of the rarity of cystine lithiasis and hence of clinical manifestations. Many patients pass through life without knowledge of their metabolic abnormality. It has been estimated by Eppinger1 that approximately 2.7 per cent of those with cystinuria develop calculi and subsequent clinical symptoms. An indication of the relative incidence of cystinuria can be gleaned from the findings of Lewis2 who reported 29 positive cystine urine tests in 11,000 healthy young men and women.

Cystine lithiasis is a rapidly progressive variety of urinary calculosis with a high tendency to recurrence. A few patients, unaccountably, are prone to form calculi in the urinary tract while the majority escape this complication. Experimental clinical and pathologic studies suggest that some lesion of the tubular. . .


 

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