Ocular involvement in primary hyperoxaluria

Reduced Electroretinogram Responses in Morphologically Normal Retina in Patients with Primary Hyperoxaluria Type 1

Purpose

To describe ocular findings in individuals with primary hyperoxaluria type 1 (PH1), focusing on the correlations between retinal anatomy and retinal function. To characterize the retinal alterations that occur at different disease stages by evaluating individuals with diverse degrees of renal impairment associated with PH1.

Design

A cross-sectional study.

Participants

Patients diagnosed with PH1 based on clinical criteria and genetic testing, treated in the Pediatric Nephrology Unit of the Ruth Children's Hospital, Rambam Health Care Campus, Haifa, Israel between 2013 and 2021.

Methods

The ophthalmological assessment included a slit-lamp biomicroscopy of the anterior and posterior segment or indirect ophthalmoscopy. Electroretinography was employed for assessment of the retinal function, and retinal imaging included spectral-domain OCT and fundus autofluorescence. A systematic evaluation of the disease stage was based on clinical criteria including physical examination, purposeful imaging (X-ray, echocardiography, and US abdomen), and laboratory tests as needed.

Main Outcome Measures

Anatomical and functional assessment of the retina in patients with PH1, and the relationship between retinal dysfunction and kidney impairment.

Results

A total of 16 eyes were examined in the study of 8 children ranging in age from 4 to 19 years. Four eyes (25%) showed normal structural and functional retinal findings, 8 eyes (50%) presented functional impairment in the absence of pathological structural findings, and 4 eyes (25%) had advanced retinal damage that manifested as significant morphological and functional impairment. There was no direct relationship between the severity of the renal disease and the severity of the retinal phenotype.

Conclusions

Subjects with PH1 present varying severity levels of the retinal phenotype, with possible discrepancy between the clinical retinal morphology and the retinal function noted on electroretinography. These findings raise questions about the molecular basis of the retinal manifestations in PH1. The presence of functional impairment in the absence of evident crystal deposition in the retina suggests that, in addition to oxalate crystal accumulation, other biomolecular processes may play a role in the development of retinopathy.

Multimodal Imaging of Severe Oxalate Retinopathy in a 20-Month-Old Boy

Primary hyperoxaluria type 1 (PH1) is a rare disease due to alanine glyoxylate aminotransferase enzyme deficiency caused by mutations in AGXT gene. Increased oxalate causes crystalline deposits in the eye particularly in conjunctiva, cornea, iris, retina, and choroid. A 20-month-old boy was referred with a diagnosis of infantile PH1. There were numerous yellowish crystalline deposits at the posterior pole and hyperpigmented lesions were detected around the macula. Enhanced depth imaging optical coherence tomography (EDI-OCT) revealed dome-shaped retinal pigment epithelium elevations, subretinal and intraretinal hyperreflective material and also choroidal hyperreflective lesions. To the best of our knowledge, this is the first case to document choroidal deposition by EDI-OCT at such an early period of life. [Ophthalmic Surg Lasers Imaging Retina 2022;53:697-700.].

Long-term complications of systemic oxalosis in children-a retrospective single-center cohort study

BACKGROUND

Systemic oxalosis is a severe complication seen in primary hyperoxaluria type I patients with kidney failure. Deposition of insoluble calcium oxalate crystals in multiple organs leads to significant morbidity and mortality.

METHODS

We describe a retrospective cohort of 11 patients with systemic oxalosis treated at our dialysis unit from 1982 to 1998 (group 1) and 2007-2019 (group 2). Clinical and demographic data were collected from medical records. Imaging studies were only available for patients in group 2 (n = 5).

RESULTS

Median age at dialysis initiation was 6.1 months (IQR 4-21.6), 64% were male. Dialysis modality was mostly peritoneal dialysis in group 1 and daily hemodialysis in group 2. Bone disease was the first manifestation of systemic oxalosis, starting with the appearance of sclerotic bands (mean 166 days, range 1-235), followed by pathological fractures in long bones (mean 200.4 days, range 173-235 days). Advanced disease was characterized by vertebral fractures with resulting kyphosis, worsening splenomegaly, and adynamic bone disease. Two patients developed pulmonary hypertension, 4 and 8 months prior to their death. Four of 11 patients developed hypothyroidism 0-60 months after dialysis initiation. Only one patient survived after a successful liver-kidney transplantation. Four patients died after liver or liver-kidney transplantation.

