Plasma chitotriosidase enzyme activity as a novel therapeutic monitor for cysteamine treatment in nephropathic cystinosis: A retrospective validation study.

BACKGROUND: Cystine-depleting therapy in nephropathic cystinosis is currently monitored via the white blood cell cystine assay, although its application and usefulness are limited by practical and technical issues. Therefore, alternative biomarkers that are widely available, more economical and less technically demanding, while reliably reflecting long-term adherence to cysteamine treatment, are desirable. Recently, we proposed chitotriosidase enzyme activity as a potential novel biomarker for the therapeutic monitoring of cysteamine treatment in cystinosis. In this study, we aimed to validate our previous findings and to confirm the value of chitotriosidase in the management of cystinosis therapy. MATERIALS & METHODS: A retrospective study was conducted on 12 patients treated at the National Institutes of Health Clinical Center and followed up for at least 2 years. Plasma chitotriosidase enzyme activity was correlated with corresponding clinical and biochemical data. RESULTS: Plasma chitotriosidase enzyme activity significantly correlated with WBC cystine levels, cysteamine total daily dosage and a Composite compliance score. Moreover, plasma chitotriosidase was a significant independent predictor for WBC cystine levels, and cut-off values were established in both non-kidney transplanted and kidney transplanted cystinosis patients to distinguish patients with a good versus poor compliance with cysteamine treatment. Our observations are consistent with those of our previous study and validate our findings. CONCLUSIONS: Chitotriosidase enzyme activity is a valid potential alternative biomarker for monitoring cysteamine treatment in nephropathic cystinosis patients. SYNOPSIS: Chitotriosidase enzyme activity is a valid potential alternative biomarker for monitoring cysteamine treatment in nephropathic cystinosis patients.

Muscle and Bone Impairment in Infantile Nephropathic Cystinosis: New Concepts.

Cystinosis Metabolic Bone Disease (CMBD) has emerged during the last decade as a well-recognized, long-term complication in patients suffering from infantile nephropathic cystinosis (INC), resulting in significant morbidity and impaired quality of life in teenagers and adults with INC. Its underlying pathophysiology is complex and multifactorial, associating complementary, albeit distinct entities, in addition to ordinary mineral and bone disorders observed in other types of chronic kidney disease. Amongst these long-term consequences are renal Fanconi syndrome, hypophosphatemic rickets, malnutrition, hormonal abnormalities, muscular impairment, and intrinsic cellular bone defects in bone cells, due to CTNS mutations. Recent research data in the field have demonstrated abnormal mineral regulation, intrinsic bone defects, cysteamine toxicity, muscle wasting and, likely interleukin-1-driven inflammation in the setting of CMBD. Here we summarize these new pathophysiological deregulations and discuss the crucial interplay between bone and muscle in INC. In future, vitamin D and/or biotherapies targeting the IL1ß pathway may improve muscle wasting and subsequently CMBD, but this remains to be proven.

Fertility in Cystinosis.

Cystinosis is a rare inheritable lysosomal storage disorder characterized by cystine accumulation throughout the body, chronic kidney disease necessitating renal replacement therapy mostly during adolescence, and multiple extra-renal complications. The majority of male cystinosis patients are infertile due to azoospermia, in contrast to female patients who are fertile. Over recent decades, the fertility status of male patients has evolved from a primary hypogonadism in the era before the systematic treatment with cysteamine to azoospermia in the majority of cysteamine-treated infantile cystinosis patients. In this review, we provide a state-of-the-art overview on the available clinical, histopathological, animal, and in vitro data. We summarize current insights on both cystinosis males and females, and their clinical implications including the potential effect of cysteamine on fertility. In addition, we identify the remaining challenges and areas for future research.

Chitotriosidase as a Novel Biomarker for Therapeutic Monitoring of Nephropathic Cystinosis.

