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

Pediatric cystinosis: Corneal cystine deposits and papilledema in a 4-year-old: A case report

Cystinosis is a rare autosomal recessive lysosomal storage disorder characterized by the accumulation of cystine within lysosomes, leading to multi-systemic complications. The present study describes the case details (the presentation and management) of a 4-year-old female child diagnosed with infantile cystinosis, further complicated by distal renal tubular acidosis and stage 4 chronic kidney disease. The patient exhibited significant ocular manifestations, notably bilateral corneal cystine crystal deposits, observed as a shimmering effect under slit-lamp biomicroscopy and marked papilledema in both eyes. Fundoscopic examination also revealed retinal cystine deposits, indicating systemic involvement. The systemic complications included renal dysfunction requiring ongoing dialysis and bicarbonate supplementation to manage metabolic acidosis, as well as elevated intracranial pressure. Ophthalmological management focused on vision preservation through corrective lenses and topical cysteamine eye drops to reduce corneal cystine accumulation. Regular follow-up appointments were scheduled to monitor corneal clarity and optic nerve health. The case described herein underscores the complexity of cystinosis and the critical need for a multidisciplinary approach involving ophthalmology, nephrology, and neurology. Early diagnosis and timely therapeutic interventions are essential to mitigate the progressive nature of the disease and improve patient outcomes. The present case report also highlights the challenges in managing the condition, including treatment adherence and potential complications, and emphasizes the importance of continued research to develop more effective therapies and improve the quality of life for affected individuals.

Long-term outcomes in nephropathic cystinosis: a review

Nephropathic cystinosis is a lysosomal storage disease due to biallelic pathogenic variants in the CTNS gene encoding the cystine transport protein cystinosin. Dysfunction of cystinosin results in the intralysosomal accumulation of the disulfide cystine, which crystallizes in some tissues and damages many parenchymal organs. Fanconi syndrome is the first presenting sign with all the features of generalized proximal tubular dysfunction. The natural history of cystinosis includes multisystem complications, the most prominent being glomerular failure at 9-10 years. If a kidney transplant prolongs life, other complications occur, with variable frequencies. Some of the most common are hypothyroidism, a distal vacuolar myopathy, pancreatic exocrine and endocrine insufficiency, male hypogonadism, and idiopathic intracranial hypertension. Cystinosis is diagnosed biochemically by measuring the cystine content of leucocyte and molecularly by identifying pathogenic variants in CTNS. Prenatal diagnosis is available. Treatment consists of replacement of kidney tubular losses, symptomatic management of systemic complications, and specific therapy directed at the basic defect, i.e., lysosomal cystine accumulation. This involves the free thiol cysteamine, which can deplete approximately 95% of the lysosomal cystine content. Oral cysteamine therapy has extended the time to kidney failure by approximately 7 years (to a mean of 16 years) and mitigates or prevents late complications of the disease. In addition, cysteamine eyedrops can dissolve corneal cystine crystals within months. Nevertheless, the mean age at death for individuals born between 1985 and 1999 has been 29 years, and earlier diagnosis by newborn screening, treatment with more palatable cystine-depleting agents, and trials with gene therapy are critical current pursuits.

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.

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.

Cystinosis in Pediatric Renal Transplant Recipients: A Case-Control Study From Kuwait

OBJECTIVES

Cystinosis is the most frequent cause of the inherited renal Fanconi syndrome and is also potentially treatable. In this study, we have reported our single-center experience of the longterm outcomes of kidney transplant in patients with cystinosis.

MATERIALS AND METHODS

Pediatric patients with cystinosis (n = 17) were compared with a matched control group without cystinosis (n = 126). The 2 groups were compared with regard to demographic data, posttransplant complications, and graft and patient outcomes.

RESULTS

Most patients with cystinosis were male teenagers (52.9%) with comparable mean age (12.4 ± 4.1 vs 14 ± 3.1 years) versus the group without cystinosis. The 2 study groups were comparable with regard to type of dialysis, type of donor, blood group, and pretransplant comorbidities (P > .05). Patients with cystinosis received significantly more potent induction therapy (P < 0.05), but both groups were maintained on comparable immunosuppressive regimens (mostly tacrolimus based) (P > .05). Most grafts in both groups displayed immediate graft function. The percentage of patients with cystinosis with primary graft function was significantly higher than the percentage of those patients without cystinosis who had primary graft function (P = .024); this was associated with a relatively lower baseline creatinine level, although this was not significant (P > .05). Posttransplant complications, especially posttransplant diabetes, cytomegalovirus viremia, or BK nephropathy, were comparable (P > .05). Moreover, patient and graft survival rates were similar in the 2 groups (P > .05).

CONCLUSIONS

Under standard immunosuppression, renal transplant and cysteamine therapy were safe with good long-term outcomes in patients with cystinosis. Studies that can include more patients and that have longer follow-up are needed to better understand the nature of this genetic disease and to discover the best treatment options.

Fertility in Cystinosis

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

Ophthalmic Evaluation of Diagnosed Cases of Eye Cystinosis: A Tertiary Care Center's Experience

Background: We aimed to identify diagnosed cases of ocular cystinosis and describe clinical, epidemiological and therapeutic characteristics. Methods: This is a descriptive and retrospective case series. All patients underwent a full check-up examination every 4–6 months by ophthalmologists, nephrologists and other required specialists. Results: Of the seven cases, six (85.7%) were females and one (14.2%) was male. The infantile nephropathic form of cystinosis was observed in five patients and the juvenile nephropathic form in two patients. No patients with the ocular form of cystinosis were identified. Corneal cystine crystals (CCC) were found in all analyzed patients. Severe ocular and general complications of the disease that had been standing for years, connected to the infantile nephropathic form, delayed diagnosis or inappropriate treatment, were observed only in two patients. All patients received topical therapy. No adverse events related to the therapy were observed. Conclusions: Cystinosis is a rare, progressive disease. Early diagnosis and treatment prevent serious complications from numerous systemic organs. Patients require constant systematic monitoring by various specialists.

Latest Clinical Approaches in the Ocular Management of Cystinosis: A Review of Current Practice and Opinion from the Ophthalmology Cystinosis Forum

Cystinosis, a rare autosomal recessive disease caused by intracellular cystine accumulation, occurs in an estimated 1/100,000-200,000 live births. Ocular non-nephropathic cystinosis is typically diagnosed during adulthood, when patients present with corneal crystal deposition and no systemic involvement. Due to the rarity of the condition, diagnosis is often delayed and can have a significant impact on the overall prognosis of the disease. Early diagnosis is therefore imperative to ensure successful treatment and improve quality of life, as most of its clinical manifestations can be prevented or delayed. Early detection strategies and practical approaches for the ocular management of cystinosis were discussed during the Ophthalmology Cystinosis Forum, a 1-day meeting held in Berlin, Germany during June 2017. Recommendations for early detection comprise ophthalmic assessment, including self- and clinician-assessed recording of photophobia, and visual acuity, slit-lamp examination and tonometry ophthalmic examinations. In vivo confocal microscopy and anterior segment optical coherence tomography were highlighted as valuable techniques in evaluating cystine crystals in the cornea, in vivo and non-invasively. The mainstay of ocular cystinosis treatment is the cystine-depleting aminothiol cysteamine. Indeed, early treatment with and strict adherence to cysteamine therapy has a considerable impact on the long-term prognosis of ocular cystinosis. In rare diseases such as ocular cystinosis, standardised guidelines and recommendations for detection, patient care and follow-up assessments are essential. Such guidelines provide a support tool for healthcare professionals caring for ocular cystinosis patients. Multidisciplinary teams (MDTs) are essential for delivering gold standard care and improving quality of life for patients and their families. This review paper highlights current early detection policies, clinical treatment strategies and practical approaches for the ocular management of cystinosis, including implementing a cystinosis MDT. Additionally, discussions of the Ophthalmology Cystinosis Forum held in 2017 are summarised. FUNDING: Orphan Europe. Plain language summary available for this article.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0633-3) contains supplementary material, which is available to authorized users.

Clinical Practice: A Proposed Standardized Ophthalmological Assessment for Patients with Cystinosis

Cystinosis is a rare autosomal recessive disease with an incidence of approximately 1 case per 100,000–200,000 live births. Over the years, gaining in-depth knowledge of the disease has led to vast improvement in patient life expectancy. However, debilitating, extra-renal manifestations such as eye disease, in particular corneal crystal deposition and its associated photophobia, still occur frequently, regardless of patient age and notwithstanding the increased implementation of systemic therapy. Ophthalmological assessment has not yet been standardized. The aim of this article was to provide clear recommendations for ophthalmological assessment during follow-up of patients with cystinosis to improve quality and regularity of ophthalmological care and thereby minimize ophthalmological complications. A literature search was performed to assess previous and current recommendations on examinations to conduct during follow-up of patients with cystinosis. Multidisciplinary cystinosis clinics were set up in collaboration with the Department of Ophthalmology and the Department of Pediatric Nephrology to allow patients to be seen by a nephrologist, an ophthalmologist and other specialists on the same day. Based on the results of these multidisciplinary clinics the standardized clinical ophthalmological assessment was drafted. This is a protocol for follow-up, describing the approach taken regarding ophthalmological follow-up of patients with cystinosis, considering the different types of the disease and the time since diagnosis. Standard examination includes history, visual acuity, tonometry and slit-lamp examination, with fundus photography performed at diagnosis and annually thereafter. Confocal microscopy is the imaging modality of choice, while anterior segment optical coherence tomography (OCT) is a good alternative. Finally, posterior segment OCT for imaging of the macular region and optic nerve should be conducted on an annual basis.

Ophthalmic clues to the endocrine disorders

PURPOSE

Eye is a vital sense organ and reflects the physical and mental wellbeing of a person. Detailed examination of the eye is an essential part in the clinical evaluation of patients with any systemic disorder. The interaction between ophthalmologists and endocrinologists is often limited to Graves' ophthalmopathy and diabetic retinopathy. However, there are many ophthalmic manifestations, which are characteristically seen in endocrine disorders. In this review, we shall discuss the ocular manifestations of the endocrine syndromes excluding the Graves' ophthalmopathy and diabetic retinopathy.

METHODS

We performed a PubMed search of articles published in English showing the ophthalmic features in the endocrine disorders. Relevant cited articles were also retrieved.

RESULTS

Most of the publications included in the review were case reports and review articles. Many endocrine disorders have characteristic manifestations pertaining to the various structures of the eye. The involvement is seen from the external structures of the eye to the inner most layers of the retina. Many ocular-endocrine syndromes also exist with characteristic clues to the clinical diagnosis.

CONCLUSION

The endocrinologists need to be aware of these ocular signs that help in the early diagnosis of the underlying disorder. A syndromic approach is essential in the diagnosis of endocrinopathy in patients presenting with ophthalmic features.

Structured Transition Protocol for Children with Cystinosis

The transition from pediatric to adult medical services has a greater impact on the care of adolescents or young adults with chronic diseases such as cystinosis. This transition period is a time of psychosocial development and new responsibilities placing these patients at increased risk of non-adherence. This can lead to serious adverse effects such as graft loss and progression of the disease. Our transition protocol will provide patients, families, physicians, and all those involved a structured guide to transitioning cystinosis patients. This structured protocol depends on four areas of competency: Recognition, Insight, Self-reliance, and Establishment of healthy habits (RISE). This protocol has not been tested and therefore challenges not realized. With a focus on medical, social, and educational/vocational aspects, we aim to improve transition for cystinosis patients in all aspects of their lives.