Severe pancytopenia at the presentation of Imerslund-Gräsbeck syndrome in a 23-month-old Italian boy.

BACKGROUND: Imerslund-Gräsbeck syndrome (IGS) is a rare autosomal recessive disorder characterized by megaloblastic anemia due to selective cobalamin malabsorption and benign proteinuria. IGS is caused by a disfunction of the cubam receptor, which mediates the reabsorption of cobalamin in the ileum and the reuptake of albumin in renal proximal tubules. CASE PRESENTATION: We describe the case of a 23-month-old-italian infant presenting with severe pancytopenia and failure to thrive in whom the diagnosis of IGS was made and vitamin B12 replacement therapy was resolutive. Genetic analysis (NGS with CNV analysis including 214 genes involved in bone marrow failure and anemia), showed the presence of two pathogenetic variants in the AMN gene (c-208-2 A > G and c.1006 + 34_1007-31del). These variants have been previously described in the literature, but their combination has never been reported. CONCLUSIONS: Imerslund-Gräsbeck syndrome should be considered in the differential diagnosis of children with severe pancytopenia even in those without neurological involvement. This case emphasizes the importance of an early diagnosis and prompt treatment, to prevent irreversible neurological injury.

Intermediate cystinosis: a case report of 10-year treatment with cysteamine.

BACKGROUND: Cystinosis is a lysosomal storage disorder characterized by an autosomal recessive phenotype. Intermediate cystinosis, which progresses slowly and causes renal failure, accounts for approximately 5% of all cystinosis cases. Patients with intermediate cystinosis may not exhibit the typical symptoms of cystinosis, such as Fanconi syndrome and ocular symptoms. Because of its diverse clinical presentation and rarity, intermediate cystinosis can be difficult to diagnose. Additionally, few patients can tolerate cystine-depleting drugs, such as cysteamine, because of their complicated administration schedules and side effects. We report a case of intermediate cystinosis that was treated with cysteamine for 10 years. CASE PRESENTATION: Urinary abnormalities were first diagnosed when the patient was 3 years of age during a health examination specifically for 3-year-old children, which is unique to Japan. Cystinosis was diagnosed when the patient was 12 years of age. Cysteamine therapy was initiated and regular cystine concentration measurements were performed. Although proteinuria persisted, the patient's renal function progressed slowly. Two renal biopsies were performed, and multinucleated podocytes and cystine crystals without focal segmental glomerulosclerosis lesions were observed in the biopsy specimens. The patient's renal function remained stable. CONCLUSIONS: This case of intermediate cystinosis was treated with cysteamine over the course of 10 years. Intermediate cystinosis requires an appropriate diagnosis and long-term treatment.

Ocular Involvement in Patients with Infantile Nephropathic Cystinosis.

Cystinosis is a rare autosomal recessive lysosomal storage disease associated with high mortality and morbidity rates. The most distinctive ocular manifestations of cystinosis are photophobia, tearing, and blurred vision. Herein, we assessed the ocular involvement of four patients from two families diagnosed with infantile nephropathic cystinosis using optical coherence tomography (OCT) and in vivo confocal microscopy (IVCM). Anterior segment OCT demonstrated multiple hyperreflective punctate deposits, and IVCM revealed needle-shaped bright crystal deposits in the corneal stroma in all patients. Three patients also had crystal deposits in the epithelium, where epithelial cell disruption was observed. Crystal deposits around the subepithelial nerve plexus were noted in some sections. In one patient, round and needle-shaped bright deposits along with inflammatory cells were observed in the limbal region of the conjunctiva. Infrared fundus images of two female siblings revealed hyperreflective crystal-like deposits around the optic disc, macula, and peripheral retina, and enhanced depth imaging OCT showed accumulation of crystals in all layers of the retina.

Cortical impairment and reduced muscle mass in children and young adults with nephropathic cystinosis.

