[Long-term study of tiopronin in patients with cystinuria]

Thirty two patients with cystinuria were enrolled in this long-term study and 16 patients were treated with tiopronin for 24 weeks. Tiopronin reduced daily urinary cystine excretion from 901.48 mg (before treatment) to 488.60 mg (on the average of 12th week and 24th week after tiopronin administration) successfully. Tiopronin therapy was tolerated well, but side effects were observed in 13 events in 6 patients. Thus tiopronin was expected to be effective in preventing cystine stone formation and tolerated well.

Treatment of cystinuria

Cystine urolithiasis is the only clinical expression of cystinuria, an autosomal recessive genetic defect of the transepithelial transport of cystine and other dibasic amino acids in the kidney. Stones form due to the increased excretion of cystine, which is poorly soluble at normal urine pH. Cystine stones are often resistant to extracorporeal shock wave lithotripsy, so that percutaneous surgery or ureteroscopy are the preferred techniques of stone extraction. Medical preventative treatment is based on high diuresis (>/=1.5 l/m(2) per day) well distributed throughout the day and night, and urine alkalinization up to pH 7.5 by means of sodium bicarbonate and/or potassium citrate. When these basal measures are ineffective at preventing stone recurrence or dissolving pre-existing stones, sulfhydryl agents such as D-penicillamine or tiopronin, which form highly soluble mixed disulfides with cystine moieties, are to be added to urine dilution and alkalinization, especially when cystine excretion is in excess of 750 mg/day (3 mmol/day). Frequent clinical and ultrasound follow-up is needed to encourage patient compliance and assess efficacy and tolerance of treatment.

[Urologic management of cystine lithiasis in the upper urinary tract. Modalities and indications]

Cystine urinary stones is a relatively rare hereditary disorder of dibasic amino acid transport characterized by frequent recurrences. The management of these stones remains problematical despite the remarkable progress in the urological treatment of upper urinary tract stones. Cystine stones are particularly refractory to extracorporeal shock waves and relatively inaccessible to dye pulsed laser (504 nm). Apart from this exception, endourological techniques often represent the most appropriate therapeutic solution, but they are associated with significant morbidity. The physicochemical characteristics of these stones also allow dissolution by urinary alkalinization or the formation of disulfide compounds. In parallel with oral treatments, which constitute the basis of prevention of recurrence, dissolution can be obtained by direct perfusion of the urinary tract. This approach often requires irrigation for several weeks with a risk of the specific complications of catheterization, especially percutaneous catheterization. Prophylaxis, essentially consisting of dilution and dissolution of urinary cystine, raises the problem of the potential adverse effects of drug treatment. Cystinuria is easily detectable and can be investigated either systematically or only in the families concerned. However, the incidence as well as the frequently benign nature of cystinuria tend to limit its value and its indications.

Investigations on the early diagnosis of cystinuria in children

The procedure described confirms that the Ni2+/S2O4(2-) tablet test is a suitable quick cystine screening test for large groups. In 16 (0.67%) of 2,395 one- to three-year-old crèche children significantly enhanced cystine levels of 0.60-0.96 mmol/l were found. The corresponding creatinine values (mmol/l) did not reveal any significant deviations from the normal values. In a preliminary group of 9 children, enhanced lysine levels support the suspicion of the existence of cystinuria without clinical symptoms. This also forms the basis for further necessary family histories as well as for prophylactic measures.

Urine screening for aminoacidopathies: is it beneficial? Results of a long-term follow-up of cases detected bny screening one millon babies

One million 6-week-old infants were screened for aminoacidurias and the long-term follow-up analyzed to assess the benefits of the screening program. Apart from phenylketonuria, now normally detected by blood screening at five days, the most frequent abnormalities identified were cystinuria, histidinemia, Hartnup disease, and iminoglycinuria. Other disorders occurred less frequently than 1:100,000. Early diagnosis provided unequivocal clinical benefit only for phenylketonuria. There was probable benefit to patients with cystinuria, homocystinuria, argininosuccinic aciduria, and to some patients with Hartnup disease. However, benefit of early diagnosis in these disorders, of which the combined incidence was 1:10,000, was not clear-cut; for example, in 68 cystinuric children, four had already developed renal stones despite close medical supervision and a regimen of increased fluid intake to the limits of tolerance. No patient detected with any other condition benefited, either because the condition appeared benign and was not treated, or because the disorder was serious or lethal and there was a bad outcome despite early diagnosis and treatment. Existing urine screening programs should explore the incidence and clinical significance of further biochemical abnormalities detectable in the newborn infant, but there is no indication at present for the initiation of new urine screening programs designed to detect only aminoacidurias.