Swallowing dysfunction in nephropathic cystinosis

Gastrointestinal challenges in nephropathic cystinosis: clinical perspectives

Gastrointestinal (GI) sequelae, such as vomiting, hyperacidity, dysphagia, dysmotility, and diarrhea, are nearly universal among patients with nephropathic cystinosis. These complications result from disease processes (e.g., kidney disease, cystine crystal accumulation in the GI tract) and side effects of treatments (e.g., cysteamine, immunosuppressive therapy). GI involvement can negatively impact patient well-being and jeopardize disease outcomes by compromising drug absorption and patient adherence to the strict treatment regimen required to manage cystinosis. Given improved life expectancy due to advances in kidney transplantation and the transformative impact of cystine-depleting therapy, nephrologists are increasingly focused on addressing extra-renal complications and quality of life in patients with cystinosis. However, there is a lack of clinical data and guidance to inform GI-related monitoring, interventions, and referrals by nephrologists. Various publications have examined the prevalence and pathophysiology of selected GI complications in cystinosis, but none have summarized the full picture or provided guidance based on the literature and expert experience. We aim to comprehensively review GI sequelae associated with cystinosis and its treatments and to discuss approaches for monitoring and managing these complications, including the involvement of gastroenterology and other disciplines.

Multidisciplinary and multidimensional approaches to transplantation in children with rare genetic kidney diseases

In this review, we describe the multidisciplinary, multidimensional care required to optimize outcomes for pediatric transplant recipients with rare genetic kidney diseases. Transplant success, recipient survival, and improvement in quality of life depend on collaboration between patients, families, and a team of specialists with medical, as well as nonmedical expertise. A multidisciplinary transplant team composed of experts from medicine, surgery, nursing, nutrition, social services, transplant coordination, psychology, and pharmacology, is now standard in most transplant centers and is critical to the success of a transplant. In addition to these professionals, other specialists, such as cardiologists, urologists, geneticists, metabolic disease specialists, occupational therapists, case management, child life, chaplain, and palliative care services, have a crucial role to play in the preparation, surgery, and follow-up care, especially when a pediatric patient has a rare genetic disorder leading to renal involvement, and the need for transplantation. In order to describe this multidisciplinary care, we divide the genetic renal diseases into five subgroups-metabolic and tubular disorders, glomerular diseases, congenital anomalies of the kidney and urinary tract, ciliopathies including cystic diseases, and miscellaneous renal conditions; and describe for each, the need for care beyond that provided by the standard transplant team members.

Health-related quality of life and patient-reported outcome measurements in patients with cystinosis

Nephropathic cystinosis is a rare autosomal recessive lysosomal storage disorder. With the availability of treatment and renal replacement therapy, nephropathic cystinosis has evolved from an early fatal disease to a chronic, progressive disorder with potentially high impairment. We aim to review the literature on the health-related quality of life and identify appropriate patient-reported outcome measurements to assess the health-related quality of life of patients with cystinosis. For this review, we conducted a literature search in PubMed and Web of Science in September 2021. Inclusion and exclusion criteria for the selection of articles were defined a priori. We identified 668 unique articles through the search and screened them based on title and abstract. The full texts of 27 articles were assessed. Finally, we included five articles (published between 2009 and 2020) describing the health-related quality of life in patients with cystinosis. All studies, apart from one, were conducted in the United States, and no condition-specific measurement was used. Patients with cystinosis reported a lower health-related quality of life (for certain dimensions) than healthy subjects. Few published studies address the health-related quality of life of patients with cystinosis. Such data must be collected standardized and follow the FAIR (Findable, Accessible, Interoperable, and Reusable) principles. To gain a comprehensive understanding of the impact of this disorder on health-related quality of life, it is necessary to use generic and condition-specific instruments to measure this, preferably in large samples from longitudinal studies. A cystinosis-specific instrument for measuring health-related quality of life has yet to be developed.

Relationship between age at initiation of cysteamine treatment, adherence with therapy, and glomerular kidney function in infantile nephropathic cystinosis

Infantile nephropathic cystinosis, due to impaired transport of cystine out of lysosomes, occurs with an incidence of 1 in 100-200,000 live births. It is characterized by renal Fanconi syndrome in the first year of life and glomerular dysfunction progression to end-stage kidney disease by approximately 10 years of age. Treatment with oral cysteamine therapy helps preserve glomerular function, but affected individuals eventually require kidney replacement therapy. This is because glomerular damage had already occurred by the time a child is diagnosed with cystinosis, typically in the second year of life. We performed a retrospective multicenter study to investigate the impact of initiating cysteamine treatment within the first 2 months of life in some infants and comparing two different levels of adherence in patients diagnosed at the typical age. We collected 3983 data points from 55 patients born between 1997 and 2020; 52 patients with 1592 data points could be further evaluated. These data were first analyzed by dividing the patient cohort into three groups: (i) standard treatment start with good adherence, (ii) standard treatment start with less good adherence, and (iii) early treatment start. At every age, mean estimated glomerular filtration rate (eGFR) was higher in early-treated patients than in later-treated patients. Second, a generalized additive mixed model (GAMM) was applied showing that patients with initiation of treatment before 2 months of age are expected to have a 34 ml/min/1.73 m² higher eGFR than patients with later treatment start while controlling for adherence and patients' age. These data strongly suggest that oral cysteamine treatment initiated within 2 months of birth preserves kidney function in infantile nephropathic cystinosis and provide evidence of the utility of newborn screening for this disease.

Longitudinal dysphagia assessment in adult patients with nephropathic cystinosis using the Modified Barium Swallow Impairment Profile

INTRODUCTION/AIMS

Nephropathic cystinosis is a lysosomal storage disorder with known myopathic features, including dysphagia. Evaluation of oropharyngeal swallowing physiology can be standardized using the Modified Barium Swallow Impairment Profile (MBSImP), a validated assessment tool used to analyze and rate swallowing across 17 distinct physiologic domains. Our objective was to better characterize swallowing impairments in nephropathic cystinosis using MBSImP analysis.