BACKGROUND: Nephropathic cystinosis, a hereditary lysosomal storage disorder caused by dysfunction of the lysosomal cotransporter cystinosin, leads to cystine accumulation and cellular damage in various organs, particularly in the kidney. Close therapeutic monitoring of cysteamine, the only available disease-modifying treatment, is recommended. White blood cell cystine concentration is the current gold standard for therapeutic monitoring, but the assay is technically demanding and is available only on a limited basis. Because macrophage-mediated inflammation plays an important role in the pathogenesis of cystinosis, biomarkers of macrophage activation could have potential for the therapeutic monitoring of cystinosis. METHODS: We conducted a 2-year prospective, longitudinal study in which 61 patients with cystinosis who were receiving cysteamine therapy were recruited from three European reference centers. Each regular care visit included measuring four biomarkers of macrophage activation: IL-1ß, IL-6, IL-18, and chitotriosidase enzyme activity. RESULTS: A multivariate linear regression analysis of the longitudinal data for 57 analyzable patients found chitotriosidase enzyme activity and IL-6 to be significant independent predictors for white blood cell cystine levels in patients of all ages with cystinosis; a receiver operating characteristic analysis ranked chitotriosidase as superior to IL-6 in distinguishing good from poor therapeutic control (on the basis of white blood cell cystine levels of <2 nmol 1/2 cystine/mg protein or ≥2 nmol 1/2 cystine/mg protein, respectively). Moreover, in patients with at least one extrarenal complication, chitotriosidase significantly correlated with the number of extrarenal complications and was superior to white blood cell cystine levels in predicting the presence of multiple extrarenal complications. CONCLUSIONS: Chitotriosidase enzyme activity holds promise as a biomarker for use in therapeutic monitoring of nephropathic cystinosis.

LC-MS/MS measurement of leukocyte cystine; effect of preanalytic factors.

Cystinosis is an autosomal recessive disorder characterized by the accumulation of cystine in lysosomes, causing irreversible damage to organs, especially the kidneys. Intracellular leukocyte cystine concentrations are used to diagnose cystinosis and to monitor cysteamine treatment. The aim of this study was to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method without derivatization capable of measuring leukocyte intracellular cystine concentrations. During development, the effects of using three different protein precipitation agents were evaluated in terms of sensitivity and the matrix effect, with 12% trichloroacetic acid providing the highest sensitivity. The effects of different blood collection tubes were also assessed in terms of recovery, matrix effect, and protein content. Compared to other methods, our method was quicker (run time of 3 min), was linear over the range 0.078-100 µM, and had lower limits of detection (0.0192 µM) and quantification (0.0582 µM). The intra-day and inter-day reproducibility %CVs were ≤10%. and the method had excellent recovery rates (94%-106%). Other parameters including matrix selectivity, injection carryover, leukocyte lysate stability were also validated and met the acceptance criterias of European Medicines Agency (EMA) Guideline. The assay was successfully applied to quantify cystine leukocyte concentration in healthy and cystinosis patients.

Diagnosis and Monitoring of Cystinosis Using Immunomagnetically Purified Granulocytes.

BACKGROUND: Cystine determination is a critical biochemical test for the diagnosis and therapeutic monitoring of the lysosomal storage disease cystinosis. The classical mixed-leukocyte cystine assay requires prompt specialized recovery/isolation following blood drawing, providing cystine concentrations normalized to total protein from assorted types of white blood cells, each with varying cystine content. METHODS: We present a new workflow for cystine determination using immunomagnetic granulocyte purification, and new reference ranges established from 47 patient and 27 obligate heterozygote samples assayed. Samples were collected in acid-citrate dextrose tubes and their stability was proven to allow for overnight shipping before analysis. Cystine was quantified by LC-MS/MS. RESULTS: The new method was reproducible (<15% root mean square error) and specific, assaying purified granulocytes from blood samples that no longer required immediate preparation and therefore allowing for up to 30 h before processing. There was a nearly a 2-fold increase in the therapeutic target (1.9 nmol half-cystine/mg protein) range, established using distributions of patient, obligate heterozygote, and control samples. The 2.5-97.5 percentile ranges (-2 SD to +2 SD around mean) for these cohorts were 0.67-6.05 nmol/mg protein for patients, 0.33-1.35 nmol/mg protein for obligate heterozygotes, and 0.09-0.35 nmol/mg protein for controls. CONCLUSIONS: The intracellular cystine determination method using immunopurified granulocytes followed by LC-MS/MS analysis improves the inherent variability of mixed leukocyte analysis and eliminates the need for immediate sample preparation following blood draw.

