A comprehensive monocentric ophthalmic study with Gaucher disease type 3 patients: vitreoretinal lesions, retinal atrophy and characterization of abnormal saccades

A review of type 3 Gaucher disease: unique neurological manifestations and advances in treatment

Gaucher disease (GD) is a rare lysosomal storage disease that is caused by mutations in the GBA gene. It is classified into three main phenotypes according to the patient's clinical presentation. Of these, chronic neuronopathic GD (GD3) is characterized by progressive neurological damage. Understanding the unique neurological manifestations of GD3 has important diagnostic and therapeutic implications. Our article summarizes the neurological symptoms specific to GD3 and related therapeutic advances, and it highlights the relevance of the gene to clinical symptoms, so as to provide a reference for the diagnosis and treatment of GD3.

Repetitive, non-invasive imaging of neurodegeneration, and prevention of it with gene replacement, in mice with Sanfilippo syndrome

Hampering assessment of treatment outcomes in gene therapy and other clinical trials in patients with childhood dementia is the lack of an objective, non-invasive measure of neurodegeneration. Optical coherence tomography (OCT) is a widely available, rapid, non-invasive, and quantitative method for examining the integrity of the neuroretina. Profound brain and retinal dysfunction occur in patients and animal models of childhood dementia, including Sanfilippo syndrome and we recently revealed a correlation between the age of onset and rate of progression of retinal and brain degeneration in sulfamidase-deficient Sanfilippo mice. The aim of the current study was to use OCT to visualise the discrete changes in retinal structure that occur during disease progression. A progressive decline in retinal thickness was readily observable in Sanfilippo mice using OCT, with differences seen in affected animals from 10-weeks of age. OCT applied to i.v. AAV9-sulfamidase-treated Sanfilippo mice enabled visualisation of improved retinal anatomy in living animals, an outcome confirmed via histology. Importantly, brain disease lesions were also ameliorated in treated Sanfilippo mice. The findings highlight the sensitivity, ease of repetitive use and quantitative capacity of OCT for detection of discrete changes in retinal structure and their prevention with a therapeutic. Combined with the knowledge that retinal and brain degeneration are correlated in Sanfilippo syndrome, OCT provides a window to the brain in this and potentially other childhood dementias.

Role of TFEB in Diseases Associated with Lysosomal Dysfunction

Transcription factor EB (TFEB) plays a very important role in the maintenance of cellular homeostasis. TFEB is a transcription factor that regulates the expression of several genes in the Coordinated Lysosomal Expression and Regulation (CLEAR) network. The CLEAR network genes are known to regulate many processes associated with the autophagy pathway and lysosome biogenesis. Lysosomes, which are degradative organelles in the cell, are associated with several cellular mechanisms, such as autophagy and phagocytosis. Recent studies have shown that TFEB dysregulation and lysosomal dysfunction are associated with several degenerative diseases. Thus, enhancing TFEB activity and accompanied induction of lysosomal function and autophagy can have tremendous therapeutic potential for the treatment of several degenerative diseases including age-related macular degeneration (AMD). In this chapter, we briefly illustrate the expression and regulation of TFEB in response to several cellular stressors and discuss the effects of TFEB overexpression to induce cellular clearance functions.

Autophagy in the retinal pigment epithelium: a new vision and future challenges

The retinal pigment epithelium (RPE) is a highly specialized monolayer of polarized, pigmented epithelial cells that resides between the vessels of the choriocapillaris and the neural retina. The RPE is essential for the maintenance and survival of overlying light-sensitive photoreceptors, as it participates in the formation of the outer blood-retinal barrier, phagocytosis, degradation of photoreceptor outer segment (POS) tips, maintenance of the retinoid cycle, and protection against light and oxidative stress. Autophagy is an evolutionarily conserved 'self-eating' process, designed to maintain cellular homeostasis. The daily autophagy demands in the RPE require precise gene regulation for the digestion and recycling of intracellular and POS components in lysosomes in response to light and stress conditions. In this review, we discuss selective autophagy and focus on the recent advances in our understanding of the mechanism of cell clearance in the RPE for visual function. Understanding how this catabolic process is regulated by both transcriptional and post-transcriptional mechanisms in the RPE will promote the recognition of pathological pathways in genetic disease and shed light on potential therapeutic strategies to treat visual impairments in patients with retinal disorders associated with lysosomal dysfunction.

