Penicillamine therapy for pediatric cystinuria: experience from a cohort of American children

The genetics of cystinuria - an update and critical reevaluation

PURPOSE OF REVIEW

We aimed to critically evaluate how the establishment of genotype-based treatment for cystinuria has been hampered due to the large number of variants of unknown significance (VUS) within the disease causing genes as well as challenges in accessing a large enough sample size for systematic analysis of endpoint parameters that truly reflect disease severity. This review further discusses how to overcome these hurdles with the establishment of a cystinuria-specific refinement of the current American College of Medical Genetics and Genomics (ACMG)-criteria of variant interpretation.

RECENT FINDINGS

Novel tools such as AlphaMissense combined with the establishment of a refined ACMG criterion will play a significant role in classifying VUS within the responsible disease genes SLC3A1 (rBAT) and SLC7A9 (BAT1). This will also be essential in elucidating the role of promising candidate genes, such as SLC7A13 (AGT1), which have been derived from murine model systems and still need further research to determine if they are involved in human cystinuria.

SUMMARY

Cystinuria was one of the first disorders to receive a gene-based classification, nonetheless, the clinically actionable implications of genetic diagnostics is still minor. This is due to poorly characterized genotype-phenotype correlations which results in a lack of individualized (genotype-) based management and metaphylaxis.

Pharmacological interventions for the management of cystinuria: a systematic review

BACKGROUND

Cystinuria is a rare genetic kidney stone disease, with no cure. Current treatments involve lowering urinary cystine levels and increasing cystine solubility. This systematic review evaluates the available literature regarding non-surgical interventions for cystinuria.

METHODS

Key electronic databases were searched for studies that described the clinical management of cystinuria with high diuresis, alkalinizing agents and thiol-based drugs that were published between 2000 and 2022. Observational studies were included if they contained clinical investigation with at least one previous or current episode of cystine stones, urine cystine levels > 250 mg/L and patients being managed with urinary dilution, alkalinizing agents or other pharmacological agents. All included studies were assessed for study design, patient characteristics and outcomes. A qualitative and critical analysis was performed whereby study quality was assessed using Methodological Index for Non-Randomized Studies (MINORS). Two authors performed the quality assessment and excluded the studies with a low MINORS score.

RESULTS

Fourteen studies met the review inclusion and quality criteria. Of the fourteen studies, two reported treatment using alkalinizing agents, six reported treatment using thiol-based drugs, and six reported combination treatment using alkalinizing agents and thiol-based drugs. These studies indicated that first-line therapies, including high fluid intake and urinary alkalinization, increased urine volume to > 3 L/day and urinary pH > 7.0, and were associated with reduced urinary cystine levels and cystine stone formation. Second-line therapy with cystine-binding thiol drugs, such as tiopronin and D-penicillamine, reduced urinary cystine levels, cystine crystal volume and increased cystine solubility, resulting in decreased cystine stone formation and stone recurrence rate. Further, combined intervention with alkalinizing agents and thiol-based drugs synergistically reduced stone recurrence.

CONCLUSION

Cystinuria treatment may require a combined approach of high diuresis, alkalinization and pharmacological interventions with regular monitoring of urinary pH, cystine levels, cystine crystal volume and solubility. However, poor adherence to treatment is relatively frequent, hence the pressing urgency for improved therapies and treatments.

The antioxidant l-Ergothioneine prevents cystine lithiasis in the Slc7a9-/- mouse model of cystinuria