METHODS

We retrospectively evaluated 40 video fluoroscopic swallowing studies performed at two time points over 1 y in patients with nephropathic cystinosis with various levels of oral and pharyngeal stage dysphagia. Patients completed two self-administered dysphagia outcome measures (the M. D. Anderson Dysphagia Inventory [MDADI] and the 10-item Eating Assessment Tool [EAT-10]).

RESULTS

We demonstrated oral stage and pharyngeal stage dysphagia across domains that impacted bolus control, transit, and clearance through both the oral cavity and pharyngeal lumen. Also captured were deficits related to onset and completeness of laryngeal closure that impact airway protection during swallow. There were significant correlations between pharyngeal total score and EAT-10 (r = 0.5, p < 0.001) and between oral total score and EAT-10 (r = 0.7, p < 0.001), MDADI-e (r = -0.6, p < 0.001), MDADI-p (r = -0.5, p < 0.001) and MDADI-c (r = -0.6, p < 0.001). There were no differences in oral or pharyngeal total scores across the 1-y time span.

DISCUSSION

This study identifies oral and pharyngeal stage dysphagia as crucial to patients with nephropathic cystinosis and paves the path for future studies of treatment targets.

Adult complications of nephropathic cystinosis: a systematic review

While nephropathic cystinosis is classically thought of as a childhood disease, with improved treatments, patients are more commonly living into adulthood. We performed a systematic review of the literature available on what complications this population faces as it ages. Nearly every organ system is affected in cystinosis, either from the disease itself or from sequelae of kidney transplantation. While cysteamine is known to delay the onset of end-stage kidney disease, its effects on other complications of cystinosis are less well determined. More common adult-onset complications include myopathy, diabetes, and hypothyroidism. Some less common complications, such as neurologic dysfunction, can still have a profound impact on those with cystinosis. Areas for further research in this area include additional study of the impact of cysteamine on the nonrenal manifestations of cystinosis, as well as possible avenues for new and novel treatments.

Clinical trial readiness study of distal myopathy and dysphagia in nephropathic cystinosis

BACKGROUND

Nephropathic cystinosis is a lysosomal storage disorder with late-onset systemic complications, such as myopathy and dysphagia. Currently employed outcome measures lack sensitivity and responsiveness for dysphagia and myopathy, a limitation to clinical trial readiness.

METHODS

We evaluated 20 patients with nephropathic cystinosis in two visits over the course of a year to identify outcomes sensitive to detect changes over time. Patients also underwent an expiratory muscle strength training program to assess any effects on aspiration and dysphagia.

RESULTS

There were significant differences in the Timed Up and Go Test (TUG) and Timed 25-Foot Walk (25-FW) between baseline and 1-y follow-up (P < .05). Maximum expiratory pressure (MEP) and peak cough flow (PCF) significantly improved following respiratory training (P < .05).

CONCLUSIONS

Improved respiratory outcomes may enhance patients ability to expel aspirated material from the airway, stave off pulmonary sequelae associated with chronic aspiration, and yield an overall improvement in physical health and well-being.

Clinical myopathy in patients with nephropathic cystinosis

BACKGROUND

Nephropathic cystinosis is a lysosomal storage disorder. Patient survival years after renal transplantation has revealed systemic complications including distal myopathy and dysphagia.

METHODS

We evaluated 20 adult patients with nephropathic cystinosis using patient-reported and clinical outcome measures. Standard motor measures, video fluoroscopy swallow studies, and tests of respiratory function were performed. We also used Rasch analysis of an initial survey to design a 16-item survey focused on upper and lower extremity function, which was completed by 31 additional patients.

RESULTS

Distal myopathy and dysphagia were common in patients with nephropathic cystinosis. Muscle weakness ranges from mild involvement of intrinsic hand muscles to prominent distal greater than proximal weakness and contractures.

CONCLUSIONS

In addition to further characterization of underlying dysphagia and muscle weakness, we propose a new psychometrically devised, disease specific, functional outcome measures for distal myopathy in patients with nephropathic cystinosis.

Vigier R, Zustin J, Haffner D. Management of bone disease in cystinosis: Statement from an international conference

Cystinosis is an autosomal recessive storage disease due to impaired transport of cystine out of lysosomes. Since the accumulation of intracellular cystine affects all organs and tissues, the management of cystinosis requires a specialized multidisciplinary team consisting of pediatricians, nephrologists, nutritionists, ophthalmologists, endocrinologists, neurologists' geneticists, and orthopedic surgeons. Treatment with cysteamine can delay or prevent most clinical manifestations of cystinosis, except the renal Fanconi syndrome. Virtually all individuals with classical, nephropathic cystinosis suffer from cystinosis metabolic bone disease (CMBD), related to the renal Fanconi syndrome in infancy and progressive chronic kidney disease (CKD) later in life. Manifestations of CMBD include hypophosphatemic rickets in infancy, and renal osteodystrophy associated with CKD resulting in bone deformities, osteomalacia, osteoporosis, fractures, and short stature. Assessment of CMBD involves monitoring growth, leg deformities, blood levels of phosphate, electrolytes, bicarbonate, calcium, and alkaline phosphatase, periodically obtaining bone radiographs, determining levels of critical hormones and vitamins, such as thyroid hormone, parathyroid hormone, 25(OH) vitamin D, and testosterone in males, and surveillance for nonrenal complications of cystinosis such as myopathy. Treatment includes replacement of urinary losses, cystine depletion with oral cysteamine, vitamin D, hormone replacement, physical therapy, and corrective orthopedic surgery. The recommendations in this article came from an expert meeting on CMBD that took place in Salzburg, Austria, in December 2016.

Swallowing dysfunction in patients with nephropathic cystinosis

INTRODUCTION

Nephropathic cystinosis is a rare autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene. Patients with nephropathic cystinosis suffer not only from renal disease but have also other systemic complications like myopathy and swallowing dysfunction. Dysphagia for solid food is mentioned in patients with cystinosis, but in clinical practice swallowing investigations are only performed when the patient has complaints. The aim of this study was to explore the swallowing function in patients with cystinosis by use of the Test of Mastication and Swallowing Solids (TOMASS), and to compare their performance with patients with myotonic dystrophy type 1 - a neuromuscular disease in which dysphagia for solid food is a known problem.

