Worldwide disparities in access to treatment and investigations for nephropathic cystinosis: a 2023 perspective

BACKGROUND

Nephropathic cystinosis (NC) is a rare lysosomal disease, leading to early kidney failure and extra-renal comorbidities. Its prognosis strongly relies on early diagnosis and treatment by cysteamine. Developing economies (DEing) face many challenges when treating patients for rare and chronic diseases. The aim here is to evaluate the access to investigations and treatment in DEing, and to assess for potential inequalities with Developed Economies (DEed).

METHODS

In this international cross-sectional study, a questionnaire on access, price and reimbursement of genetic, biological analyses, and treatment was sent to nephrology centers worldwide during 2022.

RESULTS

A total of 109 centers responded, coming from 49 countries and managing 741 patients: 43 centers from 30 DEing and Economies in transition (TrE), and 66 from 19 DEed. In 2022, genetics availability was 63% in DEing and 100% in DEed, whereas intra leukocytes cystine levels (IL-CL) were available for 30% of DEing patients, and 94% of DEed patients, both increasing over the last decade, as has access to immediate release cysteamine and to cysteamine eye drops in DEing. However, delayed released cysteamine can be delivered to only 7% vs. 74% of patients from DEing and DEed, respectively, and is still poorly reimbursed in DEing.

CONCLUSIONS

Over the last decade, access to investigations (namely genetics and IL-CL) and to cysteamine have improved in DEing and TrE. However, discrepancies remain with DEed: access to delayed released cysteamine is limited, and reimbursement is still profoundly insufficient, therefore limiting their current use.

Multinucleated podocytes as a clue to diagnosis of juvenile nephropathic cystinosis

BACKGROUND  : Cystinosis is a rare autosomal recessive lysosomal disorder that mainly affects the kidney and eye. Early treatment with cysteamine significantly improves the prognosis. However, early diagnosis of cystinosis, especially the juvenile nephropathic form, remains challenging because typical symptoms only become apparent in adulthood. We herein describe a 13-year-old girl who presented with proteinuria only but was diagnosed with juvenile nephropathic cystinosis based on multinucleated podocytes in her kidney biopsy specimen. We also studied the nephropathology of another case to determine the features of the multinucleated podocytes. CASE DIAGNOSIS: A previously healthy 13-year-old girl presented to our hospital because proteinuria had been detected in her school urine screening. She had been noted to have proteinuria on her school urine screening when she was 11 years of age but there was no consultation with her physician at that time. She was asymptomatic and had no other abnormalities on examination other than a relatively high urinary β-2 microglobulin level. Her kidney biopsy showed 15 multinucleated podocytes in 34 glomeruli, and the mean number of nuclei per multinucleated podocyte was 4.4. Ophthalmological examination showed cystine crystals in her cornea. Her white blood cell cystine level was high, and she was diagnosed with juvenile nephropathic cystinosis. She started oral cysteamine treatment and showed almost no progression of the disease after 2 years. In another patient with juvenile nephropathic cystinosis, there were 25 multinucleated podocytes in 63 glomeruli, and the mean number of nuclei per multinucleated podocyte was 2.9. CONCLUSION: Early diagnosis is crucial to improve the prognosis of patients with cystinosis. This report emphasizes the importance of recognizing the unique pathological feature of multinucleated podocytes as an essential clue to the diagnosis of cystinosis.

The Pitfall of White Blood Cell Cystine Measurement to Diagnose Juvenile Cystinosis

Cystinosis is an autosomal recessive lysosomal storage disease, caused by mutations in the CTNS gene, resulting in multi-organ cystine accumulation. Three forms of cystinosis are distinguished: infantile and juvenile nephropathic cystinosis affecting kidneys and other organs such as the eyes, endocrine system, muscles, and brain, and adult ocular cystinosis affecting only the eyes. Currently, elevated white blood cell (WBC) cystine content is the gold standard for the diagnosis of cystinosis. We present a patient with proteinuria at adolescent age and corneal cystine crystals, but only slightly elevated WBC cystine levels (1.31 ½ cystine/mg protein), precluding the diagnosis of nephropathic cystinosis. We demonstrate increased levels of cystine in skin fibroblasts and urine-derived kidney cells (proximal tubular epithelial cells and podocytes), that were higher than the values observed in the WBC and healthy control. CTNS gene analysis shows the presence of a homozygous missense mutation (c.590 A > G; p.Asn177Ser), previously described in the Arab population. Our observation underlines that low WBC cystine levels can be observed in patients with juvenile cystinosis, which may delay the diagnosis and timely administration of cysteamine. In such patients, the diagnosis can be confirmed by cystine measurement in slow-dividing cells and by molecular analysis of the CTNS gene.