The high recurrence rate of cystine lithiasis observed in cystinuria patients highlights the need for new therapeutic options to address this chronic disease. There is growing evidence of an antioxidant defect in cystinuria, which has led to test antioxidant molecules as new therapeutic approaches. In this study, the antioxidant l-Ergothioneine was evaluated, at two different doses, as a preventive and long-term treatment for cystinuria in the Slc7a9-/- mouse model. l-Ergothioneine treatments decreased the rate of stone formation by more than 60% and delayed its onset in those mice that still developed calculi. Although there were no differences in metabolic parameters or urinary cystine concentration between control and treated mice, cystine solubility was increased by 50% in the urines of treated mice. We also demonstrate that l-Ergothioneine needs to be internalized by its transporter OCTN1 (Slc22a4) to be effective, as when administrated to the double mutant Slc7a9-/-Slc22a4-/- mouse model, no effect on the lithiasis phenotype was observed. In kidneys, we detected a decrease in GSH levels and an impairment of maximal mitochondrial respiratory capacity in cystinuric mice that l-Ergothioneine treatment was able to restore. Thus, l-Ergothioneine administration prevented cystine lithiasis in the Slc7a9-/- mouse model by increasing urinary cystine solubility and recovered renal GSH metabolism and mitochondrial function. These results support the need for clinical trials to test l-Ergothioneine as a new treatment for cystinuria.

A Summary of Current Guidelines and Future Directions for Medical Management and Monitoring of Patients with Cystinuria

Cystinuria is the most common genetic cause of recurrent kidney stones. As the result of a genetic defect in proximal tubular reabsorption of filtered cystine, increased urine levels of the poorly soluble amino acid result in recurrent cystine nephrolithiasis. Recurrent cystine stones not only adversely affect the quality of patients suffering from cystinuria but also may result in chronic kidney disease (CKD) from recurrent renal injury. Thus, the mainstay of medical management revolves around prevention of stones. Recently published consensus statements on guidelines for managing cystinuria were released from both the United States and Europe. The purpose of this review is to summarize guidelines for medical management of patients with cystinuria, to provide new insight into the utility and clinical significance of cystine capacity-an assay for monitoring cystinuria, and to discuss future directions for research on treatment of cystinuria. We discuss future directions, including the potential use of cystine mimetics, gene therapy, V2-receptor blockers, and SGLT2 inhibitors, topics which have not appeared in more recent reviews. It is notable that in the absence of randomized, controlled trials, the recommendations cited here and in the guidelines are based on our best understanding of the disorder's pathophysiology, observational studies, and clinical experience.

Safety profile of D-penicillamine: a comprehensive pharmacovigilance analysis by FDA adverse event reporting system

BACKGROUND

D-penicillamine (D-pen) is a copper-chelating drug and has immune-modulatory properties. D-pen is used to treat rheumatoid arthritis, Wilson's disease, and kidney stones (cystinuria). However, associated adverse events (AEs) of D-pen treatment are frequent and often serious. Therefore, a comprehensive assessment of the safety profile of D-pen is urgently needed.

RESEARCH DESIGN AND METHODS

We identified and analyzed AEs associated with D-pen between April-1970 to July-2020 from the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) databases and calculated the reported odds ratio (ROR) with 95% confidence intervals (CI) using the disproportionality analysis.

RESULTS

A total of 9,150,234 AEs related to drugs were reported in the FAERS database, of which 542 were related to D-Pen. We report that D-pen was associated with dystonia (ROR: 20.52; 95%CI: 12.46-33.80), drug hypersensitivity (ROR: 5.42; 95%CI: 3.72-7.90), pancytopenia (ROR: 10.20; 95%CI: 5.61-18.56), joint swelling (ROR: 9.07; 95%CI: 5.51-14.94), renal-impairment (ROR: 6.68; 95%CI: 3.67-12.15), dysphagia (ROR: 5.05; 95%CI: 2.76-8.89), aggravation of condition (ROR: 4.16; 95%CI: 2.60-6.67), congestive cardiac failure (ROR: 4.04; 95%CI: 2.22-7.35), peripheral edema (ROR: 3.77; 95%CI: 2.17-6.55), tremor (ROR: 3.46; 95%CI: 2.00-6.01), pyrexia (ROR: 3.46; 95%CI: 2.00-6.01), and gait disturbance (ROR: 2.41; 95%CI: 1.29-4.52).

