Cystinuria

The Cystinuria is a hereditary defect in the renal tubules, wherein the absorption of the amino acid cystine and impaired urinary excretion is increased and may form cystine stones in the urinary tract. Symptoms can also be kidney failure renal colic, urinary tract infections or as a consequence. Diagnosis is Zystinausscheidung is measured in the urine. The treatment of choice is a alkalinization of urine and increased fluid intake.

Cystinuria was classified initially by the excretion of urinary cystine and dibasic amino acids “in obligate carriers”. In this classification, parents of the affected children were classified as either normal (Type I), medium (type III) or significant (type II) increases in cystine excretion.

The Cystinuria is a hereditary defect in the renal tubules, wherein the absorption of the amino acid cystine and impaired urinary excretion is increased and may form cystine stones in the urinary tract. Symptoms can also be kidney failure renal colic, urinary tract infections or as a consequence. Diagnosis is Zystinausscheidung is measured in the urine. The treatment of choice is a alkalinization of urine and increased fluid intake. Cystinuria was classified initially by the excretion of urinary cystine and dibasic amino acids “in obligate carriers”. In this classification, parents of the affected children were classified as either normal (Type I), medium (type III) or significant (type II) increases in cystine excretion. A more recent classification is based on the genotype: patients of type A have homozygous mutations in the gene SLC3A1 and type B patients have homozygous mutations in SLC7A9. These genes encode proteins, which together form a heterodimer, which is responsible for cystine and dibasic amino acid transport in the proximal tubule. Cystinuria should not be confused with cystinosis (Fanconi syndrome: hereditary conditional Fanconi syndrome). Pathophysiology The primary defect leads to decreased renal proximal tubular reabsorption of cystine and increased renal cystine concentration. Cystine is hardly soluble in acidic urine; exceeds its concentration in urine solubility, cystine forms in the urinary tract crystal condensate and zystine kidney stones. The absorption of other dibasic amino acids (lysine, ornithine, arginine) is likewise reduced. This is problematic because these amino acids using an independent from Zystintransport transport system. As the dibasic amino acids in urine are more soluble than cystine, excretion does not lead to precipitation and stone formation. Their absorption and cystine are also limited in the small intestine. Symptoms and signs The symptoms usually renal colic, occur between 10 and 30 years. Urinary tract infections and kidney failure due to urinary tract obstruction can develop as a result. Diagnostics Microscopic examination of urinary sediment measurement of Zystinausscheidung in the urine analysis of collected kidney stones radiopacity cystine stones form in the renal pelvis or in the bladder. Ausgusssteine ??are common. Cystine can occur in urine in the form of yellow-brown, hexagonal crystals that are diagnostic. With the nitroprusside cyanide test the increased cystine can be detected in urine. Quantitative Zystinausscheidung is usually> 400 mg / day in cystinuria (normal is <30 mg / day). Treatment High fluid intake alkalinization of urine sodium restriction in diet protein diet arms (if possible) A stage renal disease can develop. The reduction of Zystinausscheidung in urine reduces the renal toxicity, and is achieved by increasing the volume of urine with a sufficient liquid supply to ensure a urine flow of 3-4 l / day. even at night, when the urine pH drops. Alkalization of the urine to a pH of> 7.0 by the administration of potassium citrate or potassium bicarbonate 1 meq / kg p.o. 3- or 4 times a day and in some cases Acetolamid 5 mg / kg (up to 250 mg) p.o. at bedtime the solubility of cystine increases significantly. A slight limitation of the salt content in the diet (100 mmol / day) and the protein content (0.8-1.0 g / kg / day) may help to reduce cystine excretion. If the increased hydration and alkalization can not prevent the stone formation, other medicines penicillamine can sometimes (4 times 7.5 mg / kg four times a day for infants and 125 mg-0.5 g po daily for older children) improves solubility of cystine. The therapeutic use is limited but because of its toxicity. About half of patients develop signs of toxicity such as fever, rash, arthritis or less frequently nephrotic syndrome, pancytopenia or lupus-like reaction. Pyridoxine doses (50 mg po once daily) should be taken with penicillamine. Tiopronin (100-300 mg po 4 times daily) can be given instead of penicillamine to treat some children because it rarely causes side effects. Captopril (0.3 mg / kg p.o. 3 times a day) is not as effective as penicillamine, but but less toxic. Close monitoring of therapeutic success is very important. Important points defects of Urinresorption of cystine increase the cystine in the urine, resulting in cystine kidney stones and sometimes chronic kidney disease. Yellow-brown hexagonal crystals in the urine are pathognomonic; quantitative Zystinausscheidung is usually> 400 mg / day. The treatment consists in an increased fluid intake, in order to achieve urinary excretion 3-4 l / day, and the urine is alkalized with potassium citrate or potassium bicarbonate. The intake of sodium and protein through diet is restricted. Drugs such as penicillamine, Tiopronin or captopril may be required, but their side effects can take care of concerns.

Health Life Media Team

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