Cystinosis: Status of research and treatment in India and the world

Cystinosis is an autosomally inherited rare genetic disorder in which cystine accumulates in the lysosome. The defect arises from a mutation in the lysosomal efflux pump, cystinosin (or CTNS). Despite the disease being known for more than a century, research, diagnosis, and treatment in India have been very minimal. In recent years, however, some research on cystinosis has been carried out on understanding the pathophysiology and in the development of a humanized yeast model for interrogating the CTNS protein. There has also been a greater awareness of the disease that has been facilitated by the formation of the Cystinosis Foundation of India just over a decade ago. Awareness among primary physicians is critical for early diagnosis, which in turn is critical for proper treatment. Eight different mutations have been observed in cystinosis patients in India, and the mutation spectrum seems different to what has been seen in the US and Europe. Despite these positive developments, there are immense hurdles still to be surmounted. This includes ensuring that the diagnosis is done sooner, making cysteamine more easily available, and, also for the future, to make accessible the promise of gene therapy to cystinosis patients.

Biomarkers in Nephropathic Cystinosis: Current and Future Perspectives

Early diagnosis and effective therapy are essential for improving the overall prognosis and quality of life of patients with nephropathic cystinosis. The severity of kidney dysfunction and the multi-organ involvement as a consequence of the increased intracellular concentration of cystine highlight the necessity of accurate monitoring of intracellular cystine to guarantee effective treatment of the disease. Cystine depletion is the only available treatment, which should begin immediately after diagnosis, and not discontinued, to significantly slow progression of renal and extra-renal organ damage. This review aims to discuss the importance of the close monitoring of intracellular cystine concentration to optimize cystine depletion therapy. In addition, the role of new biomarkers in the management of the disease, from timely diagnosis to implementing treatment during follow-up, is overviewed.

[Cystinosis : Diagnosis, cystine-depleting therapy, and transition]

This article presents a case of cystinosis in a young man. Diagnosis of the disease and the problem of transition to adult care are described. Cystinosis is a rare lysosomal storage disease with first manifestation in early childhood presenting as renal Fanconi syndrome. Without treatment, the disease leads to severe health impairment. Due to the rarity of the disease, a correct diagnosis is often delayed. Without treatment, cystinosis often leads to end-stage renal failure, blindness, hypothyroidism, diabetes mellitus, and rickets. Cystine-depleting therapy with cysteamine significantly improves mortality and quality of life.

Nephropathic Cystinosis Mimicking Bartter Syndrome: a Novel Mutation

Cystinosis is a rare autosomal recessive disorder resulting from defective lysosomal transport of cystine due to mutations in the cystinosin lysosomal cystine transporter (CTNS) gene. The clinical phenotype of nephropathic cystinosis is characterized by renal tubular Fanconi syndrome and development of end-stage renal disease during the first decade. Although metabolic acidosis is the classically prominent finding of the disease, a few cases may present with hypokalemic metabolic alkalosis mimicking Bartter syndrome. Bartter-like presentation may lead to delay in diagnosis and initiation of specific treatment for cystinosis. We report a case of a 6-year-old girl initially presenting with the features of Bartter syndrome that was diagnosed 2 years later with nephropathic cystinosis and a novel CTNS mutation.

Worldwide view of nephropathic cystinosis: results from a survey from 30 countries

BACKGROUND

Nephropathic cystinosis is a rare inherited metabolic disorder leading to progressive renal failure and extra-renal comorbidity. The prognosis relies on early adherence to cysteamine treatment and symptomatic therapies. Developing nations [DiN] experience many challenges for management of cystinosis. The aim of this study was to assess the management characteristics in DiN compared with developed nations [DeN].

METHODS

A questionnaire was sent between April 2010 and May 2011 to 87 members of the International Pediatric Nephrology Association, in 50 countries.