CONCLUSIONS

Patients taking D-pen require close monitoring of renal function, blood counts, immunity, liver, cardiac function, and neurological function. D-pen suppresses immune system which maximizes the risk of infection.

[Cystinuria]

Cystinuria is the most common monogenic nephrolithiasis disorder. Because of its poor solubility at a typical urine pH of less than 7, cystine excretion results in recurrent urinary cystine stone formation. A high prevalence of high blood pressure and of chronic kidney disease has been reported in these patients. Alkaline hyperdiuresis remains the cornerstone of the preventive medical treatment. To reach a urine pH between 7.5 and 8 and a urine specific gravity less than or equal to 1.005 should be the goal of medical treatment. D-penicillamine and tiopronin, two cysteine-binding thiol agents, should be considered as second line treatments with frequent adverse events that should be closely monitored.

Update on cystine stones: current and future concepts in treatment

Cystine stones are relatively uncommon compared with other stone compositions, constituting just 1% to 2% of adult urinary tract stone diseases, and accounting for up to 10% of pediatric stone diseases. Two responsible genes of cystinuria have been identified, the SLC3A1 and the SLC7A9. Cystinuria is diagnosed by family history, stone analysis, or by measurement of urine cystine excretion. Current treatments for cystinuria include increased fluid intake to increase cystine solubility by maintaining daily urine volume of greater than 3 Liter (L). Limiting sodium and protein intake can decrease cystine excretion. When conservative therapy fails, then pharmacologic therapy may be effective. Alkaline urine pH in the 7.0-7.5 range will reduce cystine solubility and can be achieved by the addition of alkali therapy. If these measures fail, cystine-binding thiol drugs such as tiopronin and D-penicillamine are considered. These compounds bind cysteine and prevent the formation of less soluble cystine. These drugs, however, have poor patient compliance due to adverse effects. Captopril can be useful in the treatment of cystine stones but the drug has not been tested in rigorous clinical trials. Novel potential therapies such as alpha-lipoic acid and crystal growth inhibitors (L-cystine dimethyl ester (L-CDME) and L-cystine methyl ester (L-CME)) were developed and tested in animals. Those therapies showed promising results. Compliance with treatment was associated with a lower rate of cystine stone formation.

The effect of additional drug therapy as metaphylaxis in patients with cystinuria: a systematic review

INTRODUCTION

To systematically review the effect of additional drug therapy as metaphylaxis in patients with cystinuria.

EVIDENCE ACQUISITION

A literature search of three databases (MEDLINE, Embase and the Cochrane Library) was performed according to the PRISMA-guidelines enclosing articles published up to May 2019. A total of 1117 articles were screened. Thirty-four publications met the inclusion criteria for this review.

EVIDENCE SYNTHESIS

Male-female ratio in the studied cohorts was 49.9% - 50.1%. The majority of studies showed a positive effect in reducing stone events and/or urinary cystine excretion. D-Penicillamine showed success in 13/14 (92%) studies, whereas Tiopronin-treatment showed a reduction in all (8/8; 100%) studies. All studies on Captopril (4/4) showed a decrease, however not all significant. The same is true for studies on Thiols in combination with Captopril (2/2). Furthermore, Tiopronin showed less side effects compared to D-penicillamine, respectively 30% and 37%. Captopril showed the least adverse events, with one event in nine patients.

CONCLUSIONS

The evidence on benefit of additional drug therapy in patients with cystinuria is scarce. All studied medications showed an effect on stone event and urinary cystine excretion, when used in addition to hyperhydration, alkalization and a diet low on methionine. Based on this systematic review, no drug can be preferred over another. An important aspect in the choice of drug is the risk of side effects. Therefore, the choice of additional drug should be personalized for every patient where the risk of side effects should be taken into consideration.

