At the beginning of the four chapters on phenomena, analysis, pathophysiology and
therapy of
cystinuria the essentials of the published literature are summarized. The frequency of
cystinuria is in the order of 1:10,000. Besides the
cystine lithiasis occurring in nine tenths of all
cystinuria patients neurological diseases may also be observed. All commonly applied methods to analyze
cystine detect the sum of
cystine and
cysteine.
Cystinuria is characterized by a higher
cystine excretion, up to the 100-fold of the normal. Also the concentrations of
lysine,
arginine and
ornithine in the urine of
cystinuria patients are elevated, caused by intestinal and renal transport defects. Inevitable damage of renal parenchyma by multiple operations can drastically be reduced by the
therapy with
D-penicillamine or
alpha-mercaptopropionylglycine. The disadvantages of that formation of soluble asymmetric
disulfides are the side effects, such as
nausea, gastric difficulties and
dermatosis, occurring in up to 50% of the patients. Using the especially developed method with HPLC separation and electrochemical detector with a
mercury electrode,
cystine and
cysteine are analyzed simultaneously. In the urine of healthy persons the molar concentration of
cysteine is in the same order as
cystine. But in
cystinuria the
cysteine concentration in urine is about a thousand times less than that of
cystine. These results are evidence that a shifted redox-equilibrium of
cystine-
cysteine is also typical of
cystinuria. The molar
cysteine percentage of
cysteine in healthy persons is increased from 30 to 50% by oral
ascorbic acid administration. Therefore a
vitamin C therapy for
cystinuria is developed. 31
cystinuria patients who receive 5 g of
vitamin C a day show a decrease in the
cystine concentration of about 40%. Up to now, no side effects have been observed. The most obvious sign of the positive effect of the proposed
vitamin C therapy for
cystinuria is the missing
cystine sediment in fresh urine.