RESULTS

A total of 213 patients were included from 41 centres in 30 nations (109 from 17 DiN and 104 from 13 DeN). 7% of DiN patients died at a median age of 5 years whereas no death was observed in DeN. DiN patients were older at the time of diagnosis. In DiN, leukocyte cystine measurement was only available in selected cases for diagnosis but never for continuous monitoring. More patients had reached end-stage renal disease in DiN (53.2 vs. 37.9%, p = 0.03), within a shorter time of evolution (8 vs. 10 yrs., p = 0.0008). The earlier the cysteamine treatment, the better the renal outcome, since the median renal survival increased up to 16.1 [12.5-/] yrs. in patients from DeN treated before the age of 2.5 years of age (p = 0.0001). However, the renal survival was not statistically different between DeN and DiN when patients initiated cysteamine after 2.5 years of age. The number of transplantations and the time from onset of ESRD to transplantation were not different in DeN and DiN. More patients were kept under maintenance dialysis in DiN (26% vs.19%, p = 0.02); 79% of patients from DiN vs. 45% in DeN underwent peritoneal dialysis.

CONCLUSIONS

Major discrepancies between DiN and DeN in the management of nephropathic cystinosis remain a current concern for many patients living in countries with limited financial resources.

Cystinosis in adult and adolescent patients: Recommendations for the comprehensive care of cystinosis

INTRODUCTION

Cystinosis is a rare lysosomal systemic disease that mainly affects the kidney and the eye. Patients with cystinosis begin renal replacement therapy during the first decade of life in absence of treatment. Prognosis of cystinosis depends on early diagnosis, and prompt starting and good compliance with cysteamine treatment. Kidney disease progression, extra-renal complications and shorter life expectancy are more pronounced in those patients that do not follow treatment. The objective of this work was to elaborate recommendations for the comprehensive care of cystinosis and the facilitation of patient transition from paediatric to adult treatment, based on clinical experience. The goal is to reduce the impact of the disease, and to improve patient quality of life and prognosis.

METHODS

Bibliographic research and consensus meetings among a multidisciplinary professional team of experts in the clinical practice, with cystinotic patients (T-CiS.bcn group) from 5 hospitals located in Barcelona.

RESULTS

This document gathers specific recommendations for diagnosis, treatment and multidisciplinary follow-up of cystinotic patients in the following areas: nephrology, dialysis,renal transplant, ophthalmology, endocrinology, neurology, laboratory, genetic counselling,nursing and pharmacy.

CONCLUSIONS

A reference document for the comprehensive care of cystinosis represents a support tool for health professionals who take care of these patients. It is based on the following main pillars: (a) a multi-disciplinary approach, (b) appropriate disease monitoring and control of intracellular cystine levels in leukocytes, (c) the importance of adherence to treatment with cysteamine, and (d) the promotion of patient self-care by means of disease education programmes. All these recommendations will lead us, in a second phase, to create a coordinated transition model between paediatric and adult care services which will contemplate the specific needs of cystinosis.

Cystinosis: clinical presentation, pathogenesis and treatment

Nephropathic cystinosis is a rare lysosomal storage disorder caused by mutations in the CTNS gene ncoding the lysosomal cystine transporter cystinosin. Cystinosin deficiency leads to accumulation of cystine in the lysosomes of cells throughout the body and deregulation of endocytosis, trafficking of intracellular vesicles and related cell signalling processes. One of the early features of the disease is renal Fanconi syndrome characterized by polyuria, proteinuria and urinary loss of various solutes. Later in life, extrarenal complications become apparent, and decline of kidney function leads to the development of end-stage renal disease. Modern therapy of the disease is based on treatment with cystine-lowering drug cysteamine, which helps to postpone the disease progression and development of extra-renal pathologies, but offers no cure for the Fanconi syndrome. Besides the improvement of cystine-lowering therapy based on new formulations of cysteamine, further development of therapy is necessary. Some steps forward were done in the recent years, including studies of cell signalling abnormalities in cystinosis and development of stem cell and gene therapy approaches.

Long-term endocrinologic complications of cystinosis

AIM

Cystinosis is a rare autosomal recessive disorder that is characterized by defective cystine transport from lysosomes to cytoplasm and cystine crystal accumulation damaging many organs and tissues especially kidneys but extrarenal systems such as endocrine system. We aim to investigate endocrinologic complications of cystinosis

METHODS

In our study, twenty one patients were reviewed retrospectively for endocrinologic complications.

RESULTS

Eighteen (85.7%) had short stature, out of nine patients who reached pubertal age, five (55.5%) had pubertal delay, five patients (23.8%) had overt hypothyroidism and five patients (23.8%) had subclinical hypothyroidism with only elevated thyroid stimulating hormone (TSH) levels, seven (33.3%) had glucose intolerance, two (9.5%) had diabetes mellitus. Relation of these complications to age, renal functions and the dosage of cysteamine were studied.

