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Cystinuria
Classification and external resources

Chemical structure of cystine formed from L-cysteine (under biological conditions)
ICD-10 E72.0
ICD-9 270.0
OMIM 220100
DiseasesDB 3339
MedlinePlus 000346
eMedicine med/498
MeSH D003555

Cystinuria is an inherited autosomal recessive[1] metabolic disorder that is characterized by the formation of cystine stones in the kidneys, ureter, and bladder.

Contents

Signs and symptoms

Cystinuria is a cause of persistent kidney stones. It is a disorder of the amino acid transporter for positively charged amino acids, namely Cysteine. Cystinuria is difficult to diagnose, and is one of many causes of kidney stones. If not treated properly, the patient could experience serious injury to the kidneys and to surrounding organs, and in some rare cases death. The stones form yellow-brown hexagonal crystals and are identified by a positive nitroprusside cyanide test.

Causes

Cystinuria is characterized by the inadequate reabsorption of cystine in the proximal convoluted tubules during the filtering process in the kidneys, thus resulting in an excessive concentration of this amino acid in the urine. Cystine may precipitate out of the urine, if the urine is neutral or acidic, and form crystals or stones in the kidneys, ureters, or bladder. It is one of several inborn errors of metabolism included in the garrod's tetrad. The disorder is attributed to deficiency in transport and metabolism of amino acids.

Pathophysiology

Cystinuria has an autosomal recessive pattern of inheritance.

Mutations in the SLC3A1 and SLC7A9 genes cause cystinuria. The SLC3A1 and SLC7A9 genes provide instructions for producing the two parts of a transporter protein that is made primarily in the kidneys. These defects prevent proper reabsorption of basic, or positively charged amino acids such as histidine, lysine, ornithine, arginine and cysteine.[2]

Normally this protein allows certain amino acids, including cysteine, to be reabsorbed into the blood from the filtered fluid that will become urine. Mutations in either of these genes disrupt the ability of this transporter protein to reabsorb these amino acids, allowing them to become concentrated in the urine. As the levels of cysteine in the urine increase, the crystals typical of cystinuria are able to form, resulting in kidney stones. Cystine crystals form hexagonal-shaped crystals which can be viewed upon microscopic analysis of the urine. The other amino acids that are not reabsorbed do not create crystals in urine. The disorder affects 1 in 10,000 people, making it the most common genetic error of amino acid transport. Cystinuria is inherited in an autosomal recessive pattern.

Treatment

The initial treatment is with adequate hydration, alkalinization of the urine and dietary modification. If this fails then patients are usually commenced on chelation therapy such as penicillamine[3][4]

Occurrence in animals

This disease is known to occur in at least three mammalian species. These are: humans, domestic dogs canines, and a wild canid, the Maned Wolf of South America. Cystine uroliths have been demonstrated, most usually in male dogs, from approximately 70 breeds including the Australian cattle dog, Australian shepherd, Basenji, Basset, Bullmastiff, Chihuahua, Scottish deerhond, Scottish terrier, Staffordshire terrier and Welsh corgi; and in both male and female Newfoundland dogs [5]

References

  1. ^ Fjellstedt E, Harnevik L, Jeppsson JO, Tiselius HG, Söderkvist P, Denneberg T (December 2003). "Urinary excretion of total cysteine and the dibasic amino acids arginine, lysine and ornithine in relation to genetic findings in patients with cystinuria treated with sulfhydryl compounds". Urological research 31 (6): 417–425. doi:10.1007/s00240-003-0366-6. PMID 14586528. 
  2. ^ Ahmed K, Dasgupta P, Khan MS (2006). "Cystine calculi: challenging group of stones". Postgraduate medical journal 82 (974): 799–801. doi:10.1136/pgmj.2005.044156. PMID 17148700. 
  3. ^ Ahmed K, Khan MS, Thomas K, Challacombe B, Bultitude M, Glass J, Tiptaft R, Dasgupta P (Mar 2008). "Management of cystinuric patients: an observational, retrospective, single-centre analysis". Urol Int. 80 (2): 141-144. PMID 18362482. 
  4. ^ Joly D, Rieu P, Méjean A, Gagnadoux MF, Daudon M, Jungers P (November 1999). "Treatment of cystinuria". Pediatr. Nephrol. 13 (9): 945–50. doi:10.1007/s004670050736. PMID 10603157. http://link.springer.de/link/service/journals/00467/bibs/9013009/90130945.htm. 
  5. ^ D Bannasch and PS Henthorn (2009). "Changing Paradigms in Diagnosis of Inherited Defects Associated with Uroliths". Veterinary Clinics of North America Small Animal Practice 39 (1): 111-125. 

See also

External links








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