METHODS

Twenty adult patients with cystinosis (11 men and 9 women, range 19-51 years) and 10 patients with myotonic dystrophy type 1 (5 men and 5 women, range 20-60 years) were included. All cystinosis patients were treated with cysteamine. Data of the two groups were compared with normative data using independent-samples t-tests. In case the variables were not normally distributed, the non-parametric Mann-Whitney U test was used.

RESULTS

There was a significant difference in the number of bites, masticatory cycles, swallows and total time between the normal values and cystinosis patients. The results of the cystinosis patients were comparable to those of the patients with myotonic dystrophy.

DISCUSSION AND CONCLUSION

Adult patients with cystinosis have significant dysphagia for solid food. Clinicians treating these patients should be aware of this fact. The TOMASS can be performed easily in clinical practice to investigate whether patients with cystinosis have swallowing dysfunction. The swallowing dysfunction can now be diagnosed by use of a non-invasive, very simple, non-harmful test. It can be discussed whether this should be added to the regular care scheme of cystinosis patients in order to regularly follow-up swallowing function.

A systematic literature review of cysteamine bitartrate in the treatment of nephropathic cystinosis

OBJECTIVES

To summarize available clinical evidence for cysteamine bitartrate preparations in the treatment of nephropathic cystinosis as identified through a systematic literature review (SLR).

METHODS

We searched MEDLINE, MEDLINE In-Process and Embase using Ovid with a predefined search strategy through 19 January 2016. All publicly available clinical reports on the use of delayed-release (DR) cysteamine bitartrate (Procysbi ¹ ) or immediate-release (IR) cysteamine bitartrate (Cystagon ² ) in patients with cystinosis were included.

RESULTS

We identified a total of 103 publications and 10 trial records. Of these, 9 studies describe DR cysteamine bitartrate (n = 267 patients), 42 describe IR cysteamine bitartrate (n = 1,427 patients) and in 53 studies the exact preparation was not specified (n = 906 patients). The vast majority of the studies used a non-randomized study design, with randomized clinical trials (RCTs) being scarce (1 study comparing DR and IR formulation) and case reports (n = 49) being the most common study design representing 47% of the total.

CONCLUSION

A substantial evidence base for cysteamine bitartrate in the treatment of nephropathic cystinosis was identified. However, the majority of the evidence was of relatively low quality, with evidence levels of 3 or 4.

Nephropathic cystinosis: an update

PURPOSE OF REVIEW

Over the past few decades, cystinosis, a rare lysosomal storage disorder, has evolved into a treatable metabolic disease. The increasing understanding of its pathophysiology has made cystinosis a prototype disease, delivering new insights into several fundamental biochemical and cellular processes.

RECENT FINDINGS

In this review, we aim to provide an overview of the latest advances in the pathogenetic, clinical, and therapeutic aspects of cystinosis.

SUMMARY

The development of alternative therapeutic monitoring strategies and new systemic and ocular cysteamine formulations might improve outcome of cystinosis patients in the near future. With the dawn of stem cell based therapy and new emerging gene-editing technologies, novel tools have become available in the search for a cure for cystinosis.

Chiari I Malformation in Nephropathic Cystinosis

OBJECTIVE

To determine the relative incidence of Chiari I malformations in children with cystinosis compared with those in the general population.

STUDY DESIGN

Magnetic resonance imaging scans were performed on 53 patients with nephropathic cystinosis and 120 controls, age range 3-18 years.

RESULTS

Ten of 53 (18.9%) patients with cystinosis had Chiari I or tonsillar ectopia, and only 2 of 120 controls (1.6%) had a similar finding. At least 2 of the patients had symptoms or signs thought to be related to the malformation, and one had surgical decompression. Two had an associated cervical syrinx.

CONCLUSIONS

Children with cystinosis have a 12-fold higher prevalence of Chiari I malformations than the general pediatric population. Chiari I malformations should be high on the differential diagnosis when individuals with cystinosis develop neurologic signs and symptoms, and magnetic resonance imaging scans should be performed on children with cystinosis who present with new-onset headache, ataxia, incontinence, or other unexplained neurologic symptoms.

Cystinosis as a lysosomal storage disease with multiple mutant alleles: Phenotypic-genotypic correlations

Cystinosis is an autosomal recessive lysosomal storage disease with an unclear enzymatic defect causing lysosomal cystine accumulation with no corresponding elevation of plasma cystine levels leading to multisystemic dysfunction. The systemic manifestations include a proximal renal tubular defect (Fanconi-like), endocrinal disturbances, eye involvements, with corneal, conjunctival and retinal depositions, and neurological manifestations in the form of brain and muscle dysfunction. Most of the long-term ill effects of cystinosis are observed particularly in patients with long survival as a result of a renal transplant. Its responsible CTNS gene that encodes the lysosomal cystine carrier protein (cystinosin) has been mapped on the short arm of chromosome 17 (Ch17 p13). There are three clinical forms based on the onset of main symptoms: nephropathic infantile form, nephropathic juvenile form and non-nephropathic adult form with predominant ocular manifestations. Avoidance of eye damage from sun exposure, use of cystine chelators (cysteamine) and finally renal transplantation are the main treatment lines. Pre-implantation genetic diagnosis for carrier parents is pivotal in the prevention of recurrence.

Cystinosis, Fanconi syndrome, and odontogenic cysts

Cystinosis is a multisystemic genetic storage disorder characterized by a mutation in the transporter system of cystine. The disease particularly affects the renal system by causing deposition of cystine crystals leading to, if untreated, Fanconi syndrome and end-stage renal disease. This disease also affects the ocular system, central nervous system, endocrine system, hepatobiliary system, and musculoskeletal system. We present the first case of cystine crystal deposition within an odontogenic cyst, confirmed by the correlation of the clinical, radiographic, and histologic findings on this patient.