Amino Acid Transport Defects in Human Inherited Metabolic Disorders

Amino acid transporters play very important roles in nutrient uptake, neurotransmitter recycling, protein synthesis, gene expression, cell redox balance, cell signaling, and regulation of cell volume. With regard to transporters that are closely connected to metabolism, amino acid transporter-associated diseases are linked to metabolic disorders, particularly when they involve different organs, cell types, or cell compartments. To date, 65 different human solute carrier (SLC) families and more than 400 transporter genes have been identified, including 11 that are known to include amino acid transporters. This review intends to summarize and update all the conditions in which a strong association has been found between an amino acid transporter and an inherited metabolic disorder. Many of these inherited disorders have been identified in recent years. In this work, the physiological functions of amino acid transporters will be described by the inherited diseases that arise from transporter impairment. The pathogenesis, clinical phenotype, laboratory findings, diagnosis, genetics, and treatment of these disorders are also briefly described. Appropriate clinical and diagnostic characterization of the underlying molecular defect may give patients the opportunity to avail themselves of appropriate therapeutic options in the future.

Adverse events associated with currently used medical treatments for cystinuria and treatment goals: results from a series of 442 patients in France

OBJECTIVE

To evaluate medical treatments, in terms of adverse events (AEs) and therapeutic goals, in a large series of patients with cystinuria.

PATIENTS AND METHODS

Data from 442 patients with cystinuria were recorded retrospectively. Crystalluria was studied in 89 patients. A mixed-effects logistic regression model was used to estimate how urine pH, specific gravity and cysteine-binding thiols (CBT) correlate with risk of cystine crystalluria.

RESULTS

Alkalizing agents and CBT agents were given to 88.8% (n = 381) and 55.3% (n = 238) of patients, respectively. Gastrointestinal AEs were reported in 12.3%, 10.4% and 2.6% of patients treated with potassium bicarbonate, potassium citrate and sodium bicarbonate, respectively (P = 0.008). The percentages of patients who experienced at least one AE with tiopronin (24.6%) and with D-penicillamine (29.5%) were similar (P = 0.45). Increasing urine pH and decreasing urine specific gravity significantly reduced the risk of cystine crystalluria, whereas D-penicillamine and tiopronin treatments did not reduce this risk (odds ratio [OR] 1 for pH ≤6.5; OR 0.52 [95% confidence interval {95% CI} 0.28-0.95] for 7.0 <pH ≤7.5, P = 0.03; OR 0.26 [95% CI 0.13-0.53] for 7.5 < pH ≤8.0, P <0.001; OR 1 for specific gravity ≤1.005 OR 5.76 [95% CI 1.45-22.85] for 1.006 ≤ specific gravity ≤1.010, P = 0.01; and OR 11.06 [95% CI 2.76-44.26] for 1.011 ≤ specific gravity ≤ 1.014, P < 0.001). Increased urine pH significantly increased the risk of calcium phosphate crystalluria (OR 1 for pH≤ 6.5; OR 6.09 [95% CI 2.15-17.25] for pH >8.0, P <0.001).

CONCLUSION

Adverse events were frequent with D-penicillamine and tiopronin. Alkaline hyperdiuresis was well tolerated and reduced cystine crystalluria. Urine specific gravity ≤1.005 and urine pH >7.5, while warning about calcium-phosphate crystallization, should be the goals of medical therapy.

