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Cystinosis, Cystine, Cystine Kidney Stones Print E-mail

Dr. Kennedy

Cystinosis is a genetic disease characterized by the widespread deposition of cystine (pronounced sis-stein) in cells due to a defect in cystine transport. Cystine normally forms after protein degradation and is transported from structures called lysosomes into the cytoplasm. In cystinosis, cystine accumulates in the lysosomes and eventually forms crystals throughout the body. Cystinosis is therefore a lysosomal storage disease.) The disease is inherited in an autosomal recessive manner Cystine is an amino acid notable because it is the least soluble of all of the naturally occurring amino acids and because it precipitates out of solution in the genetic disease cystinuria (a special instance of cystinosis) to form stones in the urinary tract. Cystine is the chief sulfur-containing compound in protein. Cystine is generated by the union of two cysteine (pronounced sis-teen) molecules and so is sometimes called dicysteine. It is abbreviated Cys-Cys

Cystine kidney stones are thus due to cystinuria, which is an inherited disorder of the transport of an amino acid (a building block of protein) called cystine that results in an excess of cystine in the urine (cystinuria) and the formation of cystine stones. Cystinuria is the most common defect in the transport of an amino acid. Although cystine is not the only overly excreted amino acid in cystinuria, it is the least soluble of all naturally occurring amino acids. Cystine tends to precipitate out of urine and form stones in the urinary tract. Small stones are passed in the urine, however big stones remain in the kidney (nephrolithiasis) impairing the outflow of urine while medium-size stones make their way from the kidney into the ureter and lodge there further blocking the flow of urine. Obstruction of the urinary tract puts pressure back up the ureter and kidney causing the ureter to widen and the kidney to be compressed. Obstruction also causes the urine to be stagnant, an open invitation to repeated urinary tract infection. The pressure on the kidneys and the urinary infections results in damage to the kidneys. The damage can progress to renal insufficiency and end-stage kidney disease, requiring renal dialysis or a transplant.

The stones are responsible for all the signs and symptoms of cystinuria, including

  • hematuria -- blood in the urine
  • flank pain
  • renal colic - intense, cramping pain due to stones in the urinary tract
  • obstructive uropathy -- urinary tract disease due to obstruction; and urinary tract infections.

The information in this article is not meant to be medical advice.�Treatment for a medical condition should come at the recommendation of your personal physician.

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