Long-term tracking of neurological complications of encephalopathy and myopathy in a patient with nephropathic cystinosis: a case report and review of the literature

Introduction

Cystinosis is a hereditary storage disease resulting in intracellular accumulation of cystine and crystal formation that causes deterioration of the function of many organs. The major clinical symptom is renal failure, which progresses and necessitates renal transplantation at the beginning of the second decade of life. Encephalopathy and distal myopathy are important neurological long-term complications with a major impact on the quality of life of these patients. Application of cysteamine is the only specific therapy available; it decreases the intracellular cystine level and delays or may even prevent the failure of organ functions.

Case presentation

We present the case of a 38-year-old woman with cystinosis and the long-term tracking of her neurological symptoms under cysteamine treatment.

Conclusion

This case report describes a long observation period of neurological complications in a person with cystinosis who had strikingly different courses of encephalopathy and myopathy while on cysteamine treatment. Although encephalopathy was initially suspected, this did not develop, but distal myopathy progressed continuously despite specific therapy.

Nephropathic cystinosis: late complications of a multisystemic disease

Cystinosis is a rare autosomal recessive disorder due to impaired transport of cystine out of cellular lysosomes. Its estimated incidence is 1 in 100,000 live births. End-stage renal disease (ESRD) is the most prominent feature of cystinosis and, along with dehydration and electrolyte imbalance due to renal tubular Fanconi syndrome, has accounted for the bulk of deaths from this disorder. Prior to renal transplantation and cystine-depleting therapy with cysteamine for children with nephropathic cystinosis, their lifespan was approximately 10 years. Now, cystinotic patients have survived through their fifth decade, but the unremitting accumulation of cystine has created significant non-renal morbidity and mortality. In this article we review the classic presentation of nephropathic cystinosis and the natural history, diagnosis, and treatment of the disorder's systemic involvement. We also emphasize the role of oral cysteamine therapy in preventing the late complications of cystinosis.

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.

Coronary artery and other vascular calcifications in patients with cystinosis after kidney transplantation

Cystinosis, an autosomal recessive disorder of lysosomal cystine accumulation, results from mutations in the CTNS gene that encodes the lysosomal cystine transporter, cystinosin. Renal tubular Fanconi syndrome occurs in infancy, followed by rickets, growth retardation, photophobia, and renal failure, which requires renal transplantation at approximately 10 yr of age. Treatment with cysteamine decreases cellular cystine levels, retards renal deterioration, and allows for normal growth. Patients with a history of inadequate cystine depletion therapy may survive, after renal transplantation, into the third to fifth decades but will experience other, extrarenal complications of the disease. Routine chest and head computed tomography scans of 41 posttransplantation patients with cystinosis were reviewed for vascular calcification. The radiologic procedures had been performed to examine lung and brain parenchyma, so there was little ascertainment bias. Thirteen of the 41 patients had vascular calcification, including 11 with coronary artery calcification. One 25-yr-old man required three-vessel coronary artery bypass graft surgery. There were no significant differences between the 13 patients with calcification and the 28 without calcification in the following parameters: Time on dialysis, frequency of transplantation, hypertension, hypercholesterolemia, homozygosity for the 57-kb deletion in CTNS, serum creatinine, and calcium-phosphate product. However, the finding of vascular calcification correlated directly with duration of life without cysteamine therapy and inversely with duration of life under good cystine-depleting therapy. The accumulation of intracellular cystine itself maybe a risk factor for vascular calcifications, and older patients with cystinosis should be screened for this complication.

Quantitative lingual, pharyngeal and laryngeal ultrasonography in swallowing research: a technical review

Because of its distinct advantage in radiation-free soft tissue imaging, ultrasonography has been widely used to study lingual, pharyngeal, hyoid, laryngeal, and even esophageal action during swallowing in individuals of all ages. Qualitative ultrasonographic observations have made considerable contributions to our understanding of deglutition. Quantitative ultrasonographic swallowing research has also grown by leaps and bounds over the years with advances in imaging technologies and analytical methodologies. As a technical primer for new investigators, this paper reviews the modem methods for quantitative analysis in ultrasonographic swallowing research. The intended outcome is a basic understanding of the application of ultrasonography with various analysis options to the quantitative study of the deglutitive action of selected upper aerodigestive structures. Though proven useful for swallowing research, ultrasonography has inherent limitations and methodological issues. Future technological advancement and sophisticated image processing and analysis algorithms will resolve some of these issues.

Swallowing dysfunction in 101 patients with nephropathic cystinosis: benefit of long-term cysteamine therapy

Nephropathic cystinosis is a rare, autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene that codes for a cystine transporter in the lysosomal membrane. Affected patients store 50-100 times the normal amounts of cystine in their cells, and suffer renal tubular and glomerular disease, growth retardation, photophobia, and other systemic complications, including a myopathy and swallowing dysfunction. Using videofluoroscopy and ultrasound examinations, we assessed the swallowing function of 101 patients with nephropathic cystinosis on their most recent admission to the National Institutes of Health Clinical Center between 1987 and 2004. These patients ranged in age from 6 to 45 years; more than half had significant complaints of swallowing difficulty. On examination of barium swallow, the oral, pharyngeal, and esophageal phases of swallowing were abnormal in 24%, 51%, and 73% of patients, respectively. The frequency of dysfunction increased with age for each phase of swallowing. Both the Swallowing Severity Score (a measure of dysfunction on barium swallow) and the Oral Muscle Composite Score (a reflection of vocal strength, oral-facial movement, and tongue and lip function) increased (that is, worsened) with the number of years that a patient was not receiving treatment with cysteamine, the cystine-depleting agent of choice in cystinosis. The severity scores decreased with the number of years on cysteamine therapy. The Swallowing Severity Score varied directly with the severity of muscle disease, but was not correlated with the presence or absence of the 57-kb CTNS deletion that commonly occurs in nephropathic cystinosis patients. We conclude that swallowing dysfunction in cystinosis presents a risk of fatal aspiration, correlates with the presence of muscle atrophy, and, based on cross-sectional data, increases in frequency with age and number of years without cysteamine treatment. Cystine-depleting therapy with cysteamine should be considered the treatment of choice for both pre- and posttransplant cystinosis patients.