[COMPARISON OF FREE CARNITINE LEVELS WITH NUTRITIONAL STATUS IN INFANTILE NEPHROPATHYC CISTINOSIS PATIENTS]. / COMPARACIÓN ENTRE LOS NIVELES DE CARNITINA LIBRE Y EL ESTADO NUTRICIONAL EN PACIENTES CON CISTINOSIS NEFROPÁTICA INFANTIL.

INTRODUCTION: infantile nephropathic cystinosis (INC) is an autosomal recessive disorder that causes defects in cystine transport with subsequent accumulation in almost all body tissues, especially kidneys. There are few studies regarding the nutritional status assessment of patients with INC. It has been reported that patients with INC showed increased urinary losses of carnitine, resulting in plasma and muscle carnitine deficiency also increased metabolic requirements of carnitine in this patients have also been proposed, but to date carnitine supplementation is controversial. OBJECTIVE: the aim of this study was to compare carnitine blood concentrations with nutritional status assessed by three anthropometric parameters: body mass index, mid-upper arm circumference and tricipital skin fold in patients with INC. MATERIAL AND METHODS: anthropometric assessment of 10 patients with INC which included measurement of weight, height, mid-upper arm circumference and tricipital skin fold thickness. Free carnitine (C0) was measured by tandem mass spectrometry in fasting blood samples. RESULTS: a total of 10 patients with INC were analyzed, 5 with and 5 without renal graft. According to the body mass index, 3/10 presented malnutrition. Muscular mass was found low in 8/10 patients (3 without renal graft and all the transplanted) the mid-upper arm circumference showed correlation with C0 blood concentrations (r2 = 0.353); non transplanted patients had C0 levels significantly lower than the transplanted ones (Chi2 = 0.0027). CONCLUSION: in this study we found that 70% of patients had low C0 blood levels that had a correlation with depleted lean body mass. It is recommendable to evaluate the nutritional status of these patients as part of their routine medical evaluation.

Introducción: la cistinosis nefropática infantil (CNI) es una enfermedad genética debida a un defecto del transporte de la cistina, con la subsecuente acumulación de este aminoácido predominantemente en el riñón. Existen pocos estudios sobre la evaluación del estado nutricional en pacientes con esta patología, pero se sabe que tienen una excreción de carnitina urinaria aumentada, lo que puede dar como resultado una deficiencia plasmática y muscular de este compuesto; sin embargo, la suplementación de carnitina en CNI es controversial. Objetivo: comparar la concentración sanguínea de carnitina libre (C0) con el estado nutricional de una cohorte de pacientes con CNI. Material y métodos: evaluación antropométrica mediante la medición de peso, talla, perímetro braquial (PB) y pliegue cutáneo tricipital (PCT). La C0 se cuantificó mediante espectrometría de masas en tándem en muestras de sangre en ayuno. Resultados: se analizaron 10 pacientes con CNI, 5 con y 5 sin trasplante renal. De acuerdo con el IMC, 3/10 presentaron desnutrición. La reserva de masa magra se encontró baja en 8/10 pacientes (3 no trasplantados y todos los trasplantados). El PB mostró correlación con las concentraciones sanguíneas de C0 (r2 = 0,353); Los pacientes no trasplantados tuvieron niveles de C0 significativamente más bajos que los trasplantados (Chi2 = 0,0027). Conclusión: en esta población de pacientes con CNI se encontró un 70% de sujetos con C0 baja, que se correlaciona con la masa magra disminuida. Es recomendable hacer una evaluación nutricional de rutina que incluya los tres parámetros antropométricos como parte del seguimiento médico-nutricional integral de estos pacientes.

Cystinosis: renal glomerular and renal tubular function in relation to compliance with cystine-depleting therapy.