CONCLUSIONS

This is the first comprehensive description of the natural history of pediatric systemic oxalosis. We hope that our findings will provide basis for a quantitative severity score in future, larger studies.

Choroidal neovascularization in a child with infantile primary hyperoxaluria treated with bevacizumab

Fundus manifestations of primary hyperoxaluria include crystalline deposits, focal or diffuse macular hyperpigmentation, and subretinal fibrosis. Choroidal neovascularization has been hypothesized to underlie the pathogenesis of subretinal fibrosis, yet its manifestations are rarely observed. We report a case of infantile primary hyperoxaluria type 1 in a 17-month-old infant with macular subretinal fluid and subretinal hemorrhage that was associated with leakage on fluorescein angiography and responded to bevacizumab treatment, consistent with choroidal neovascularization. This case suggests that choroidal neovascularization may contribute to subretinal fibrosis and subsequent vision loss in infantile primary hyperoxaluria and may benefit from anti-vascular endothelial growth factor therapy.

Oxalate retinopathy is irreversible despite early combined liver-kidney transplantation in primary hyperoxaluria type 1

In primary hyperoxaluria type 1 (PH1), systemic oxalate deposition (oxalosis) in end-stage renal disease (ESRD) is associated with high morbidity and mortality, particularly in children with infantile oxalosis (IO). Combined liver and kidney transplantation (CLKT) is the only curative treatment option in these patients. After CLKT, systemic oxalosis decreases continuously, although only insufficient data are available regarding oxalate retinopathy (ROx), leading to severe visual impairment. We analyzed long-term follow-up data of ROx in 13 patients undergoing CLKT for PH1 at our center between 1998 and 2018. Age at transplantation was 1.3-14.2 years, including nine patients with IO. We performed visual acuity testing, slit lamp investigation, funduscopy, fundus photography, and spectral-domain optical coherence tomography (SD-OCT) imaging. Severe (grade 2-4) ROx was present in all nine children with IO but not in the four patients developing ESRD in adolescence. A significant negative correlation was found between age at onset of ESRD and grade of ROx (r = -0.66; P < .001). Notably, follow-up assessment after CLKT demonstrated no regression of ROx after a median of 5.3 years (range 0.6-14). The data show that despite early CLKT in IO, ROx is irreversible and the concomitant visual deterioration occurs prior to transplantation.

The Ocular Phenotype in Primary Hyperoxaluria Type 1

PURPOSE

To investigate ophthalmic features in a large group of patients with primary hyperoxaluria type 1 (PH1) and to determine the relation between ocular involvement and systemic disease severity.

DESIGN

Retrospective, cross-sectional, multicenter study of the OxalEurope Registry Network.

METHODS

Sixty-eight patients with PH1 were included. Infantile PH1 was diagnosed in 12 patients, and non-infantile PH1 was diagnosed in 56 patients (17 with end-stage renal disease). Ophthalmic examination included best corrected visual acuity (BCVA) testing and multimodal retinal imaging, including fundus photography and optical coherence tomography (OCT). In selected cases, fundus autofluorescence imaging was performed.

RESULTS

All eyes (n = 24) of infantile PH1 patients revealed severe retinal alterations and oxalate deposits, including macular crystals and hyperpigmentations (n = 9, 38%), and subretinal fibrosis (n = 15, 63%) with (n = 7, 47%) or without (n = 8; 53%) associated chronic retinal edema. In 9 eyes (38%, all with subretinal fibrosis), BCVA was significantly reduced (<20/50 Snellen equivalent). In contrast, all eyes (n = 112) of patients with non-infantile PH1 had a BCVA in the normal range (median, 20/20). Only 6 patients with non-infantile disease (11%, all with end-stage renal disease) showed mild, likely PH1-related retinal features. These deposits appeared as focal hyperreflective subretinal lesions on OCT imaging and were hyperautofluorescent on autofluorescence images.