Pharmacological treatment of nephropathic cystinosis with cysteamine

Cystinosis, clinically recognised since 1903, is an autosomal recessive lysosomal storage disease caused by mutations in CTNS. This gene codes for a lysosomal cystine transporter, whose absence leads to intracellular cystine crystals, widespread cellular destruction, renal Fanconi syndrome in infancy, renal glomerular failure in later childhood and other systemic complications. Before the availability of kidney transplantation, patients affected with cystinosis uniformly died during childhood. After solid organ transplantations became successful in the 1960s, cystinosis patients survived, but eventually developed life-threatening consequences of the disease (e.g., swallowing disorders). Since the introduction of cysteamine into the pharmacological management of cystinosis, well-treated adolescent and young adult patients have experienced normal growth and maintenance of renal glomerular function. Oral cysteamine therapy is given at doses of 60 - 90 mg/kg/day q.i.d. every 6 h, and generally achieves approximately 90% depletion of cellular cystine, as measured in circulating leucocytes. Cysteamine (and kidney transplantation) have commuted the death sentence of cystinosis into a nearly normal life with a chronic disease. Because treatment with oral cysteamine can prevent, or significantly delay, the complications of cystinosis, early and accurate diagnosis, as well as proper treatment, is critical.

Idiopathic intracranial hypertension in cystinosis

OBJECTIVES

To report a high frequency of idiopathic intracranial hypertension (IIH) in patients with cystinosis and to speculate on the relationship between these two disorders.

STUDY DESIGN

Retrospective case series and review of the literature regarding risk factors for the development of IIH in cystinosis.

RESULTS

Eight patients with cystinosis had documented papilledema, normal neuroimaging of the brain, cerebrospinal fluid (CSF) opening pressure greater than 200 mm of H2O, and normal CSF composition. No common medication, condition, or disease except cystinosis was found in these persons. Six of the patients had received prednisone, growth hormone, cyclosporine, oral contraceptives, vitamin D, or levothyroxine at the time of onset of IIH. Five patients had previous renal transplants.

CONCLUSION

No single risk factor for the development of IIH linked IIH to cystinosis in our patients. However, thrombosis susceptibility as a result of renal disease or impaired CSF reabsorption in the arachnoid villi as a result of cystine deposition might lead to the development of IIH in cystinosis.

Long-term follow-up of well-treated nephropathic cystinosis patients

We report the excellent clinical outcomes of siblings with nephropathic cystinosis treated diligently with cysteamine starting at 20 months and 2 months of age. Now 15 and 8 years old, they have glomerular filtration rates of 78 and 105 mL/min/1.73m 2 , respectively. These cases illustrate the critical importance of early diagnosis and treatment.

CTNS mutations in African American patients with cystinosis

Cystinosis, an autosomal recessive lysosomal storage disorder, is rarely diagnosed in African Americans. The disease results from mutations in the gene CTNS; at least 55 such mutations have been reported. By far the most common is a 57,257-bp deletion of Northern European origin encompassing most of the CTNS gene. We performed mutation analysis on DNA from four African American patients with cystinosis. In one individual with classical, nephropathic cystinosis, we identified a new molecular defect, i.e., a homozygous GT-->CC substitution at the +5 position of IVS 5 of CTNS (IVS 5+5 GT-->CC). The out-of-frame splicing of exon 5 creates a null allele consistent with the patient's severe phenotype. Two patients were heterozygous and one homozygous for the common 57-kb deletion allele, reflecting the admixture of African and Northern European gene pools in North America. The two African Americans heterozygous for the 57-kb deletion were also hemizygous for a 928G-->A change, associated with ocular or nonnephropathic cystinosis. These two individuals are the only known African Americans with ocular cystinosis. We conclude that the diagnosis of cystinosis should be entertained in African Americans with symptoms of the disease, and that mutation analysis for the 57-kb deletion should be considered in this group of patients.

Oral motor dysfunction and feeding difficulties in nephropathic cystinosis

Nephropathic cystinosis is a genetic disorder in which the amino acid cystine accumulates in lysosomes, resulting in multiorgan dysfunction. Progressive neuromuscular dysfunction, with bulbar and upper extremity weakness, has been described in adults with this disorder. The purpose of the present study was to determine whether there was evidence of early bulbar involvement, suggested by feeding difficulties or oral motor dysfunction in these patients, and whether the feeding and oral motor problems were associated with other evidence of neurologic dysfunction. Twenty-two children and adolescents with nephropathic cystinosis were studied. Parents completed questionnaires on feeding history and oral motor problems. Eighteen patients were given an oral motor examination, and 14 received a complete neurologic examination. The majority of children had a history of feeding difficulties. Seven children required a gastrostomy tube. Abnormalities on oral motor examination included hypotonia, abnormal gag reflex, and throaty or congested voice. Abnormalities on neurologic examination included hypotonia, muscle weakness, gross and fine motor dysfunction, and ataxia. The results indicate that feeding difficulties and oral motor dysfunction are common in children with cystinosis and appear to correlate with the general degree of neurologic dysfunction. Long-term follow-up is necessary to determine whether the early oral motor problems predict the later development of the progressive myopathy observed in adults with cystinosis.

Pulmonary dysfunction in adults with nephropathic cystinosis

OBJECTIVE

To characterize the pulmonary dysfunction in patients with nephropathic cystinosis after renal transplantation.

DESIGN

Cross-sectional analysis of consecutive adult patients.

PATIENTS

Twelve adult, nephropathic cystinosis patients and 3 adult, ocular, nonnephropathic cystinosis patients admitted to the National Institutes of Health Clinical Center.