BACKGROUND AND OBJECTIVES: Nephropathic cystinosis is a lysosomal storage disorder characterized by renal tubular Fanconi syndrome in infancy and glomerular damage leading to renal failure at ∼10 years of age. Therapy with the cystine-depleting agent cysteamine postpones renal failure, but the degree of compliance with this treatment has not been correlated with preservation of kidney function. METHODS: We assessed leucocyte cystine depletion by cysteamine and created the composite compliance score that incorporates the extent of leucocyte cystine depletion, as well as duration of cysteamine treatment, into a single integer. Age at renal failure was used to gauge preservation of renal function, and the Fanconi syndrome index (FSI), a measure of aminoaciduria, was used to assess renal tubular Fanconi syndrome. RESULTS: Age at renal failure varied directly and linearly with the composite compliance score (y = 0.3x +8.8; R(2) = 0.61). The slope indicated that for every year of excellent cystine depletion, nearly 1 year of renal function was preserved. Age at renal failure correlated roughly with mean leucocyte cystine level, but not with mean cysteamine dosage. There was no correlation between the FSI and the composite compliance score. CONCLUSIONS: Greater compliance with oral cysteamine therapy yields greater preservation of renal glomerular, but not tubular, function. Oral cysteamine therapy should be given at the maximum tolerated dose, within the recommended limits.

Treatment of cystinosis with delayed-release cysteamine: 6-year follow-up.

BACKGROUND: Patients with nephropathic cystinosis are required to take 6-hourly immediate-release cysteamine (Cystagon®) to reduce disease progression. This arduous regimen affects quality of life, disrupts sleep, and may result in non-compliance with therapy. Enteric-coated cysteamine bitartrate (EC-cysteamine) was developed as a "proof-of-concept" formulation for twice-daily ingestion. Previous reports have shown this therapy to be effective up to a mean of 14 months. CASE-DIAGNOSIS/TREATMENT: Two subjects (aged 13 and 15 years) received EC-cysteamine for 5-6 years at 60-65 % of their previous total daily dose of immediate-release cysteamine given at 6-h intervals. White blood cell (WBC) cystine levels were monitored every 1-3 months. CONCLUSION: The administration of EC-cysteamine did not result in any change in mean trough WBC cystine levels or any deterioration in the estimated glomerular filtration rate, thyroid, or liver function, suggesting that delayed-release, twice-daily EC-cysteamine is an effective long-term treatment alternative to immediate-release cysteamine given at 6-h intervals.

[Practical markers of renal function in cystinosis patients]. / Marcadores práticos de função renal em pacientes com cistinose.

BACKGROUND: Cystinosis is an autossomic recessive systemic disease that leads to renal insufficiency early in life unless cysteamine be started early. Unfortunately, even in this situation the patients will develop chronic renal disease with need of renal replacement therapy about second decade of life. Therefore, the renal function evaluation is essential to these patients. The aim of this study was to evaluate cystatin C, serum creatinine and creatinine clearance estimated by stature (Schwartz Formula) in cystinosis patients, with different degrees of renal function, and to correlate these parameters. METHODS: We studied cystinosis patients, aged lower than 18 years, with different degrees of renal function, classified according to KDOQI in Chronic Kidney Disease stage 1 to 4. No patient was under renal replacement therapy. In these patients we evaluate the serum creatinine, cystatin C and creatinine clearance according to Schwartz Formula. RESULTS: We analyzed 103 blood samples of 26 patients. We detected a significant statistical correlation between serum creatinine and cystatin C (r = 0.81, p < 0.0001), cystatin C and creatinine clearance estimated by stature (r = -0.84, p < 0.0001) and between serum creatinine and creatinine clearance estimated by stature (r = -0.97, p < 0.0001). CONCLUSIONS: The expensive measurement of cystatin C showed no advantage in relation to serum creatinine and creatinine clearance according to Schwartz Formula in cystinosis patients to estimate the glomerular filtration rate. This is the first report checking the value of serum creatinine, creatinine clearance estimated by stature and cystatin C in cystinosis patients.

Marcadores práticos de função renal em pacientes com cistinose / Practical markers of renal function in cystinosis patients