Hydroxychloroquine Causes Early Inner Retinal Toxicity and Affects Autophagosome-Lysosomal Pathway and Sphingolipid Metabolism in the Retina

Hydroxychloroquine (HCQ) is an anti-malarial drug but also widely used to treat autoimmune diseases like arthritis and lupus. Although there have been multiple reports of the adverse effect of prolonged HCQ usage on the outer retina, leading to bull's-eye maculopathy, the effect of HCQ toxicity on the inner retina as well as on overall visual functions has not been explored in detail. Furthermore, lack of an established animal model of HCQ toxicity hinders our understanding of the underlying molecular mechanisms. Here, using a small clinical study, we confirmed the effect of HCQ toxicity on the inner retina, in particular the reduction in central inner retinal thickness, and established a mouse model of chronic HCQ toxicity that recapitulates the effects observed in human retina. Using the mouse model, we demonstrated that chronic HCQ toxicity results in loss of inner retinal neurons and retinal ganglion cells (RGC) and compromises visual functions. We further established that HCQ treatment prevents autophagosome-lysosome fusion and alters the sphingolipid homeostasis in mouse retina. Our results affirm the notion that HCQ treatment causes early damage to the inner retina and affects visual functions before leading to characteristic toxicity in the macular region of the outer retina, 'bull's-eye maculopathy.' We also provide insights into the underlying molecular mechanisms of HCQ retinal toxicity that may involve autophagy-lysosomal defects and alterations in sphingolipid metabolism.

Retinal thinning in phenylketonuria and Gaucher disease type 3

PURPOSE

Retinal alterations in inherited metabolic diseases associated with neurodegeneration are poorly studied. The objective was to study retinal thickness, specifically the components of the ganglion cell complex (GCC)-nerve fiber layer (NFL), ganglion cell layer (GCL), and inner plexiform layer (IPL)-using spectral-domain optical coherence tomography (SD-OCT) in two different diseases with potential dopaminergic depletion, phenylketonuria (PKU) and Gaucher disease type 3 (GD3).

METHODS

Retinal layers in 19 patients with PKU, 15 patients with GD3, and 93 healthy individuals were measured using peripapillary ring scan and macular SD-OCT. Linear mixed models were computed including an adjustment for age, sex, and spherical equivalent. We calculated Spearman's rank correlations between retinal layer measurements and clinical and/or laboratory parameters.

RESULTS

Thinning of total retinal thickness was found in the macular inner ring (p = 0.002), and outer ring (p = 0.012), sparing the fovea (p = 0.12) in PKU, while in GD3, all subfields were thinned (fovea p < 0.001, inner ring p = 0.047, outer ring 0.07). In both conditions, thinning was most evident in the NFL, GCL, and IPL, while OPL (outer plexiform layer) was thickened. Peripapillary retinal nerve fiber layer measurements remained normal. GCL and IPL in PKU correlated with tyrosine serum concentration.

CONCLUSION

Thinning of the NFL, GCL, and IPL, with thickened OPL, are both found in PKU and in GD3. Low dopamine concentrations in the retina might promote these effects. However, these data do not give evidence that retinal measurements can be used as a biomarker for disease severity in patients with GD3.

Eye motor manifestations in children with neurometabolic disorders

Neurometabolic diseases are complex group of rare neurogenetic disorders, which are difficult to diagnose. Patients may have toxic metabolite accumulation, inadequate energy supply, or neurotransmitter deficiency, resulting in a variety of clinical manifestations and severity with enzyme activity or transporter function defects. Multiple organ involvement is frequently seen, among which neurological symptoms and signs are one of the most encountered problems. Ocular motor problems deserve special attention for it occurs in some inborn error of metabolism. Furthermore, some are early signs or characteristic findings of certain diseases, such as the gaze palsy in Niemann-Pick disease type C and Gaucher disease or oculogyric crisis in neurotransmitter diseases. Early recognition and intervention are important for better prognosis in treatable neurometabolic disorders. In addition, ways to evaluate and describe eye movement problems also help to demonstrate the severity or clinical progression for those diagnosed with certain neurometabolic diseases. However, the complexity of eye movement and ocular motor control renders our clinical observation, recording and even anatomic localization of abnormal eye movements. Clinicians are more likely to detect early signs and unravel problems by gaining awareness of abnormal eye movement. This study amied to approach neurometabolic diseases in children via eye motor manifestations.

