Sorted By Test Name - Mayo Medical Laboratories

CYSR
81067
distinguished by the pattern of urinary amino acids excretion: the former secretes large amounts of cystine
and all 3 dibasic amino acids, whereas the latter secretes more lysine and cystine than arginine and
ornithine.
Reference Values:
CYSTINE
3-15 years: 11-53 mcmol/24 hours
> or =16 years: 28-115 mcmol/24 hours
LYSINE
3-15 years: 19-140 mcmol/24 hours
> or =16 years: 32-290 mcmol/24 hours
ORNITHINE
3-15 years: 3-16 mcmol/24 hours
> or =16 years: 5-70 mcmol/24 hours
ARGININE
3-15 years: 10-25 mcmol/24 hours
> or =16 years: 13-64 mcmol/24 hours
Conversion Formulas:
Result in mcmol/24 hours x 0.24=result in mg/24 hours
Result in mg/24 hours x 4.17=result in mcmol/24 hours
See Inborn Errors of Amino Acid Metabolism in Special Instructions.
Clinical References: 1. Knoll T, Zollner A, Wendt-Nordahl G, et al: Cystinuria in childhood and
adolescence: recommendations for diagnosis, treatment, and follow-up. Pediatr Nephrol 2005
January;20(1):19-24 2. Cystinuria. In The Metabolic and Molecular Bases of Inherited Disease. 8th
edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. New York, McGraw-Hill Book Company,
2001, pp 4909-4932
Cystinuria Profile, Quantitative, Random, Urine
Clinical Information: Cystinuria is an inborn error of metabolism resulting from poor absorption and
reabsorption of the amino acid cystine in the intestine and in the kidney. This leads to an accumulation of
poorly soluble cystine in the urine and results in the production of kidney stones (urolithiasis). Symptoms
may include acute episodes of abdominal or lower back pain, presence of blood in the urine (hematuria),
and recurrent episodes of kidney stones may result in frequent urinary tract infections, which may
ultimately result in renal insufficiency. The combined incidence of cystinuria has been estimated to be 1
in 7,000. Cystinuria can be classified into 3 subtypes based on the excretion of amino acids in the urine of
heterozygotes (parents or children of affected individuals). Heterozygotes of type I excrete normal
amounts of cystine, while those with types II and III present with slight to moderate excretion of cystine
and other dibasic amino acids (lysine, arginine, and ornithine). All 3 subtypes are caused by mutations in
only 2 genes, SLC3A1 on chromosome 2p and SLC7A9 on chromosome 19q. A new classification
system has been proposed to distinguish the various forms of cystinuria: type A, due to mutations in the
SLC3A1 gene; type B, due to mutations in the SLC7A9 gene; and type AB, due to 1 mutation in each
SLC3A1 and SLC7A9.
Useful For: Biochemical diagnosis and monitoring of cystinuria
Interpretation: Homozygotes or compound heterozygotes with cystinuria excrete large amounts of
cystine in urine, but the amount varies markedly. Urinary excretion of other dibasic amino acids (arginine,
lysine, and ornithine) is also typically elevated. Plasma concentrations are generally normal or slightly
decreased. Individuals who are homozygous and heterozygous for non-type I cystinuria can be
distinguished by the pattern of urinary amino acids excretion: homozygous individuals secrete large
amounts of cystine and all 3 dibasic amino acids, whereas heterozygous individuals secrete more lysine
and cystine than arginine and ornithine.
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