CONCLUSION

Endocrinologic complications of cystinosis can be seen in pediatric population and it is important to understand underlying mechanisms.

[Improved prognosis of cystinosis achieved by treatment with cysteamine and by kidney transplantation]

Cystinosis is a rare, autosomal recessive disease with cystine deposits in different tissues. First signs come from kidneys and eyes, but during progression of the disease other organs can also be affected. Previously, patients with cystinosis had a very poor prognosis, but it is now considerably improved due to new methods of treatment. The purpose of this paper is to give a brief review of the disease and discuss the significant improvement of the prognosis, which has been achieved by specific medical treatment with cystine-depleting agents, and, if needed, by kidney transplantation.

Infantile nephropathic cystinosis

INTRODUCTION

Infantile nephropathic cystinosis (INC) is a metabolic disorder due to impaired carrier-mediated transport of cystine out of cellular lysosomes.

OBJECTIVE

To examine the prevalence and clinical characteristics of INC in paediatric patients with endstage renal disease (ESRD) in Serbia and give a recent statement of the disease.

METHODS

ESRD database of the Centre for Paediatric Renal Replacement Therapy (RRT) in Serbia was used to identify all patients with INC who started RRT before age of 19 years during the period January 1980 - December 2008; their records concerning clinical characteristics, therapy and outcome were evaluated.

RESULTS

Only three of 298 paediatric patients with ESRD had INC. The first signs of the illness were recognised during infancy. Fancony syndrome was diagnosed in the second year, but the diagnosis of cystinosis was delayed at mean 6 years. ESRD occurred in the first decade of life. All patients underwent cadaver kidney transplantation. At the end of the study period all patients were alive. A 31-year-old female patient was on maintenance chemodialysis due to graft failure after functioning for 11 years. She was growth retarded, single, unemployed, with severe signs of renal dystrophy. Two male patients (14.3 and 14.7 years old) had normal graft function, normal education, and good quality of life, although they were also severe growth retarded.

CONCLUSION

The prevalence of infantile nephropathic cystinosis is low in Serbia. The diagnosis of cystinosis was delayed in all patients, although they exhibited the typical course of the disease.

Non-invasive measurements of atherosclerosis in adult cystinosis patients

BACKGROUND

Cystinosis is characterized by intralysosomal cystine accumulation, causing end stage renal disease around 10 years of age if not treated with cysteamine. Cystine accumulation in blood vessels might increase atheroma formation or arterial stiffness and therefore increase the risk for cardiovascular disease (CVD). This study aimed to investigate the risk for CVD by non-invasive measures of atherosclerosis (NIMA) and to evaluate the effect of cysteamine treatment.

PATIENTS AND METHODS

Thirteen Dutch adult cystinosis patients were included. White blood cell (WBC) cystine levels, glomerular filtration rate (GFR) and concommitant medications were obtained from medical records. NIMA included carotid intima-media thickness (cIMT, n = 13), pulse wave velocity (PWV, n = 8) and pulse wave analysis (PWA, n = 6).

RESULTS

GFR ranged between 4-95 mL/min/1.73 m². All but one patient were treated with cysteamine, mean WBC cystine values ranged between 0.34-1.64 nmol cystine/mg protein, 8 patients had mean WBC cystine levels <1 nmol cystine/mg protein. When compared to healthy subjects, cIMT and PWV levels were above normal values in 1 patient for each measure. PWA measurements showed high augmentation index in three patients who did not receive lipid-lowering medication. When corrected for renal function, cIMT and PWV levels were within the normal range.

CONCLUSION

Young adult cystinosis patients treated with cysteamine have no additional risk for CVD when compared to patients with chronic kidney disease of other causes.

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.