INTRODUÇÃO: Cistinose é uma doença sistêmica, autossômica recessiva, que leva à insuficiência renal crônica na infância, a não ser que o tratamento com cisteamina seja iniciado precocemente. Mesmo nestas condições, os pacientes evoluem para doença renal crônica terminal por volta da segunda década da vida. Portanto, a avaliação da função renal é essencial neste grupo de pacientes. OBJETIVO: Avaliar e correlacionar a cistatina C, creatinina sérica e o clearance de creatinina pela Fórmula de Schwartz em pacientes com cistinose, com diferentes graus de função renal. MÉTODOS: Foram incluídos pacientes com menos de 18 anos de idade, com diferentes níveis de função renal, de acordo com o KDOQI em estágios 1 a 4. Nenhum dos pacientes estava em terapia de substituição renal. Foram medidos os seguintes parâmetros: cistatina C, creatinina sérica e o clearance de creatinina pela fórmula de Schwartz. RESULTADOS: Foram analisadas 103 amostras de sangue de 26 pacientes. Foi detectada correlação significativa entre creatinina sérica e cistatina C (r = 0,81, p < 0,0001), cistatina C e o clearance de creatinina pela fórmula de Schwartz (r = -0,84, p < 0,0001) e creatinina sérica e clearance de creatinina (r = -0,97, p < 0,0001). CONCLUSÕES: A medida da cistatina não mostrou nenhuma vantagem sobre a creatinina sérica e o clearance de creatinina pela fórmula de Schwartz em pacientes com cistinose para avaliar o ritmo de filtração glomerular. Este é o primeiro relato sobre o valor da creatinina sérica, do clearance de creatinina pela fórmula de Schwartz e da cistatina C em pacientes com cistinose.

BACKGROUND: Cystinosis is an autossomic recessive systemic disease that leads to renal insufficiency early in life unless cysteamine be started early. Unfortunately, even in this situation the patients will develop chronic renal disease with need of renal replacement therapy about second decade of life. Therefore, the renal function evaluation is essential to these patients. The aim of this study was to evaluate cystatin C, serum creatinine and creatinine clearance estimated by stature (Schwartz Formula) in cystinosis patients, with different degrees of renal function, and to correlate these parameters. METHODS: We studied cystinosis patients, aged lower than 18 years, with different degrees of renal function, classified according to KDOQI in Chronic Kidney Disease stage 1 to 4. No patient was under renal replacement therapy. In these patients we evaluate the serum creatinine, cystatin C and creatinine clearance according to Schwartz Formula. RESULTS: We analyzed 103 blood samples of 26 patients. We detected a significant statistical correlation between serum creatinine and cystatin C (r = 0.81, p < 0.0001), cystatin C and creatinine clearance estimated by stature (r = -0.84, p < 0.0001) and between serum creatinine and creatinine clearance estimated by stature (r = -0.97, p < 0.0001). CONCLUSIONS: The expensive measurement of cystatin C showed no advantage in relation to serum creatinine and creatinine clearance according to Schwartz Formula in cystinosis patients to estimate the glomerular filtration rate. This is the first report checking the value of serum creatinine, creatinine clearance estimated by stature and cystatin C in cystinosis patients.

Detailed studies of growth hormone secretion in cystinosis patients.

BACKGROUND: Cystinosis is an autosomal recessive disorder characterized by intralysosomal cystine accumulation. Growth retardation is more pronounced in cystinosis than in other chronic kidney diseases and is mostly not corrected by cysteamine. METHODS: Growth was evaluated in nine cystinosis patients, all treated with cysteamine, both after cysteamine and recombinant human growth hormone (rhGH) therapy initiation. Growth hormone (GH) secretion was studied by nocturnal GH measurements in four of nine patients and by glucagon test in four of nine patients. RESULTS: RhGH was administered to seven of nine patients. At rhGH initiation, height was below -2 SDS in five of seven patients, final height was above -2 SDS in six of seven. In two patients not treated with rhGH, final height remained below -4 SDS despite cysteamine treatment being started at the age of 6.1 and 8.1 years, respectively. Nocturnal GH secretion was normal in all patients. Glucagon tests revealed GH deficiency in one patient; two of four patients had abnormal GH peak timing. CONCLUSIONS: We present the first reported case of GH deficiency in cystinosis. Although no overt GH deficiency was detected in other patients, abnormal GH peak timing can indicate a subclinical GH secretion problem. RhGH significantly improved growth in cystinosis patients and should be initiated early in life.

Improvement in the renal prognosis in nephropathic cystinosis.