Nephropathic cystinosis is an orphan autosomal recessive lysosomal storage disease characterized by a deficiency of cystinosin, a cystine transporter protein, leading to tissue damage, primarily in the kidney and cornea. With the introduction of cystine-depleting therapy with cysteamine and the possibility to survive to adulthood, new challenges of skeletal complications are a concern, with sparse data available regarding bone development. The aim of the current study was to gain more information on bone density and geometry in these patients. Fifty-one patients (29 males, 22 females) with genetically proven nephropathic cystinosis were clinically evaluated with a medical history, physical examination, grip strength measurements, and biochemical and imaging studies. Bone mineral density, bone geometry, and muscle cross sectional area were measured, and muscle was evaluated. Results were compared with age- and gender-specific reference data. Z-scores for height (mean [M] = -1.75, standard deviation [SD] = 1.43), weight (M = -1.67, SD = 1.29), and BMI (M = -0.98, SD = 1.29) were lower than reference data. Medullary cross-sectional area (CSA) and cortical density z-scores were not compromised (M = 0.12, SD = 1.56 and M = -0.25, SD = 1.63, respectively), but cortical CSA z-scores and Strength-Strain Index (SSI) were reduced (M = -2.16, SD = 1.08, M = -2.07, SD = 1.08). Muscular deficits were reflected by reduced z-scores for muscle CSA (M = -2.43, SD = 1.27) and grip strength (M = -3.01, SD = 1.10), along with jump force (34% lower than reference value). Multiple regression analyses indicated an association of muscle mass with medullary CSA and SSI, but not with cortical CSA. While bone density parameters were normal, bone geometry was altered, resulting in a thinner cortex with possible impact on bone strength. Muscle weakness be partially responsible for altered bone geometry and could provide a potential treatment target.

Nephropathic cystinosis is a rare lysosomal storage disease affecting primarily the kidney and cornea. With new treatment options, patients survive to adulthood and challenges such as bone development and fracture risk become a matter of concern. In this study, we investigated bone density, bone geometry, and muscle mass and function using peripheral quantitative-computed tomography. We included 51 patients with genetically proven cystinosis at an age between 6.6 and 39.6 yr. Beside height impairment and low body weight, patients had a thinner bone cortex leading to a reduced stress­strain index. This index represents the resistance of bone against torsional load and, therefore, is considered to be a good marker of bone strength: with low values fracture risk might increase. Furthermore, patients had lower muscle mass and muscle function, the latter evaluated by grip strength and jump force. Looking for the interaction of muscle and bone multiple regression analyses indicated an association of muscle mass with strength strain index. The muscle weakness might be partially responsible for altered bone geometry and lower bone strength and is possibly a treatment target, which has to be investigated in the future.

Morphological changes and their associations with clinical parameters in children with nephropathic cystinosis and chronic kidney disease prior to kidney replacement therapy over 25 years.

BACKGROUND: Infantile nephropathic cystinosis (INC) is a rare lysosomal storage disorder, mostly and often firstly affecting the kidneys, together with impaired disharmonious growth and rickets, eventually resulting in progressive chronic kidney disease (CKD). With the introduction of cysteamine therapy, most pediatric patients reach adulthood with no need for kidney replacement therapy. Still, detailed changes in INC patients' clinical and morphological presentation over the past decades have not yet been thoroughly investigated. METHODS: Two groups with a respective total of 64 children with INC and 302 children with CKD, both treated conservatively and aged 2 to 18 years, were prospectively observed in the time span from 1998 to 2022 with 1186 combined annual clinical and morphological examinations clustered into two measurement periods (1998 to 2015 and ≥ 2016). RESULTS: In INC patients, thoracic proportion indices remained markedly increased, whereas body fat stores remained decreased over the past 25 years (+ 1 vs. below ± 0 z-score, respectively). Their CKD peers presented with overall improved growth, general harmonization of body proportions, and improved body fat stores, while INC patients only presented with an isolated significant increase in leg length over time (∆0.36 z-score). eGFR adjusted for age did not significantly change over the past 25 years in both groups. Alkaline phosphatase (ALP) showed a significant decrease in CKD patients over time, while remaining above normal levels in INC patients. CONCLUSIONS: Disproportionate thoracic shape and impaired body fat stores remain the most characteristic morphological traits in INC patients over the past 25 years, while causal mechanisms remain unclear.

Fibrosing colonopathy associated with cysteamine bitartrate delayed-release capsules in cystinosis patients.

BACKGROUND: The objective of this report is to identify and characterize cases of fibrosing colonopathy, a rare and underrecognized adverse event, associated with cysteamine delayed-release (DR) in patients with nephropathic cystinosis. METHODS: We searched the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) and the medical literature for postmarketing reports of fibrosing colonopathy associated with cysteamine through August 2, 2023. RESULTS: We identified four cases of fibrosing colonopathy reported with the use of cysteamine DR. The time to onset ranged from 12 to 31 months. In one case, the patient required surgery to have a resection of a section of the strictured colon and a diverting ileostomy. Fibrosing colonopathy was diagnosed by histopathology in two of the cases. CONCLUSIONS: Our case series identified the risk of fibrosing colonopathy in patients taking cysteamine DR and prompted regulatory action by the FDA. As outlined in changes to the U.S. prescribing information for cysteamine DR, healthcare professionals should be aware of the potential risk of fibrosing colonopathy with cysteamine DR, especially as symptoms can be non-specific leading to misdiagnosis or delayed diagnosis. If the diagnosis of fibrosing colonopathy is confirmed, consideration should be given to permanently discontinuing cysteamine DR and switching to cysteamine immediate-release treatment.