Chitotriosidase plasma activity in nephropathic cystinosis

Chitotriosidase is a fully active chitinase produced and secreted by activated phagocytes. Plasma chitotriosidase activity is a well-established marker of total disease burden in Gaucher disease that has proved useful in monitoring the response to both enzyme replacement and substrate reduction therapies in patients with Gaucher disease. Increased chitotriosidase plasma activity has also been observed in several other lysosomal and non lysosomal disorders. Cystinosis, a rare multisystemic lysosomal storage disease, is characterized by the intralysosomal accumulation of free cystine in many cell types including phagocytes. We here report on plasma chitotriosidase activity in a child with nephropathic cystinosis. Increased plasma chitotriosidase activity (481 nmol/h per ml; normal range 0-150 units) was found on diagnosis and prior to the initiation of oral cysteamine (Cystagon) treatment. Serial estimations of plasma chitotriosidase activity showed that it correlated with leukocyte cystine content and decreased to 100 nmol/h per ml following 14 months' treatment. This novel observation suggests that cystinosis should be included in the differential diagnosis of disorders associated with increased plasma chitotriosidase activity. Furthermore, it suggests that serial estimations of plasma chitotriosidase activity could be of value in monitoring the response to oral cysteamine treatment in cystinosis.

Gastrointestinal manifestations of nephropathic cystinosis in children

INTRODUCTION

Cystinosis is an autosomal recessive disorder which is characterized by both renal and extrarenal symptoms. Gastrointestinal dysfunction has been reported in adolescent with cystinosis, and it is rarely considered in the infants. The present case series reviewed gastrointestinal manifestations of these patients.

MATERIALS AND METHODS

Gastrointestinal signs and symptoms of 23 children aged 5.99 +/- 0.50 years (range, 1.0 to 12.5 years) on average with cystinosis, admitted to our department of nephrology between 1996 and 2005, were retrospectively reviewed. The inclusion criteria were the presence of the crystals of cystine in bone marrow aspiration and corneal deposition detected by slit lamp examination.

RESULTS

Gastrointestinal signs and symptoms were as follows: vomiting in 16 patients (69.6%), hepatomegaly in 8 (34.8%), diarrhea in 6 (26.1%), splenomegaly in 5 (21.7%), constipation in 4 (17.4%), anorexia in 4 (17.4%), abdominal pain in 3 (13.0%), nausea in 2 (8.7%), and ascites in 2 (8.7%). Height below the 3rd percentile in was seen in 16 patients (69.6%) and weight below the 3rd percentile, in 17 (73.9%). Fifteen patients (65.2%) had both low weight and low height. Esophagogastroduodenoscopy had been performed in 6 cases and chronic inactive gastritis with H pylori infection was detected in 2 patients (8.7%).

CONCLUSIONS

Our study revealed a wide spectrum of gastrointestinal disturbances in young patients with cystinosis. Such findings should lead to greater awareness of the presence of gastrointestinal dysfunction in these children, encourage prompt gastrointestinal evaluation, and encourage treatment of more severely affected patients.

Nephropathic cystinosis in children: An overlooked disease

Nephropathic cystinosis is rare genetic disease characterized by defective lysosomal cystine transport and increased lysosomal cystine. Corneal Cystine Crystal Scoring (CCCS) for diagnosis of nephropathic cystinosis was studied in all suspected children with renal Fanconi syndrome and siblings of diagnosed cases over a two year period. In addition to oral cysteamine, cysteamine eye drops were provided to all diagnosed patients and CCCS was followed up on a quarterly basis. Of 33 screened cases, 14 had corneal cystine crystals. Crystals were absent in two cystinotic patients under the age of 20 months. The mean age at diagnosis was 52.7 months and five patients had ERSD. After six months of treatment, the mean CCCS did not increase from the initial value of 1.81; associated with a decrease of 0.5 in two cases and a similar increase in two others. Scores decreased in two other patients after 12 months. Compliance was generally inadequate due to the high frequency of administration and the need for multi-drug regimen. CCCS is a simple and reasonably sensitive method for diagnosis of nephropathic cystinosis above two years of age. Topical treatment with cysteamine eye drops prevents progression of deposits and may decrease it with adequate compliance. Further follow up is still recommended to monitor long term effects of both systemic and topical cysteamine therapy.

Specific cognitive deficits in young children with cystinosis: evidence for an early effect of the cystinosin gene on neural function

OBJECTIVES

Infantile nephropathic cystinosis is associated with a specific cognitive deficit in visual spatial processing in older children and adults. The cause of this deficit is unknown. This study was designed to determine whether the cognitive deficit is present in young children with cystinosis, suggesting an early effect of the genetic disorder on brain development.

STUDY DESIGN

Young children (n = 25; age, 3-8 years) with cystinosis and 25 matched control subjects underwent cognitive testing, including tests of intelligence, visual perceptual, visual spatial, and visual motor functions.