CONCLUSIONS

Severe ocular alterations occur in infantile cases, whereas mild or no ocular alterations are typical in non-infantile PH1 patients. The natural history of (sub)retinal oxalate deposits, the pathogenesis of subretinal fibrosis, and exact factors influencing the overall severity of ocular disease manifestation remain to be determined.

DETAILED CLINICAL PHENOTYPING OF OXALATE MACULOPATHY IN PRIMARY HYPEROXALURIA TYPE 1 AND REVIEW OF THE LITERATURE

PURPOSE

To describe the structural and functional characteristics of oxalate retinopathy.

METHODS

Five patients with molecularly confirmed primary hyperoxaluria (PH) Type 1 underwent multimodal retinal imaging (spectral-domain optical coherence tomography, white light, and HRA multispectral imaging) and functional testing, including color vision testing, Goldmann perimetry, and International Society for Clinical Electrophysiology of Vision standard electrophysiological testing.

RESULTS

Four distinct retinal phenotypes are presented. One patient with a c.[33dupC]; c.[731T>C] mutation showed bilateral perifoveal retinal pigment epithelium hyperplasia. The fundus in the four other patients, all of whom share an identical homozygous c.[33dupC] mutation, ranged from normal to bilateral widespread distribution of retinal crystals and confluent macular retinal pigment epithelium hyperplasia with subfoveal fibrosis. All patients who had developed end-stage renal disease showed some sign of retinopathy, more severe with earlier onset.

CONCLUSION

Retinopathy in PH Type 1 shows considerable interindividual variation. No correlation between genotype and retinal phenotype was detected. Oxalate crystals at the level of the retinal pigment epithelium seem to be irreversible. A proposed clinical grading system of oxalate maculopathy, based on a literature review, may provide clinicians with a tool to better predict visual function and prognosis.

Primary hyperoxalurias: diagnosis and treatment

Primary hyperoxalurias (PH) comprise a group of three distinct metabolic diseases caused by derangement of glyoxylate metabolism in the liver. Recent years have seen advances in several aspects of PH research. This paper reviews current knowledge of the genetic and biochemical basis of PH, the specific epidemiology and clinical presentation of each type, and therapeutic approaches in different disease stages. Potential future specific therapies are discussed.

Enhanced depth imaging optical coherence tomography features in a young case of primary hyperoxaluria Type 1

PURPOSE

To describe the enhanced depth imaging optical coherence tomography findings in a very young case of Type 1 primary hyperoxaluria.

METHODS

Observational case report of a young patient who underwent clinical examination and enhanced depth imaging optical coherence tomography evaluation.

RESULTS

A 4-year-old boy with a history of Type 1 primary hyperoxaluria and resulting chronic renal failure was referred to us for ophthalmologic examination. There were no ocular symptoms when he was referred to us. Fundus examination showed deposition of calcium oxalate crystals at the posterior pole located symmetrically in both eyes. Enhanced depth imaging optical coherence tomography evaluation revealed hyperreflective structures, localized under the photoreceptor inner segment/outer segment junction, and over the retinal pigment epithelium, consistent with deposition of oxalate crystals. There were no oxalate crystals in the superficial retinal layers, and we observed no evidence of deposition of oxalate crystals in choroid with enhanced depth imaging optical coherence tomography.

CONCLUSION

We could not demonstrate any oxalate deposits in the choroid with enhanced depth imaging optical coherence tomography in this young case of primary hyperoxaluria Type 1. This may be related to the young age of our patient, and the amounts of the crystalline deposition may increase in the years ahead.

Crystalline Retinopathies

Many types of crystalline retinopathies have been described, associated with a myriad of medical conditions ranging from chronic retinal conditions to inherited systemic diseases. This comprehensive review summarizes the different types of crystalline retinopathies, including their clinical presentations, diagnostic criteria, pathology, and treatment options.

Natural history of acquired retinal oxalosis in a child

We report the natural history of acquired retinal oxalosis in a child with chronic renal failure. The clinical manifestations were characterized by a transient crystalline retinopathy, but stable, diffuse, flecked retina-like changes and focal hypertropic retinal pigment epithelial lesions. The pathophysiology and previous reports of retinal oxalosis are reviewed.