BACKGROUND AND OBJECTIVES: Nephropathic cystinosis (NC) is an autosomal recessive disorder occurring in one to two per 100,000 newborns. Because of the rarity of NC, long-term outcome data are scarce. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: 245 NC patients from 18 countries provided data to the ESPN/ERA-EDTA registry. We matched NC patients on renal replacement therapy (RRT) to non-NC children on RRT. RESULTS: Between 1979 and 2008, mean age at the start of RRT among NC children increased by 0.15 year per calendar year (95% confidence interval, 0.10 to 0.21) from 8.8 to 12.7 years, whereas we did not observe this in non-NC children. Five-year survival after the start of RRT improved in NC patients from 86.1% (before 1990) to 100% (since 2000) as compared with the control population (89.6% and 94.0%). NC patients received a renal allograft more often (relative risk, 1.09; 95% confidence interval, 1.00 to 1.17) as compared with matched RRT children, and 5-year graft survival was better (94.0% versus 84.0%). NC dialysis patients were less often hypertensive than non-NC children matched for age, country, and dialysis modality (42.7% versus 51.7%) and had lower parathyroid hormone levels (median, 56 versus 140 pg/ml). Although height at start of RRT slightly improved during the past decade, children with NC remained significantly shorter than non-NC children at the start of RRT. CONCLUSIONS: We demonstrated improved survival of the renal function as well as better patient and graft survival after the start of RRT in a large European cohort of NC patients over the last two decades.

The 57 kb deletion in cystinosis patients extends into TRPV1 causing dysregulation of transcription in peripheral blood mononuclear cells.

BACKGROUND: Cystinosis is an autosomal recessive disease characterised by the abnormal accumulation of lysosomal cystine. Mutations in the cystinosin gene (CTNS) represent known causes for the disease. The major cystinosis mutation is a 57 kb deletion on human chromosome 17p13 that removes the majority of CTNS and the entire adjacent gene, CARKL/SHPK. OBJECTIVES: In order to identify other genes that may influence the cystinosis pathobiological pathway, peripheral blood mononuclear cells (PBMC) were collected from cystinosis family members, and DNA and RNA extracted. RESULTS: Using whole genome transcriptional profiling, transient receptor potential vanilloid 1 (TRPV1) was found to be differentially expressed in association with cystinosis. This was verified using TaqMan qRT-PCR. There was a 72% reduction in PBMC TRPV1 mRNA levels in cystinosis individuals homozygous for the 57 kb deletion (n=6) compared to unaffected individuals without the deletion (n=6) (p=0.002). TRPV1 is a sensory receptor located on chromosome 17p13, adjacent to CARKL/SHPK. It was ascertained that the 57 kb deletion extends from exon 10 of CTNS, upstream through CARKL/SHPK, to intron 2 of TRPV1, thus deleting the first two non-coding exons. CONCLUSION: This is the first study to report that the 57 kb deletion extends into the TRPV1 gene causing dysregulation of transcription in PBMC isolated from cystinosis patients.

Elevated concentrations of sedoheptulose in bloodspots of patients with cystinosis caused by the 57-kb deletion: implications for diagnostics and neonatal screening.

Cystinosis is an autosomal recessive lysosomal storage disease caused by mutations in CTNS. The most prevalent CTNS mutation is a homozygous 57-kb deletion that also includes an adjacent gene named SHPK (CARKL), encoding sedoheptulokinase. Patients with this deletion have elevated urinary concentrations of sedoheptulose. Using derivatisation with pentafluorobenzyl hydroxylamine and liquid chromatography-tandem mass spectrometry (LC-MS/MS), we developed a new sensitive method for the quantification of sedoheptulose in dried blood spots. This method can be utilized as a quick screening test to detect cystinosis patients homozygous for the 57-kb deletion in CTNS; which is the most common mutation of cystinosis. Sedoheptulose concentrations in the deleted patients were 6 to 23 times above the upper limit for controls. The assessment of sedoheptulose in a bloodspot from a known cystinosis patient homozygous for the 57-kb deletion retrieved from the Dutch neonatal screening program showed that sedoheptulose was already elevated in the neonatal period. There was no overlap in sedoheptulose levels between cystinosis patients homozygous for the 57-kb deletion and cystinosis patients not homozygous for this deletion. Our presented method can be used prior to mutation analysis to detect cystinosis patients homozygous for the 57-kb deletion. We feel that the presented method enables fast (pre)-symptomatic detection of cystinosis patients homozygous for the 57-kb deletion, allowing early treatment.

Long-term treatment of cystinosis in children with twice-daily cysteamine.