Cystinuria: genetic aspects, mouse models, and a new approach to therapy

Cystinuria, a genetic disorder of cystine transport, is characterized by excessive excretion of cystine in the urine and recurrent cystine stones in the kidneys and, to a lesser extent, in the bladder. Males generally are more severely affected than females. The disorder may lead to chronic kidney disease in many patients. The cystine transporter (b^0,+) is a heterodimer consisting of the rBAT (encoded by SLC3A1) and b^0,+AT (encoded by SLC7A9) subunits joined by a disulfide bridge. The molecular basis of cystinuria is known in great detail, and this information is now being used to define genotype-phenotype correlations. Current treatments for cystinuria include increased fluid intake to increase cystine solubility and the administration of thiol drugs for more severe cases. These drugs, however, have poor patient compliance due to adverse effects. Thus, there is a need to reduce or eliminate the risks associated with therapy for cystinuria. Four mouse models for cystinuria have been described and these models provide a resource for evaluating the safety and efficacy of new therapies for cystinuria. We are evaluating a new approach for the treatment of cystine stones based on the inhibition of cystine crystal growth by cystine analogs. Our ongoing studies indicate that cystine diamides are effective in preventing cystine stone formation in the Slc3a1 knockout mouse model for cystinuria. In addition to crystal growth, crystal aggregation is required for stone formation. Male and female mice with cystinuria have comparable levels of crystalluria, but very few female mice form stones. The identification of factors that inhibit cystine crystal aggregation in female mice may provide insight into the gender difference in disease severity in patients with cystinuria.

Medical therapy for nephrolithiasis: State of the art

The prevalence of nephrolithiasis is increasing worldwide. Understanding and implementing medical therapies for kidney stone prevention are critical to prevent recurrences and decrease the economic burden of this condition. Dietary and pharmacologic therapies require understanding on the part of the patient and the prescribing practitioner in order to promote compliance. Insights into occupational exposures and antibiotic use may help uncover individual risk factors. Follow-up is essential to assess response to treatment and to modify treatment plans to maximize therapeutic benefit.

Novel cystine ester mimics for the treatment of cystinuria-induced urolithiasis in a knockout mouse model

OBJECTIVE

To assess the effectiveness of l-cystine dimethyl ester (CDME), an inhibitor of cystine crystal growth, for the treatment of cystine urolithiasis in an Slc3a1 knockout mouse model of cystinuria.

MATERIALS AND METHODS

CDME (200 μg per mouse) or water was delivered by gavage daily for 4 weeks. Higher doses by gavage or in the water supply were administered to assess organ toxicity. Urinary amino acids and cystine stones were analyzed to assess drug efficacy using several analytical methods.

RESULTS

Treatment with CDME led to a significant decrease in stone size compared with that of the water group (P = .0002), but the number of stones was greater (P = .005). The change in stone size distribution between the 2 groups was evident by micro computed tomography. Overall, cystine excretion in urine was the same between the 2 groups (P = .23), indicating that CDME did not interfere with cystine metabolism. Scanning electron microscopy analysis of cystine stones from the CDME group demonstrated a change in crystal habit, with numerous small crystals. l-cysteine methyl ester was detected by ultra-performance liquid chromatography-mass spectrometer in stones from the CDME group only, indicating that a CDME metabolite was incorporated into the crystal structure. No pathologic changes were observed at the doses tested.

CONCLUSION

These data demonstrate that CDME promotes formation of small stones but does not prevent stone formation, consistent with the hypothesis that CDME inhibits cystine crystal growth. Combined with the lack of observed adverse effects, our findings support the use of CDME as a viable treatment for cystine urolithiasis.

The effect of prophylactic treatment with Shohl's solution in children with cystinuria

OBJECTIVE

To investigate the effect of prophylactic treatment with Shohl's solution on the rates of stone recurrence in paediatric patients with cystinuria.

PATIENTS AND METHODS

Between June 2007 and October 2011, 185 patients aged 16 years and younger whose stones had been completely removed by percutaneous nephrolithotomy (PCNL) were assessed for metabolic risk factors. Seventeen (9%) patients with positive cyanide-nitroprusside tests (CNT) and cystine stones enrolled in this study, and a Shohl's solution was used for alkalinisation. The patients were followed up for a mean period of two years for stone recurrence.