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.

Renal transplantation for infantile and juvenile cystinosis: Two case report and review of the literature.

Cystinosis is a rare autosomal recessive lysosomal storage disorder characterized by cystine buildup in various tissues, including the kidneys. Renal involvement is the primary manifestation, leading to end-stage renal disease (ESRD) if left untreated. Kidney transplantation (KT) in patients with cystinosis has significantly improved their prognosis for the disease outcome. Detailed reports on preoperative and Long-term postoperative management in these patients remain sparse. This report discusses the outcomes of two young adult patients of Middle Eastern descent with cystinosis who underwent KT. The first patient, diagnosed with infantile nephropathic cystinosis treated by cystine-depleting therapy, was operated by KT at the age of 18. The second patient, diagnosed with juvenile cystinosis, underwent transplantation at the age of 35 after being treated with hemodialysis. Our report describes detailed pre- and postoperative managements, including laboratory results, and pharmacological interventions. Both cases highlighted the varying clinical manifestations and disease severity between infantile and juvenile cystinosis. Pre-transplant conditions included renal dysfunction, growth retardation, secondary hyperparathyroidism, anemia, and extrarenal manifestations. Following KT, both patients experienced regained renal function, resolution of extrarenal complications, and normalization of laboratory parameters. Furthermore, both patients showed excellent postoperative outcomes with no acute rejection or allograft-related complications. KT is the treatment of choice for cystinosis patients with ESRD. Long-term follow-up post-transplantation is crucial to maintain good graft function. Further studies may elucidate optimal pre- and postoperative management protocols for this rare condition.

Extrarenal complications of cystinosis.

Cystinosis is a rare autosomal recessive disease with an incidence 1 per 100,000-200,000 live births. It is caused by pathogenic variants of the cystinosin (CTNS) gene that lead to impaired cystine transport from lysosomes to cystosol, resulting in cystine accumulation in lysosomes and subsequent cellular dysfunction. The initial manifestation, cystine accumulation in proximal tubular cells (PTCs), causes renal Fanconi syndrome, which presents with proximal renal tubular acidosis and generalized dysfunction of the proximal tubule, including the presence of polyuria, glycosuria, phosphaturia, aminoaciduria, tubular proteinuria, growth retardation, and rickets. Eventually, glomerular involvement, glomerular proteinuria, focal segmental glomerulosclerosis (FSGS), and progression to kidney failure occur. Although the kidneys are the first organs affected, and play a key role in morbidity and mortality, extrarenal multiorgan involvement can occur in patients with cystinosis, which is seen not only in adults but in early ages in untreated patients, patients with insufficient treatment, and in those that don't comply with treatment. The treatment of cystinosis consists of supportive treatment for Fanconi syndrome, and specific lifelong cystine-depleting therapy using oral cysteamine. There is strong evidence that as early as possible, initiation and ongoing appropriate therapy with cysteamine are essential for delaying the progression to kidney failure, end-organ damage, and extrarenal involvement. The present review aimed to evaluate the extra renal complications of cystinosis.

Neurologic involvement in cystinosis: Focus on brain lesions and new evidence of four-repeat (4R-) Tau immunoreactivity.

Nephropathic cystinosis is a rare autosomal recessive storage disorder caused by CTNS gene mutations, leading to autophagy-lysosomal pathway impairment and cystine crystals accumulation. Neurologic involvement is highly variable and includes both neurodevelopmental and neurodegenerative disturbances, as well as focal neurologic deficits. By presenting longitudinal data of a 28-year-old patient with a large infratentorial lesion, we summarized the pathology, clinical and imaging features of neurological involvement in cystinosis patients. Brain damage in form of cystinosis-related cerebral lesions occurs in advanced disease phases and is characterized by the accumulation of cystine crystals, subsequent inflammation with vasculitis-like features, necrosis, and calcification. Epilepsy is a frequent comorbidity in affected individuals. Steroids might play a role in the symptomatic treatment of "stroke-like" episodes due to edematous-inflammatory lesions, but probably do not change the overall prognosis. Lifelong compliance to depleting therapy with cysteamine still represents the main therapeutic option. However, consequences of CTNS gene defects are not restricted to cystine accumulation. New evidence of four-repeat (4R-) Tau immunoreactivity suggests concurrent progressive neurodegeneration in cystinosis patients, highlighting the need of innovative therapeutic strategies, and shedding light on the crosstalk between proteinopathies and autophagy-lysosomal system defects. Eventually, emerging easily accessible biomarkers such as serum neurofilament light chains (NfL) might detect subclinical neurologic involvement in cystinosis patients.