OBJECTIVE: Cystinosis causes renal and other organ failure. Treatment with 6-hourly cysteamine bitartrate (Cystagon, Mylan, Morgantown, West Virginia) reduces intracellular cystine and the rate of organ deterioration. A recent study showed that an enteric-release cysteamine required less frequent daily dosing. This report describes the long-term use of enteric-coated (EC) cysteamine bitartrate (Cystagon) in children with cystinosis. STUDY DESIGN: After a pharmacokinetic and pharmacodynamic study of EC-cysteamine in children with cystinosis, 5 patients remained on twice-daily treatment. White blood cell cystine levels were measured 12 hours after ingestion every 4 to 8 weeks. These levels were then compared with the patient's previous 6-h post-dose levels taken while on regular cysteamine bitartrate before entering the study. Blood chemistry was also measured. RESULTS: Five children with cystinosis (mean age, 9 years; range, 8 to 17 years) who previously took cysteamine bitartrate (mean dose, 47 mg/kg body wt), received EC-cysteamine for 10 to 27 months (mean dose, 25 mg/kg body wt) and had mean white blood cell cystine levels of 0.77 and 0.71 nmol half-cystine/mg protein, respectively. During the study period, patients maintained adequate growth and there was no significant deterioration in renal or thyroid function. Two children were required to restart acid suppression after 6 months on EC-cysteamine therapy. CONCLUSIONS: Long-term, twice-daily EC-cysteamine, given at approximately 60% of the previous daily dose of cysteamine bitartrate, was effective at maintaining white blood cell cystine levels within a satisfactory range. There was no significant deterioration in renal or thyroid function.

Fertility status in male cystinosis patients treated with cysteamine.

OBJECTIVE: To analyze the fertility status in adult, male cystinosis patients treated with cysteamine. Cystinosis is an autosomal recessive disease leading to intralysosomal cystine accumulation. Worldwide, a few female cystinosis patients have given birth. However, no male cystinosis patients are known to have induced pregnancy. Adequate cysteamine treatment might improve male fertility. PATIENT(S): Seven male cystinosis patients (19-43 years) were submitted. INTERVENTION(S): Glomerular filtration rate was estimated using the Cockcroft formula. Serum LH, FSH, testosterone, and inhibin B were determined. Semen analysis was performed in five patients. Testicular biopsy was performed in one patient. RESULTS: Glomerular filtration rate ranged between 10 and 110 (normal >90) mL/min/1.73 m(2), LH and FSH levels ranged between 7.4 and 235.0 (normal 1.4-8.5) E/L and 6.8-298.0 (normal 1.5-11) E/L, respectively. Plasma testosterone level ranged between 8.7 and 31.3 (normal 11-45) nmol/L; plasma inhibin B level ranged between 10 and 210 (normal 150-400) ng/L. All of the collected sperm samples showed azoospermia. The testicular biopsy showed a Johnson score of 8 to 9. CONCLUSION(S): We demonstrate azoospermia in male cystinosis patients, even if adequately treated with cysteamine starting from an early age. The finding of spermatogenesis in the testis biopsy of one patient may provide opportunities to male cystinosis patients to produce their own offspring by in vitro fertilization after testicular sperm extraction.

Successful treatment of the murine model of cystinosis using bone marrow cell transplantation.

Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. The defective gene is CTNS encoding the lysosomal cystine transporter, cystinosin. Cystine accumulates in every organ in the body and leads to organ damage and dysfunction, including renal defects. Using the murine model for cystinosis, Ctns(-/-) mice, we performed syngeneic bone marrow cell (BMC), hematopoietic stem cell (HSC), and mesenchymal stem cell transplantation. Organ-specific cystine content was reduced by 57% to 94% in all organs tested in the BMC-treated mice. Confocal microscopy and quantitative polymerase chain reaction revealed a large quantity of transplanted BMC in all organs tested, from 5% to 19% of the total cells. Most of these cells were not from the lymphoid lineage but part of the intrinsic structure of the organ. The natural progression of renal dysfunction was prevented, and deposition of corneal cystine crystals was significantly improved in the BMC-treated mice. HSC had the same therapeutic effect as whole BMC. In contrast, mesenchymal stem cell did not integrate efficiently in any organ. This work is a proof of concept for using HSC transplantation as a therapy for cystinosis and highlights the efficiency of this strategy for a chronic, progressive degenerative disease.