RESULTS

Of the patients, 10 (59%) were male, and 7 (41%) were female (p = 0.13). Twelve patients (70.5%) continued to receive medical prophylaxis regularly, whereas 5 (29.5%) patients did not. The mean pre-treatment and post-treatment urinary pH values were 5.8 ± 0.5 (5-7) and 7.5 ± 0.4 (6.5-8), respectively (p < 0.001). The pre-treatment and post-treatment specific gravities of the urine were 1021.5 ± 5.4 (1010-1030) and 1006 ± 2.3 (1004-1015), respectively (p < 0.001). The rates of recurrence were 16.6% among those who continued prophylaxis and 100% among those who did not receive prophylaxis (p = 0.001). The most common combination of metabolic anomalies was cystinuria and hypocitraturia (p < 0.001).

CONCLUSIONS

This study demonstrated that detailed clinical and laboratory evaluations should be performed for all children with cystine stone disease, and, appropriate prophylactic treatment should be recommended to prevent the reformation of stones.

D-Penicillamine targets metastatic melanoma cells with induction of the unfolded protein response (UPR) and Noxa (PMAIP1)-dependent mitochondrial apoptosis

D-Penicillamine (3,3-dimethyl-D-cysteine; DP) is an FDA-approved redox-active D-cysteine-derivative with antioxidant, disulfide-reducing, and metal chelating properties used therapeutically for the control of copper-related pathology in Wilson's disease and reductive cystine-solubilization in cystinuria. Based on the established sensitivity of metastatic melanoma cells to pharmacological modulation of cellular oxidative stress, we tested feasibility of using DP for chemotherapeutic intervention targeting human A375 melanoma cells in vitro and in vivo. DP treatment induced caspase-dependent cell death in cultured human metastatic melanoma cells (A375, G361) without compromising viability of primary epidermal melanocytes, an effect not observed with the thiol-antioxidants N-acetyl-L-cysteine (NAC) and dithiothreitol. Focused gene expression array analysis followed by immunoblot detection revealed that DP rapidly activates the cytotoxic unfolded protein response (UPR; involving phospho-PERK, phospho-eIF2α, Grp78, CHOP, and Hsp70) and the mitochondrial pathway of apoptosis with p53 upregulation and modulation of Bcl-2 family members (involving Noxa, Mcl-1, and Bcl-2). DP (but not NAC) induced oxidative stress with early impairment of glutathione homeostasis and mitochondrial transmembrane potential. SiRNA-based antagonism of PMAIP1 expression blocked DP-induced upregulation of the proapoptotic BH3-only effector Noxa and prevented downregulation of the Noxa-antagonist Mcl-1, rescuing melanoma cells from DP-induced apoptosis. Intraperitoneal administration of DP displayed significant antimelanoma activity in a murine A375 xenograft model. It remains to be seen if melanoma cell-directed induction of UPR and apoptosis using DP or improved DP-derivatives can be harnessed for future chemotherapeutic intervention.

Cystic kidney disease in a patient with systemic toxicity from long-term D-penicillamine use

D-penicillamine, used to treat cystinuria, is known to cause impaired collagen deposition and dysfunction in elastic fibers. D-penicillamine also has been associated with glomerular abnormalities, typically membranous glomerulonephritis. We describe a patient with severe bilateral cystic kidney disease that developed after long-term D-penicillamine use for treatment of cystinuria. The cysts in the kidneys were noted during an evaluation for acute kidney injury. The patient had no evidence of cysts on prior renal imaging at a time when his kidney function was normal. Simultaneously, he presented with multiorgan manifestations of D-penicillamine toxicity, including the skin findings of cutix laxa and elastosis perforans serpiginosa. Consequently, D-penicillamine treatment was discontinued, after which the progression of cystic kidney disease gradually ceased, along with the other systemic manifestations of toxicity. To our knowledge, this is the first report of cystic kidney disease associated with and perhaps caused by long-term d-penicillamine therapy. The proposed mechanism of cyst formation is the malfunction of the extracellular matrix of the kidney by d-penicillamine that leads to an impaired repair process after kidney injury.

The Interaction of thiol drugs and urine pH in the treatment of cystinuria

PURPOSE

Pharmacological therapy for cystinuria consists of alkali salts to increase urine pH and thiol drugs to form soluble cysteine-drug complexes. The effect of alkalinizing urine on thiol drug activity has not been well studied.