Impact of compliance to oral cysteamine treatment on the costs of Kidney failure in patients with nephropathic cystinosis in the United Kingdom.

BACKGROUND: Nephropathic Cystinosis (NC), a rare disease characterised by intra-lysosomal accumulation of cystine, results in progressive kidney failure (KF). Compliance to lifelong oral cysteamine, the only therapy, is often compromised. The relationship between compliance and costs of NC has not been previously formally assessed. The present study evaluates the impact of compliance on lifetime (direct) costs of treating KF in NC patients in the United Kingdom. METHODS: A three-state (KF-free, post-KF, death) partitioned survival model was developed for hypothetical 'Good Compliance' (GC) and 'Poor Compliance' (PC) cohorts. Survival in the KF-free state was determined by a published regression function of composite compliance score (CCS). The CCS is a summation of annual compliance scores (ACS) over treatment duration prior to KF. ACSs are indexed on annual (average) leukocyte cystine levels (LCL). The Poor Compliance cohort was defined to reflect NC patients in a previous study with a mean LCL of 2.35 nmols nmol half-cystine/mg protein over the study period - and an estimated mean ACS of 1.64 over a 13.4 year treatment duration. The Good Compliance cohort was assumed to have an ACS of 2.25 for 21 years. Major KF costs were evaluated - i.e., dialysis, kidney transplants, and subsequent monitoring. RESULTS: The mean CCS was 47 for the GC and 22 for the PC cohort respectively, corresponding to estimated lifetime KF costs of £92,370 and £117,830 respectively - i.e., a cost saving of £25,460/patient, or £1,005/patient for every 1-unit improvement in CCS. CONCLUSION: This analysis indicates that lifetime costs of KF in NC can be reduced through improved treatment compliance with oral cysteamine.

Chest configuration in children and adolescents with infantile nephropathic cystinosis compared with other chronic kidney disease entities and its clinical determinants.

BACKGROUND: Infantile nephropathic cystinosis (INC) is a systemic lysosomal storage disease causing intracellular cystine accumulation, resulting in renal Fanconi syndrome, progressive kidney disease (CKD), rickets, malnutrition, and myopathy. An INC-specific disproportionately diminished trunk length compared to leg length poses questions regarding the functionality of the trunk. METHODS: Thus, we prospectively investigated thoracic dimensions and proportions, as well as their clinical determinants in 44 pediatric patients with INC with CKD stages 1-5 and 97 age-matched patients with CKD of other etiology between the ages of 2-17 years. A total of 92 and 221 annual measurements of patients with INC and CKD, respectively, were performed, and associations between anthropometric and clinical parameters were assessed using linear mixed-effects models. RESULTS: Patients with INC exhibited altered chest dimensions that were distinct from CKD controls, characterized by markedly increased chest depth to height and chest depth to chest width ratio z-scores (> 1.0), while those of patients with CKD were only mildly affected (z-score within ± 1.0). Ratio z-scores differed significantly between both patient groups from 2-6 years of age onward. The degree of chest disproportion in INC patients was significantly associated with both the degree of CKD and tubular dysfunction (e.g., low serum phosphate and bicarbonate) across three different age groups (2-6, 7-12, and 13-17 years). CONCLUSION: Our data show an INC-specific alteration in thoracic shape from early childhood onward, which is distinct from CKD of other etiologies, suggesting early childhood subclinical changes of the musculoskeletal unit of the thoracic cage, which are associated with kidney function. A higher resolution version of the Graphical abstract is available as Supplementary information.

[Cystinosis: From the gene identification to the first gene therapy clinical trial]. / Cystinose - De la découverte du gène aux premiers essais de thérapie génique.

Cystinosis is an autosomal recessive metabolic disease characterized by lysosomal accumulation of cystine in all the cells of the body. Infantile cystinosis begins in infancy by a renal Fanconi syndrome and eventually leads to multi-organ failure, including the kidney, eye, thyroid, muscle, and pancreas, eventually causing premature death in early adulthood. The current treatment is the drug cysteamine that only delays the progression of the disease. We identified the gene involved, CTNS, and showed that the encoded protein, cystinosin, is a proton-driven cystine transporter. We generated a mouse model of cystinosis, the Ctns-/- mice, that recapitulates the main disease complications. The goal was next to develop a gene therapy approach for cystinosis. We used bone marrow stem cells as a vehicle to bring the healthy CTNS gene to tissues, and we showed that wild-type hematopoietic stem and progenitor cell (HSPC) transplantation led to abundant tissue integration of bone marrow-derived cells, significant decrease of tissue cystine accumulation and long-term kidney, eye and thyroid preservation. We then developed an autologous transplantation approach of HSPCs modified ex vivo using a lentiviral vector to introduce a functional CTNS cDNA, and showed its efficacy in Ctns-/- mice. We conducted the pharmacology/toxicology studies, developed the manufacturing process using human CD34+ cells, and design the clinical trial. We received Food and Drug Administration (FDA)-clearance to start a phase 1/2 clinical trial for cystinosis in December 2018. Six patients have been treated so far. In this review, we describe the path to go from the gene to a gene therapy approach for cystinosis.

Title: Cystinose - De la découverte du gène aux premiers essais de thérapie génique. Abstract: La cystinose est une maladie métabolique autosomique récessive caractérisée par une accumulation lysosomale de cystine dans toutes les cellules de l'organisme. La cystinose infantile débute dans la petite enfance par un syndrome de Fanconi et aboutit à une détérioration progressive de la fonction de la plupart des organes, y compris les reins, les yeux, la thyroïde, les muscles et le pancréas, et finit par entraîner une mort prématurée. Le traitement par la cystéamine ne permet que de retarder la progression de la maladie. Afin de développer une approche de thérapie génique pour la cystinose, un modèle murin qui présente les principales complications de la maladie a été développé grâce à l'identification du gène CTNS, dont le produit, la cystinosine, est un co-transporteur de cystine-protons. Cette revue décrit les étapes allant de la découverte du gène à la thérapie génique pour la cystinose, qui a permis de traiter six patients jusqu'à présent.

Inherited Fanconi syndrome.

BACKGROUND: Fanconi-Debré-de Toni syndrome (also known as Fanconi renotubular syndrome, or FRST) profoundly increased the understanding of the functions of the proximal convoluted tubule (PCT) and provided important insights into the pathophysiology of several kidney diseases and drug toxicities. DATA SOURCES: We searched Pubmed and Scopus databases to find relevant articles about FRST. This review article focuses on the physiology of the PCT, as well as on the physiopathology of FRST in children, its diagnosis, and treatment. RESULTS: FRST encompasses a wide variety of inherited and acquired PCT alterations that lead to impairment of PCT reabsorption. In children, FRST often presents as a secondary feature of systemic disorders that impair energy supply, such as Lowe's syndrome, Dent's disease, cystinosis, hereditary fructose intolerance, galactosemia, tyrosinemia, Alport syndrome, and Wilson's disease. Although rare, congenital causes of FRST greatly impact the morbidity and mortality of patients and impose diagnostic challenges. Furthermore, its treatment is diverse and considers the ability of the clinician to identify the correct etiology of the disease. CONCLUSION: The early diagnosis and treatment of pediatric patients with FRST improve the prognosis and the quality of life.

Corneal Manifestation in Patients with Infantile Nephropathic Cystinosis.

Nephropathic cystinosis is a rare autosomal recessive disease caused by mutations in the CTNS gene. This causes dysfunction of cystinosin, a protein that transports cystine out of lysosomes, causing cystine crystals to accumulate in cells in most organ systems. While renal complications predominate in the early forms of cystinosis, corneal crystal accumulation will inevitably manifest in all patients. The main symptoms are photophobia along with glare sensitivity and blepharospasm. In addition, corneal crystal accumulation can cause other complications, such as recurrent corneal erosions, punctate or filamentary keratopathy, and chronic dry eye. Eventually, peripheral corneal neovascularization and limbal stem cell deficiency may develop. Ophthalmologists play a key role in the early diagnosis of patients with cystinosis. This review aims to not only raise awareness of secondary complications of corneal crystal accumulation, but also to highlight current treatment options and challenges that ophthalmologists and pediatricians might face.