Throwing a spotlight on under-recognized manifestations of Gaucher disease: Pulmonary involvement, lymphadenopathy and Gaucheroma

BACKGROUND

Gaucher disease (GD) is a rare lysosomal storage disorder classically subdivided into type 1 (non-neuronopathic) GD, and types 2 and 3 (neuronopathic) GD. It is typically characterized by clinical manifestations including anemia, thrombocytopenia, hepatosplenomegaly, bone lesions, and (in more severe forms) neurological impairment. However, less-commonly reported and often under-recognized manifestations exist, which potentially have a significant impact on patient outcomes. Greater efforts are needed to understand, recognize, and manage these manifestations.

OBJECTIVES

This review provides a synthesis of published information about three under-recognized GD manifestations (pulmonary involvement, lymphadenopathy, and Gaucheroma) and recommends diagnostic, management, and treatment strategies based on the available literature and author experience. The authors aim to raise awareness about these serious, progressive, and sometimes life-threatening conditions, which are often diagnosed late in life.

CONCLUSIONS

Little is known about the incidence, pathophysiology, prognostic factors, and optimal management of pulmonary involvement, lymphadenopathy, and Gaucheroma in patients with GD. Enzyme replacement therapy (ERT) has shown limited efficacy for the prevention and treatment of these manifestations. More research is needed to evaluate the potential effect of substrate reduction therapy (SRT) with glucosylceramide synthase (GCS) inhibitors, and to develop additional approaches to treat these GD manifestations. Improvements in data collection registries and international data-sharing are required to better understand the impact of these manifestations on GD patients, help develop effective management strategies, and, ultimately, improve patient outcomes.

Vertical saccadic palsy and foveal retinal thinning in Niemann-Pick disease type C

INTRODUCTION

Niemann-Pick type C (NPC) is a lysosomal storage disease that is progressive and life-limiting, with an estimated incidence of 1:120,000 live births. In addition to systemic manifestation with (hepato-)splenomegaly, there are a number of neurological manifestations (ataxia, dysarthria, dementia, cataplexy, epileptic seizures, and psychiatric disorders). Characteristic is vertical supranuclear gaze palsy, which is often overlooked. Early diagnosis and start of therapy improve quality of life. This study aimed to characterize oculomotor dysfunction of NPC patients, and to provide ophthalmologic data including retinal imaging.

METHODS

Eighteen patients with biochemically or genetically diagnosed NPC completed oculomotor and ophthalmologic examination. Ten of them performed saccadometry by infrared based video-oculography. Saccadic parameters were compared to 100 healthy controls, and were correlated with clinical variables. Another subgroup of eight patients received optical coherence tomography (OCT) of the optic disc and the macula, of which the segmented layers were analysed using a crude linear mixed model, and one adjusted for age, sex, and spherical equivalent.

RESULTS

Saccadometry revealed slowed peak velocity compared to controls most evident vertically. Peak velocity correlated negatively with SARA-Score, but correlation with clinical assessment of saccades was not significant. Clinical features in the assessment of vertical saccades were intensive blinking and head movements to initiate gaze changes, and lateral trajectory of the eyes. Macular OCT revealed significant total retinal thinning in the fovea, specifically of the outer nuclear layer and outer retinal layer. Para- and perifoveal retinal thicknesses, as well as peripapillary retinal nerve fibre layer were normal.

CONCLUSIONS

Foveal thinning was revealed in NPC. It remains to be shown, whether OCT will prove to be useful to monitor progression. Saccadic impairment reflects CNS involvement and therefore is a parameter to demonstrate the progression of NPC, and potentially also the efficacy of new therapies. Saccadometry, in contrast to clinical investigation, allows the precise evaluation of saccades.

Eye movement biomarkers allow for the definition of phenotypes in Gaucher Disease

BACKGROUND

Neurological forms of Gaucher disease, the inherited disorder of β-Glucosylceramidase caused by bi-allelic variants in GBA1, is a progressive disorder which lacks a disease-modifying therapy. Systemic manifestations of disease are effectively treated with enzyme replacement therapy, however, molecules which cross the blood-brain barrier are still under investigation. Clinical trials of such therapeutics require robust, reproducible clinical endpoints to demonstrate efficacy and clear phenotypic definitions to identify suitable patients for inclusion in trials. The single consistent clinical feature in all patients with neuronopathic disease is the presence of a supranuclear saccadic gaze palsy, in the presence of Gaucher disease this finding serves as diagnostic of 'type 3' Gaucher disease.