MATERIALS AND METHODS

Urine samples were obtained from 5 healthy subjects and pH was adjusted (range 6.0 to 8.0) in each urine aliquot. Urine samples were incubated with cystine crystals at 37C for 5, 15 and 60 minutes, and 48 hours. We compared cystine solubility in urine samples spiked with thiol drugs at a final concentration of 2 mM to that in control urine samples at the various pH levels and time points.

RESULTS

In samples incubated for 48 hours, which is the standard time frame for solubility studies, cystine solubility more than doubled with thiol drugs compared to control and did not depend on pH. However, when incubation time was shortened to 5 minutes, representing the dwell time of urine in the renal pelvis, the effect of thiol drugs to solubilize cystine greatly depended on urine pH with less cystine dissolved at lower pH.

CONCLUSIONS

Increasing urine pH greatly increased the efficacy of thiol drugs to solubilize cystine in a clinically relevant time frame. These findings suggest that to maximize the benefit of thiol drugs alkali therapy should be used in conjunction with thiol drugs with the goal of keeping urine pH at 7.5 or above. Clinical trials are needed to confirm these in vitro findings.

Cystinuria: mechanisms and management

Cystinuria is a relatively uncommon cause of pediatric stone disease, but has significant morbidity if not properly controlled because of its significant stone recurrence rate. Cystinuria is caused by the inability of the renal tubules to reabsorb filtered cystine, which is poorly soluble at a typical urine pH <7. Although many advances have been made in the understanding of the genetic and physiological basis of cystinuria, the cornerstones of treatment still involve stone prevention with dietary measures and pharmacological therapy, coupled with surgical interventions for stone removal. Pharmacological treatments can carry significant side effects that must be monitored and can limit therapy as well as impede compliance. Most patients will require surgical intervention for stone removal, although compliance with prevention strategies reduces the need for intervention.

[Cystinuria in children: A report of 4 cases]

Cystinuria is an inherited autosomal-recessive disorder of renal reabsorption of the dibasic amino acids. It is the cause of about 6% of all kidney stones observed in children. Cystine is relatively insoluble at the physiological pH of urine. Cystine stones are characteristic and frequent recurrences are observed. We report on 4 cases and describe the initial presentation (obstructive renal failure, urinary sepsis, familial screening) and the medical and surgical management. Medical management is mainly based on hyperhydration and urine alkalinization. Long-term therapy with sulfhydryl agents to prevent formation of renal stones seems to be effective but adverse side effects are frequent, requiring the withdrawal of treatment. Urological management has evolved from surgical stone removal to minimally invasive procedures (extracorporeal shock wave lithotripsy, ureteroscopy).

New horizons in the management of patients with cystinuria

PURPOSE OF REVIEW

Although the formation of cystine stones is seen in only a small fraction of all patients with urolithiasis, this disease is associated with a pronounced morbidity. The difficult clinical management of these patients, with the aim of arresting or decreasing the rate of recurrent stone formation, is well recognized. This review summarizes some recent knowledge.

RECENT FINDINGS

An early and correct diagnosis of cystinuria is fundamental for a successful course of the disease in these patients. Formation starts early in life, and attention to this diagnosis is necessary for the paediatric stone formers. New radiological and biochemical improvements seem useful in this respect. A combination of medical tools is usually necessary to influence the very often, troublesome stone-forming activity. Urine dilution, alkalization and chelating therapy have remained the cornerstones of the therapeutic approach. The importance of a high urine pH has been further emphasized, and the possibility to use acetazolamide is a promising improvement of the medical treatment. In order to increase the compliance and reduce the need of active stone removal, special stone clinics seem to be of particular value. The understanding of the genetic background might open future treatment alternatives.

SUMMARY

Patients afflicted by cystine stone disease need an aggressive medical treatment, gentle stone-removing surgery and careful follow-up.