RESULTS

The 12 nephropathic cystinosis patients (age range, 21 to 40 years) showed an extraparenchymal pattern of restrictive lung disease, with inspiratory and expiratory dysfunction. Specifically, the mean FVC was 58% of predicted, the mean FEV(1) was 57% of predicted, and the mean total lung capacity was 66% of predicted, while the mean residual volume was normal. Furthermore, the mean maximal inspiratory pressure for the eight patients tested was 40% of predicted, and the mean maximal expiratory pressure was 26% of predicted. Two patients died of respiratory insufficiency. All the patients had lived at least 17 years, while lacking compliant cystine-depleting therapy with oral cysteamine. Seven patients had a conical chest, restricting excursion, and 10 of the 12 patients had evidence of the myopathy that typifies late cystinosis. In fact, the severity of pulmonary disease correlated directly with the severity of myopathy in our group of 12 patients. In contrast, the lung parenchyma was essentially normal, as gauged by chest radiographs and CT scans of the lung. The three patients with nonnephropathic cystinosis displayed entirely normal pulmonary function.

CONCLUSION

The distal myopathy characteristic of nephropathic cystinosis results in an extraparenchymal pattern of restrictive lung disease in adults who have not received long-term cystine depletion. Whether or not oral cysteamine therapy can prevent this complication remains to be determined.

Corneal crystals in nephropathic cystinosis: natural history and treatment with cysteamine eyedrops

Although renal disease is the most prominent feature of the lysosomal storage disease cystinosis, corneal cystine crystal formation remains a major complication, leading to photophobia, corneal erosions, and keratopathies. Moreover, the extent of corneal crystal accumulation reflects the course and severity of the disease itself, and the cornea is accessible to direct examination. Therefore, we employed a scoring system, based on a library of slit-lamp photographs of corneas with increasing crystal densities (0.00-3.00), to assess the degree of crystal accumulation in 170 patients with nephropathic cystinosis examined at the National Institutes of Health between 1976 and 2000. None of the patients had received topical cystine-depleting therapy at the time of the evaluation. In this natural history study, infants in the first year of life had absent or minimal corneal crystals, i.e., a corneal cystine crystal score (CCCS) of 0 or 0.25. However, the CCCS increased linearly with age, such that every patient had visible crystals by 16 months of age, and plateaued at approximately 3.00 by early adolescence. Longitudinal studies in representative patients support the cross-sectional results. Individuals homozygous for the common 57-kb deletion involving the cystinosis gene (CTNS) displayed the same course of corneal crystal accumulation as did individuals not bearing the large deletion. Patients with ocular or nonnephropathic cystinosis had CCCSs that were, in general, half those expected for patients with nephropathic cystinosis of the same age. Administration of 0.55% cysteamine eyedrops, given 6 to 12 times per day, dissolved corneal cystine crystals in 10 representative patients with nephropathic cystinosis aged 1 to 32 years within 8 to 41 months.

The genomic region encompassing the nephropathic cystinosis gene (CTNS): complete sequencing of a 200-kb segment and discovery of a novel gene within the common cystinosis-causing deletion

Nephropathic cystinosis is an autosomal recessive disorder caused by the defective transport of cystine out of lysosomes. Recently, the causative gene (CTNS) was identified and presumed to encode an integral membrane protein called cystinosin. Many of the disease-associated mutations in CTNS are deletions, including one >55 kb in size that represents the most common cystinosis allele encountered to date. In an effort to determine the precise genomic organization of CTNS and to gain sequence-based insight about the DNA within and flanking cystinosis-associated deletions, we mapped and sequenced the region of human chromosome 17p13 encompassing CTNS. Specifically, a bacterial artificial chromosome (BAC)-based physical map spanning CTNS was constructed by sequence-tagged site (STS)-content mapping. The resulting BAC contig provided the relative order of 43 STSs. Two overlapping BACs, which together contain all of the CTNS exons as well as extensive amounts of flanking DNA, were selected and subjected to shotgun sequencing. A total of 200,237 bp of contiguous, high-accuracy sequence was generated. Analysis of the resulting data revealed a number of interesting features about this genomic region, including the long-range organization of CTNS, insight about the breakpoints and intervening DNA associated with the common cystinosis-causing deletion, and structural information about five genes neighboring CTNS (human ortholog of rat vanilloid receptor subtype 1 gene, CARKL, TIP-1, P2X5, and HUMINAE). In particular, sequence analysis detected the presence of a novel gene (CARKL) residing within the most common cystinosis-causing deletion. This gene encodes a previously unknown protein that is predicted to function as a carbohydrate kinase. Interestingly, both CTNS and CARKL are absent in nearly half of all cystinosis patients (i.e., those homozygous for the common deletion). [The sequence data described in this paper have been submitted to the GenBank data library under accession nos. AF168787 and AF163573.]

Ocular nonnephropathic cystinosis: clinical, biochemical, and molecular correlations

Ocular nonnephropathic cystinosis, a variant of the classic nephropathic type of cystinosis, is an autosomal recessive lysosomal storage disorder characterized by photophobia due to corneal cystine crystals but absence of renal disease. We determined the molecular basis for ocular cystinosis in four individuals. All had mutations in the cystinosis gene CTNS, indicating that ocular cystinosis is allelic with classic nephropathic cystinosis. The ocular cystinosis patients each had one severe mutation and one mild mutation, the latter consisting of either a 928 G-->A (G197R) mutation or an IVS10-3 C-->G splicing mutation resulting in the insertion of 182 bp of IVS10 into the CTNS mRNA. The mild mutations appear to allow for residual CTNS mRNA production, significant amounts of lysosomal cystine transport, and lower levels of cellular cystine compared with those in nephropathic cystinosis. The lack of kidney involvement in ocular cystinosis may be explained by two different mechanisms. On the one hand (e.g. the G197R mutation), significant residual cystinosin activity may be present in every tissue. On the other hand (e.g. the IVS 10-3 C-->G mutation), substantial cystinosin activity may exist in the kidney because of that tissue's specific expression of factors that promote splicing of a normal CTNS transcript. Each of these mechanisms could result in minimally reduced lysosomal cystine transport in the kidneys.