West African crystalline maculopathy

OBJECTIVE

To report new observations in West African crystalline maculopathy.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Three patients drawn from a private retina practice.

METHODS

Review of clinical charts and photographic studies.

MAIN OUTCOME MEASURES

Distribution of intraretinal crystals and changes after laser photocoagulation, and history of ingesting foods typical in a West African diet but atypical for an American diet.

RESULTS

All patients were older than 50 years, had diabetic retinopathy, ate green vegetables not found in American diets, and showed no deleterious effects of the crystals. Kola nut ingestion in 2 patients was remote and sparse, and was unknown in a third patient. The first 2 affected patients originating outside the Ibo tribe of Nigeria are reported. The pattern of retinal crystals can be changed, and the quantity of crystals reduced, by laser photocoagulation of associated diabetic retinopathy.

CONCLUSIONS

West African crystalline retinopathy is distinguishable from other causes of crystalline retinopathy. It may reflect a component of the West African diet, seems to have diabetic retinopathy as a promoting factor via breakdown of the blood-retina barrier, and can be modified by laser photocoagulation of diabetic retinopathy. Increased awareness of the condition will allow physicians seeing West African immigrants to make the diagnosis and treat the patients appropriately.

Choroidal neovascularization in primary hyperoxaluria

PURPOSE

To report a case of primary hyperoxaluria in which choroidal neovascularization developed bilaterally.

DESIGN

Observational case report.

METHODS

A 22-year-old man with a history of type I primary hyperoxaluria complained of a slow but progressive loss of vision in both eyes for the preceding 8 months. The clinical, fluorescein, and ocular coherence tomography findings are reported.

RESULTS

Fluorescein angiography confirmed the presence of choroidal neovascularization in both eyes at the edge of previous macular scars. Ocular coherence tomography scans were obtained to better characterize the clinical pathology.

CONCLUSION

In a patient with type 1 primary hyperoxaluria, the presence of choroidal neovascularization in both eyes outside but adjacent to an area of previous macular scarring is reported. These findings are in harmony with the assumption that mechanical factors from the oxalate deposition promote choroidal neovascularization.

Histological study of oxalosis in the eye and adnexa of AIDS patients

Review of a series of 98 eyes removed at autopsy from 86 AIDS patients identified 12 cases (14%) showing varying degrees of microscopic calcium oxalate deposition. The oxalate crystals were birefringent using polarisation microscopy and were stained histochemically by the silver nitrate-rubeanic acid method (Yasue), a stain considered to be specific for calcium oxalate. In two cases, the deposition was extensive and involved the surface of the ciliary processes, ciliary body and pars plana of the retina, the retinal and optic nerve blood vessel wall, a few retinal pigment cells, and the anterior inner sclera. A lesser degree of intraocular involvement was observed in the remaining 10 cases. In all but two eyes, where a peripheral active area of cytomegalovirus retinitis was present, no other significant microscopical abnormality was found. Clinically, these patients were asymptomatic. At autopsy, oxalate deposits were found in the kidney and/or thyroid in seven of the patients.

A clinicopathological study of ocular involvement in primary hyperoxaluria type I

We performed a clinicopathological study on the eyes of a 3-year-old girl with primary hyperoxaluria type I. An examination one year before death disclosed a slightly diminished visual acuity in both eyes with black, geographic central macular, subretinal patches. Calcium oxalate was deposited predominantly in the retinal pigment epithelium of the posterior pole, where these cells were markedly hyperplastic and hypertrophied round foci of oxalate crystals. Oxalate crystals were exceedingly sparse in other ocular structures and when present were not associated with an apparent tissue reaction in these other locations. A collagenous layer was evident between parts of the retinal pigment epithelium and the neurosensory retina, which contained occasional perivascular clumps of melanin laden cells. The predominant deposition of oxalate in the retinal pigment epithelium, with the exuberant response of these cells around the crystals, gives a clue to the pathogenic mechanisms of primary hyperoxaluria.