METHODS

We undertook a study to evaluate saccadic eye movements in Gaucher patients and to assess the role of the EyeSeeCam in measuring saccades. The EyeSeeCam is a video-oculography device which was used to run a protocol of saccade measures. We studied 39 patients with non-neurological Gaucher disease (type 1), 21 patients with type 3 (neurological) disease and a series of 35 healthy controls. Mean saccade parameters were compared across disease subgroups.

RESULTS

We confirmed the saccadic abnormality in patients with type 3 Gaucher disease and identified an unexpected subgroup of patients with type 1 Gaucher disease who demonstrated significant saccade parameter abnormalities. These patients also showed subtle neurological findings and shared a GBA1 variant.

CONCLUSIONS

This striking novel finding of a potentially attenuated type 3 Gaucher phenotype associated with a specific GBA1 variant and detectable saccadic abnormality prompts review of current disease classification. Further, this finding highlights the broad spectrum of neuronopathic Gaucher phenotypes relevant when designing inclusion criteria for clinical trials.

Vitreous Hemorrhage in Type 3 Gaucher Disease: An Angiographic and Pathologic Analysis

PURPOSE

To describe the case of a 12-year-old female with vitreoretinal manifestations of Type 3 Gaucher disease.

METHODS

Retrospective case report including multimodal imaging and histologic examination of the vitreous.

RESULTS

A 12-year-old female with a history of Gaucher disease Type 3 was referred to the ophthalmology service for evaluation of vitreous deposits in both eyes. Funduscopic examination was notable for white vitreous opacities in both eyes. Ultra-widefield fluorescein angiography demonstrated areas of blockage associated with the deposits as well as focal areas of leakage. OCT angiography showed shadow artifact without intrinsic flow at these sites. Three years after presentation, she developed a right hemorrhagic posterior vitreous detachment, requiring pars plana vitrectomy with scleral buckle. A vitreous sample was sent to pathology, which demonstrated Gaucher cells.

DISCUSSION

Gaucher disease is a rare metabolic condition caused by an autosomal recessive deficiency of glucocerebrosidase. To our knowledge, this is the first report of hemorrhagic posterior vitreous detachment in Type 3 Gaucher disease, including ultra-widefield imaging, OCT angiography, and histopathology.

The definition of neuronopathic Gaucher disease

Neuronopathic Gaucher disease (nGD) has a very wide clinical and genotypic spectrum. However, there is no consensus definition of nGD, including no description of how best to diagnostically separate the acute form-Gaucher type 2-from the subacute or chronic form-Gaucher type 3. In this article, we define the various forms of Gaucher disease with particular emphasis on the presence of gaze palsy in all patients with nGD. This consensus definition will help in both clinical diagnosis and appropriate patient recruitment to upcoming clinical trials.

Saccadic reaction time and ocular findings in phenylketonuria

Background

Phenylketonuria (PKU) is an inherited metabolic disorder characterized by reduced activity of phenylalanine hydroxylase resulting in elevated blood phenylalanine (Phe) concentration. Despite some obvious ocular changes, the disorder has been poorly recognized by ophthalmologists. Neurophysiologic tests imply prolonged reaction time correlating with increased phenylalanine blood concentrations. We aimed to test saccadic reaction time in PKU patients in dependency of blood phenylalanine concentrations.

Methods

Nineteen biochemically diagnosed PKU patients and 100 controls completed comprehensive ophthalmologic and orthoptic examinations including saccadometry by infrared based video-oculography. Peak velocity, gain, and particularly latency of reflexive saccades were compared to controls, and regression analysis was performed.

Results

Latency of reflexive saccades was not associated with the current phenylalanine concentration. Although in 10 out of 19 patients phenylalanine concentrations were outside the age-related therapeutic range, latency differed little between PKU patients and the controls, as well as peak velocity and gain. Ocular findings occurred as partial hypopigmentation of the iris in one late diagnosed patient aged 36 years, and as bilateral cataracts (possibly due to steroid intake) with refractive amblyopia, strabismus, high myopia, and glaucoma in another late diagnosed patient aged 46 years. Visual acuity was reduced in eight PKU patients.

Conclusions

Saccadometry, particularly saccadic reaction time, is not useful in the monitoring of phenylketonuria. Ophthalmic examination is recommended in PKU patients, as the occurrence of ocular pathologies was relatively high.