Identification and detection of the common 65-kb deletion breakpoint in the nephropathic cystinosis gene (CTNS)

The most common mutation in the cystinosis gene, CTNS, is a 65-kb deletion thought to have originated in Germany. Although homozygotes for this deletion are detectable by the absence of the D17S829 polymorphic marker, no method exists to identify heterozygotes. We identified the 65-kb deletion breakpoints and used flanking PCR primers to amplify a 423-bp fragment present only in the deletion alleles. Using this method, we determined that 121 of 216 (56%) cystinosis alleles examined bore the 65-kb deletion. We found no non-Europeans with the deletion, and the deletion size and breakpoints appeared identical in all patients studied, supporting the concept of a founder effect. The addition of D17S829 primers (266 bp apart) to the PCR created a multiplex PCR system useful for diagnosing cystinosis patients homozygous and heterozygous for the 65-kb deletion.

CTNS mutations in an American-based population of cystinosis patients

Nephropathic cystinosis is an autosomal recessive lysosomal storage disease characterized by renal failure at 10 years of age and other systemic complications. The gene for cystinosis, CTNS, has 12 exons. Its 2.6-kb mRNA codes for a 367-amino-acid putative cystine transporter with seven transmembrane domains. Previously reported mutations include a 65-kb "European" deletion involving marker D17S829 and 11 small mutations. Mutation analysis of 108 American-based nephropathic cystinosis patients revealed that 48 patients (44%) were homozygous for the 65-kb deletion, 2 had a smaller major deletion, 11 were homozygous and 3 were heterozygous for 753G-->A (W138X), and 24 had 21 other mutations. In 20 patients (19%), no mutations were found. Of 82 alleles bearing the 65-kb deletion, 38 derived from Germany, 28 from the British Isles, and 4 from Iceland. Eighteen new mutations were identified, including the first reported missense mutations, two in-frame deletions, and mutations in patients of African American, Mexican, and Indian ancestry. CTNS mutations are spread throughout the leader sequence, transmembrane, and nontransmembrane regions. According to a cystinosis clinical severity score, homozygotes for the 65-kb deletion and for W138X have average disease, whereas mutations involving the first amino acids prior to transmembrane domains are associated with mild disease. By northern blot analysis, CTNS was not expressed in patients homozygous for the 65-kb deletion but was expressed in all 15 other patients tested. These data demonstrate the origins of CTNS mutations in America and provide a basis for possible molecular diagnosis in this population.

Cardiomyopathy in a male with cystinosis

Cystinosis is a lysosomal storage disease classically associated with renal failure, photophobia, and hypothyroidism. Multi-organ dysfunction tends to develop over time, a factor of increasing significance as patient survival improves. Herein, we describe a male patient with cystinosis who developed a restrictive cardiomyopathy associated with myocardial cystine deposition and an ap-proximately 1000-fold elevation in myocardial cystine levels. Renal failure necessitated a kidney transplant at age 12. At age 31, the patient was diagnosed with progressive cardiac failure poorly responsive to aggressive antifailure therapy and risk factor modification. The patient died at age 33 in hypovolemic shock due to a ruptured pseudoaneurysm at an old renal transplant site.

Clinical polymorphism of cystinosis encephalopathy. Results of treatment with cysteamine

Of the 26 cystinotic patients over 19 years of age followed in our institution, 7 developed CNS complications at a mean age of 23 years. Two forms were observed. The first, associating cerebellar and pyramidal signs, mental deterioration and finally pseudo-bulbar palsy, may be called cystinosis encephalopathy. The other form resembled a stroke-like episode with coma and hemiplegia or milder symptoms. Hydrocephalus was rare and not associated with clinical symptoms in this series. Cysteamine was administered for longer than 6 months to 4 of the patients with encephalopathy. Two had an almost complete disappearance of their symptoms including the gross abnormalities of MR imaging in one; one improved partially and remained stable, and one continued to deteriorate but was suspected of non-compliance. These results suggest that cysteamine may be an effective treatment of cystinosis encephalopathy and encourage prescription of this drug in cystinosis in order to prevent this complication.

The objective rating of oral-motor functions during feeding

The Schedule for Oral Motor Assessment (SOMA) was developed to record oral-motor skills objectively in infants between ages 8 and 24 months postnatal. Its aim is to identify areas of dysfunction that could contribute to feeding difficulties. The procedure takes approximately 20 min to administer, and is intended to be rated largely from a videorecording of a structured feeding session. A series of foodstuffs of varying textures, including liquids, is presented to the child in a standardized manner. Oral-motor skills are evaluated in terms of discrete oral-motor movements. The schedule distinguishes these from skills at more aggregated levels of functioning such as jaw, lip, and tongue control. A total of 127 children have been studied with the instrument, including normal healthy infants and samples with nonorganic failure to thrive, and cerebral palsy. Interrater and test-retest reliabilities were determined on a subset of 10 infants who each took part in three trials rated by 2 therapists. Excellent levels of interrater reliability (kappa > 0.75) were obtained for the presence/absence of 69% of discrete oral-motor behaviors. Test-retest reliability was similarly excellent for 85% of ratable behaviors. For the first time an assessment of oral-motor functioning has been shown to have adequate reliability for children aged 8-24 months. The validation of the SOMA on a large sample of normally developing infants and its application to clinical groups is presented in an accompanying paper [1].

Cystinosis and gingival hyperplasia: demonstration of cystine crystals in gingival tissue and unusual aspects of management

A patient with nephropathic cystinosis developed gingival hyperplasia secondary to cyclosporine-A therapy for his renal allograft. The typical crystals described on electron microscopic examination of other organs of patients with cystinosis were seen in the resected gingiva of this patient. These crystals have not been previously described in this location. Unusual aspects of the management of this patient are discussed.

Distal vacuolar myopathy in nephropathic cystinosis

Nephropathic cystinosis is a lysosomal storage disorder leading to renal failure by age 10 years. Prolonged patient survival following renal transplantation has allowed the development of previously unknown long-term complications. Muscle involvement has been reported in a single posttransplant cystinosis patient, but the range of clinical, electrophysiologic, and histologic features has not been fully described. Thirteen of 54 post-renal-transplant patients that we examined developed weakness and wasting in the small hand muscles, with or without facial weakness and dysphagia. Tendon reflexes were preserved and sensory examinations were normal. Electrophysiologic studies in 11 affected patients showed normal nerve conduction velocities and preserved sensory action potentials. The voluntary motor units in the affected distal muscles had reduced amplitude and brief duration, confirmed with quantitative electromyography in 4 patients. Biopsy of the severely affected abductor digiti minimi or extensor carpi radialis brevis muscles in 2 patients revealed marked fiber size variability, prominent acid phosphatase-positive vacuoles, and absence of fiber type grouping or inflammatory cells. Crystals of cystine were detected in perimysial cells but not within the muscle cell vacuoles. The muscle cystine content of clinically affected muscles was markedly elevated. We conclude that a distal vacuolar myopathy is a common late complication of untreated nephropathic cystinosis. Although the cause is unclear, the general lysosomal defect in this disease may also affect the lysosomes within muscle fibers.

Dysphagia diagnostics and Donner: experiences in the decade of change

Martin Donner's influence in the area of dysphagia diagnostics has spanned several decades and has provided an impetus for the evolution of advanced dysphagia diagnostics. This article presents an historical perspective of the development of ultrasound imaging and the variety of other imaging procedures to evaluate swallowing. The future of image processing for dysphagia is firmly set.

Improved renal function in children with cystinosis treated with cysteamine

BACKGROUND

The lysosomal storage disease cystinosis results in renal failure at approximately 10 years of age. Although oral cysteamine therapy is recognized to preserve kidney function, the extent of renal benefit has not been determined.

METHODS

Between 1960 and 1992, we determined 24-hour creatinine clearances in 76 children with cystinosis during 1081 admissions to the National Institutes of Health. Seventeen children were considered to have received adequate treatment with cysteamine, since they had depletion of cystine from leukocytes and began therapy before the age of 2 years; treatment lasted a mean of 7.1 years. Thirty-two children were considered to have received partial treatment, since they had poor compliance with therapy or began treatment after the age of 2; treatment lasted a mean of 4.5 years. Twenty-seven children were followed in the era before cysteamine therapy and thus never received cysteamine.

RESULTS

Of the 27 children who never received cysteamine, 16 were followed at the National Institutes of Health until renal failure occurred; their mean (+/- SD) creatinine clearance was 8.0 +/- 4.8 ml per minute per 1.73 m2 of body-surface area at a mean age of 8.3 +/- 1.9 years. Of the 17 children who received adequate treatment, none had renal failure; their mean creatinine clearance was 57 +/- 20 ml per minute per 1.73 m2 at 8.3 +/- 3.8 years of age. The mean creatinine clearance of the children who received partial or adequate treatment with cysteamine increased with age up to the age of five years and then declined linearly with age at a normal rate. For the children who received adequate treatment, the mean creatinine clearance was predicted to reach 0 ml per minute per 1.73 m2 at the age of 74 years, as compared with 20 years of age for the children who received partial treatment. With no therapy, the mean creatinine clearance reaches 0 ml per minute per 1.73 m2 at 10 years of age.

CONCLUSIONS

Children with cystinosis who are treated early and adequately with cysteamine have renal function that increases during the first five years of life and then declines at a normal rate. Patients with poorer compliance and those who are treated at an older age do less well.

Parenchymal organ cystine depletion with long-term cysteamine therapy

Nephropathic cystinosis is a lysosomal storage disorder characterized by renal failure, multisystem organ damage, and poor growth. Oral cysteamine therapy retards renal deterioration and enhances growth, but parenchymal organ cystine depletion has never been documented. We measured skeletal muscle cystine in 11 cystinosis patients not treated with cysteamine; analysis of their values plus 11 published values showed that muscle cystine increases linearly with age in cystinosis patients (slope, 0.074 nmol half-cystine/mg wet wt/year). In contrast, 15 patients treated for 4 to 11 years with oral cysteamine had a relatively constant muscle cystine content (slope, 0.004 nmol half-cystine/mg wet wt/year). The treated patients' mean muscle cystine, 0.091 +/- 0.064 (SD) nmol half-cystine/mg wet wt, was significantly less (P < 0.001) than that for the 11 youngest untreated patients, 0.754 +/- 0.534 nmol half-cystine/mg wet wt. On postmortem examination, a 9-year-old cystinosis patient treated for 8 years with oral cysteamine had liver, kidney, pancreas, lung, and spleen cystine values 5 to 90 times lower than those of an untreated age-matched control. We conclude that long-term oral cysteamine therapy routinely depletes cystinotic skeletal muscle of cystine; cysteamine is the treatment of choice for the prevention of both renal and nonrenal complications of cystinosis.

Stimulation of mucosal uptake of selenium from selenite by some thiols at various sites of rat intestine

The influence of several thiols (conc. 1 mmol/L) on mucosal uptake of 75Se from 75Se-labeled selenite (conc. 10 mumol/L) across the brush border of rat jejunum and cecum was investigated in vitro using a short-term uptake technique. L-Cysteine (L-Cys) stimulated 75Se uptake in the mid- and distal jejunum and cecum, but not in the proximal jejunum. The effect was maximal in the distal jejunum. D-Cys was less effective in the jejunum and similarly effective in the cecum. L-Leucine (L-Leu) and L-glutamic acid significantly reduced the stimulatory effect of L-Cys on Se uptake in the distal jejunum, whereas the respective effect of D-Cys was not diminished by L-Leu. Cysteamine stimulated mucosal 75Se uptake at all intestinal sites tested, whereas the effect of mercaptopyruvate was restricted to the distal jejunum. Thioglycolate also enhanced 75Se uptake in the distal jejunum. The stimulatory effects of L-Cys, mercaptopyruvate, and thioglycolate were Na(+)-dependent, whereas the effect of cysteamine also occurred in the absence of Na+. Mercaptosuccinate, D-penicillamine, ergothioneine, and thiosulfate did not enhance mucosal 75Se uptake. It is concluded from these findings that the reaction of some thiols with selenite results in Se compounds that are rapidly absorbed by the intestinal epithelium through various Na(+)-dependent and Na(+)-independent mechanisms. The high bioavailability of Se from selenite found by others might thus be the result of the presence of thiols in the gastrointestinal tract.