The peroxisome and the eye

Several childhood multisystem disorders with prominent ophthalmological manifestations have been ascribed to the malfunction of the peroxisome, a subcellular organelle. The peroxisomal disorders have been divided into three groups: 1) those that result from defective biogenesis of the peroxisome (Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum's disease); 2) those that result from multiple enzyme deficiencies (rhizomelic chondrodysplasia punctata); and 3) those that result from a single enzyme deficiency (X-linked adrenoleukodystrophy, primary hyperoxaluria type 1). Zellweger syndrome, the most lethal of the three peroxisomal biogenesis disorders, causes infantile hypotonia, seizures, and death within the first year. Ophthalmic manifestations include corneal opacification, cataract, glaucoma, pigmentary retinopathy and optic atrophy. Neonatal adrenoleukodystrophy and infantile Refsum's disease appear to be genetically distinct, but clinically, biochemically, and pathologically similar to Zellweger syndrome, although milder. Rhizomelic chondrodysplasia punctata, a peroxisomal disorder which results from at least two peroxisomal enzyme deficiencies, presents at birth with skeletal abnormalities and patients rarely survive past one year of age. The most prominent ocular manifestation consists of bilateral cataracts. X-linked (childhood) adrenoleukodystrophy, results from a deficiency of a single peroxisomal enzyme, presents in the latter part of the first decade with behavioral, cognitive and visual deterioration. The vision loss results from demyelination of the entire visual pathway, but the outer retina is spared. Primary hyperoxaluria type 1 manifests parafoveal subretinal pigment proliferation. Classical Refsum's disease may also be a peroxisomal disorder, but definitive evidence is lacking. Early identification of these disorders, which may depend on recognizing the ophthalmological findings, is critical for prenatal diagnosis, treatment, and genetic counselling.

Corneal and conjunctival crystals in paraproteinemia

A 64-year-old woman with bilateral corneal and conjunctival crystal deposition was evaluated. A biopsy of her conjunctiva showed intracytoplasmic inclusions of immunoglobulin crystals in fibrocytes, macrophages, and endothelial cells. Serum protein electrophoresis showed elevated kappa and IgA light and heavy chains which corresponded with immunoperoxidase staining results of the conjunctival biopsy. Conjunctival and corneal crystal deposition may be indicative of paraproteinemia, and histopathologic examination of a conjunctival biopsy may be useful in diagnosing this condition.

Early onset of stone diseases and primary hyperoxaluria

A case of primary hyperoxaluria is presented. In a product of consanguinous marriage recurrent stone formation, nephrocalcinosis and increased urinary oxalate excretion revealed the diagnosis of hyperoxaluria. Diagnosis and treatment of primary hyperoxaluria are briefly reviewed and the importance of elevated urinary oxalate level in diagnosis is emphasized.

[Type I oxalosis in childhood--studies within the scope of terminal renal failure in the child]

The difficulties of biochemical diagnosis in children and in chronic renal failure are discussed in detail, as well as the development of diagnostic and therapeutic possibilities in recent years, exemplified by 4 cases. Excretion of oxalate (and glycolate) may be incorrectly assumed to be normal with: a) uncritical application of the method of measurement, b) disregard of the clearly lower oxalate excretion in children (values should be referred to m2 of body surface), c) disregard of a decreased glomerular filtration rate (values should be referred to the creatinine clearance). With compromised renal function the excretion of oxalate and glycolate in primary oxalosis drops to "normal" whereas plasma values increase considerably. In this case the biochemical diagnosis is possible only by measurement of plasma values of glycolate and oxalate. Consequently, extensive extrarenal deposition of calcium oxalate crystals will, as a rule, become clinically manifest only after chronic renal failure has turned irreversible. In recent years, several therapeutic procedures, have been developed. They are of therapeutic significance for the early stages of the disease as well. Observing especially conditions renal transplantation or combined hepatorenal transplantation can be managed with a successful outcome. As the perioxisomal enzyme is activated only in the liver cells, an early liver transplantation as a definitive treatment by enzyme replacement may be the successful therapy in the future.

New aspects of infantile oxalosis

Infantile oxalosis is the most severe form of primary hyperoxaluria type I (PH I). