Intracranial Hypertension in Cystinosis Is a Challenge: Experience in a Children's Hospital

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.

Posterior Segment Involvement in Infantile Nephropathic Cystinosis - A Review

Cystinosis is a rare lysosomal storage disease with a prevalence of 1 : 100 000 - 1 : 200 000 cases. It is caused by biallelic mutations in the CTNS gene, which encodes cystinosin, that transport cystine out of the lysosomes. Due to its dysfunction, cystine crystals accumulate in the lysosomes and ultimately cause apoptosis of the cell. Since cystinosin is ubiquitously present in the body, cystine crystals are deposited in every body structure and lead to the dysfunction of various organ systems in the course of time. Cystine crystals deposited in the cornea are a clinical hallmark of the disease, while there is less awareness of concomitant posterior segment alterations. Symmetrical pigment epithelial mottling and patches of depigmentation frequently start in the periphery and progress towards the posterior pole and can be encountered upon fundus biomicroscopy. Spectral-domain optical coherence tomography (SD-OCT) is an elegant tool for visualizing chorioretinal cystine crystals at the posterior pole. An SD-OCT-based clinical grading of the severity of the chorioretinal manifestation can potentially be applied as a biomarker for systemic disease status and for monitoring oral therapy adherence in the future. Along with previous histological examinations, it may also give information about the location of cystine crystals in the choroid and retina. This review aims to increase the awareness of vision-threatening retinal and choroidal changes in cystinosis and the concomitant findings in SD-OCT.

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.

Neuropsychological and neuroanatomical phenotype in 17 patients with cystinosis

Background

Cystinosis is a rare autosomal recessive disorder caused by intracellular cystine accumulation. Proximal tubulopathy (Fanconi syndrome) is one of the first signs, leading to end-stage renal disease between the age of 12 and 16. Other symptoms occur later and encompass endocrinopathies, distal myopathy and deterioration of the central nervous system. Treatment with cysteamine if started early can delay the progression of the disease. Little is known about the neurological impairment which occurs later. The goal of the present study was to find a possible neuroanatomical dysmorphic pattern that could help to explain the cognitive profile of cystinosis patients. We also performed a detailed review of the literature on neurocognitive complications associated with cystinosis.

Methods

17 patients (mean age = 17.6 years, [5.4–33.3]) with cystinosis were included in the study. Neuropsychological assessment was performed including intelligence (Intelligence Quotient (IQ) with Wechsler’s scale), memory (Children Memory Scale and Wechsler Memory Scale), visuo-spatial (Rey’s figure test) and visuo-perceptual skills assessments. Structural brain MRI (3 T) was also performed in 16 out of 17 patients, with high resolution 3D T1-weighted, 3D FLAIR and spectroscopy sequences.

Results

Intellectual efficiency was normal in patients with cystinosis (mean Total IQ = 93). However the Perceptual Reasoning Index (mean = 87, [63–109]) was significantly lower than the Verbal Comprehension Index (mean = 100, [59–138], p = 0.003). Memory assessment showed no difference between visual and verbal memory. But the working memory was significantly impaired in comparison with the general memory skills (p = 0.003). Visuospatial skills assessment revealed copy and reproduction scores below the 50th percentile rank in more than 70% of the patients. Brain MRI showed cortical and sub-cortical cerebral atrophy, especially in the parieto-occipital region and FLAIR hypersignals in parietal, occipital and brain stem/cerebellum. Patients with atrophic brain had lower Total IQ scores compared to non-atrophic cystinosis patients.

Conclusions

Patients with cystinosis have a specific neuropsychological and neuroanatomical profile. We suggest performing a systematic neuropsychological assessment in such children aiming at considering adequate management.

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.