RESULTS

Children with cystinosis performed significantly more poorly on tests of visual spatial and visual motor function than did control subjects. Visual perceptual abilities were equivalent in the 2 groups.

CONCLUSION

The same pattern of visual spatial deficit is present in young children with cystinosis as has previously been demonstrated in older children and adults, which suggests that there may be an influence of the cystinosis gene on brain development, rather than an adverse effect of prolonged cystine accumulation in the brain during childhood.

In vivo confocal microscopy and polarizing microscopy of the cornea in a patient with nephropathic cystinosis

The clinicopathological and in vivo confocal microscopic characteristics of the corneas from a patient with infantile cystinosis is reported. Crystals were demonstrated in the epithelium and stroma of this patient.

Measurement of cystine in granulocytes using liquid chromatography-tandem mass spectrometry

BACKGROUND

Cystinosis is a rare autosomal recessive disorder characterized by an accumulation of intralysosomal cystine due to a defect in cystine transport across the lysosomal membrane. This disorder can be treated specifically using high doses of cysteamine. Accurate measurement of intracellular cystine content is necessary for the diagnosis and monitoring of treatment with cysteamine. Here we describe a new method to measure intracellular cystine. It relies on a liquid chromatography-tandem mass spectrometry assay. We compare this novel method with the cystine-binding protein assay.

METHOD

Cells were isolated and lysed in the presence of N-ethylmaleimide to avoid interference from cysteine. After deproteinization, addition of stable isotope d6 cystine and butylation, cystine was measured using an API 3000 MSMS.

RESULTS

The cystine assay was linear to at least 50 micromol/L. Within-run and between-run coefficients of variation were 2.9% and 5.7% respectively.

CONCLUSION

It is possible to measure very low concentrations of intracellular cystine with liquid chromatography-tandem mass spectrometry. The results obtained with this novel method correlate very well with those obtained using the cystine-binding protein assay.

Nodular regenerative hyperplasia and severe portal hypertension in cystinosis

BACKGROUND & AIMS

Cystinosis is a rare autosomal-recessive disorder characterized by the intralysosomal accumulation of cystine, which is responsible for widespread tissue destruction. Liver biopsy specimens of patients with cystinosis show cystine crystal formation in Kupffer cells. However, significant liver disease and portal hypertension is not a common complication of cystinosis. We report the case histories of 2 young men with poorly treated nephropathic cystinosis who developed noncirrhotic portal hypertension with evidence of nodular regenerative hyperplasia (NRH).

METHODS

Liver biopsy examinations, upper and lower endoscopy with biopsy examination, imaging studies, venous pressure measurements, and laboratory investigations were used to evaluate the causes of the liver disease and portal hypertension.

RESULTS

Histologic examination of liver biopsy specimens from both patients showed changes characteristic of NRH with portal hypertension documented by measurement of pressure gradients. In addition, endoscopy in the first patient showed varices and portal hypertensive gastropathy.

CONCLUSIONS

NRH was confirmed by histologic examination of the liver in both patients and is the likely cause of their portal hypertension. NRH may represent a rare, late complication of cystinosis, although the mechanism remains undefined.

Prenatal diagnosis of cystinosis by quantitative measurement of cystine in chorionic villi and cultured cells

OBJECTIVE

Prenatal diagnosis of cystinosis has been available for over 30 years by the incubation of cultured amniotic cells, intact chorionic villi and cultured chorionic cells with [35S]-cystine followed by thin layer chromatography and visual inspection of autoradiographs of the chromatograms for cystine. This method has proved highly reliable but because of the short half-life of [35S]-cystine, its cost and the length of the assay procedure, an alternative method of diagnosis was investigated.

METHOD

Cystine was quantitatively measured in chorionic villi directly, in cultured chorionic villi and cultured amniotic cells using a cystine-binding protein from Escherichia coli.

RESULTS

Twelve pregnancies at risk for cystinosis were monitored by both the [35S]-cystine uptake method and the new quantitative method in uncultured chorionic villi. There was no discrepancy between the results obtained with the two methods and subsequently 15 pregnancies have been monitored by the quantitative assay only--13 in chorionic villi directly, 1 in cultured chorionic villi cells and 1 in cultured amniotic cells. Grossly elevated levels of cystine were found in seven pregnancies.

CONCLUSION

An unequivocal diagnosis of cystinosis can be made within 24 h of sampling by the quantitative measurement of cystine in uncultured chorionic villi.

[Cystinosis: an infrequent cause of distal myopathy]

INTRODUCTION

Cystinosis is a hereditary disease with clinical symptoms that are caused by the accumulation of cystine crystals in different tissues. Distal vacuolar myopathy has been reported as one of its later complications.

CASE REPORT

Here, we present the case of a 20-year-old male diagnosed with cystinosis at the age of 2 years, with severe renal involvement that required a transplant. The patient gradually developed weakness and atrophy of the muscles in his hands. Neurophysiological and histological studies enabled a diagnosis of distal vacuolar myopathy to be established, and electron microscopy revealed deposits of cystine crystals.

CONCLUSIONS

Cystinosis must be included within the differential diagnosis of distal myopathies. Timely treatment with cysteamine could prevent the development of this complication.

[Cystinosis: diagnosis through the measurement of the leukocyte cystine content by HPLC]

BACKGROUND AND OBJECTIVE

Cystinosis is an autosomal recessive disorder characterized by an accumulation of intralysosomal cystine. Three disease forms exist, infantile, juvenile or late-onset, and ocular nonnephropathic cystinosis, delineated on the basis of severity of symptoms and age of onset. The knowledge of early clinic manifestations and the onset of the appropriate therapy delay the evolution of the disease and improve the general conditions. Therefore, it is necessary to develop a sensible diagnostic method for early detection and treatment of the disease. CLINICAL CASE AND METHODS: The leukocyte cystine content was determined by HPLC in a 42 years old female patient after renal transplantation, and with the clinical characteristic complications of the intermediate cystinosis. Equally, the molecular characterization of the structural defects of the cystinosin (CTNS) gene was made in the patient and in all family members.

RESULTS

By measuring of the leukocyte cystine content in the patient and family members, we have determined 5 family members as heterozygous. This result was confirmed by molecular analysis that showed the approximately 65 kb deletion in the 5 family members. The patient was heterozygous for the approximately 65 kb deletion, and the second alteration was not determined.

CONCLUSIONS

We presented a useful diagnostic method, based in the determination of cystine content of polymorphonuclear leukocytes, which permits to detect the heterozygous individuals.

Keratopathy of multiple myeloma masquerading as corneal crystals of ocular cystinosis

We describe a 49-year-old woman in whom ocular cystinosis was diagnosed on the basis of a routine eye examination 12 years previously. Conjunctival biopsy was reported to support the diagnosis. The patient described photophobia for the past 5 years and reported a 2-fold increase in her serum IgG level for the past 12 years. On ophthalmic examination, corneal crystals were evident in the epithelium and superficial stromal layers, rather than throughout the corneal epithelium and the entire stroma as in ocular cystinosis. The patient's serum protein level was elevated at 8.7 g/dL; protein electrophoresis showed an elevated gamma-globulin peak, and the IgG level was twice that of normal at 2820 mg/dL. Bone marrow biopsy confirmed the diagnosis of multiple myeloma. This case illustrates that multiple myeloma can mimic corneal findings of cystinosis.

Early oral cysteamine therapy for nephropathic cystinosis

Nephropathic cystinosis is an autosomal recessive lysosomal storage disorder in which intracellular cystine accumulates due to impaired transport out of lysosomes. The clinical manifestations include renal tubular Fanconi syndrome in the 1st year of life, with hypophosphatemic rickets, hypokalemia, polyuria, dehydration and acidosis, growth retardation, hypothyroidism, photophobia, renal glomerular deterioration by 10 years of age, and late complications such as myopathy, pancreatic insufficiency, and retinal blindnesss. The cystinosis gene, CTNS, codes for cystinosin, a 367 amino acid protein with seven transmembrane domains. More than 50 CTNSmutations have been identified, but approximately 50% of Northern European patients have a 57257-bp deletion which removes the first nine exons of CTNS. The mainstay of cystinosis therapy is oral cysteamine (Cystagon). This aminothiol can lower intracellular cystine content by 95%, and has proven efficacy in delaying renal glomerular deterioration, enhancing growth, preventing hypothyroidism, and lowering muscle cystine content. Its early and diligent use is critical; in one study, for every month of treatment prior to 3 years of age, 14 months' worth of later renal function were preserved. Several examples of individual patients treated early and having preserved renal function and normal growth are available. Newborn screening using a chip containing cDNA to detect common CTNSmutations may allow diagnosis and treatment in the first weeks of life.

CONCLUSIONS

Early diagnosis and treatment of nephropathic cystinosis can change the course of this disease.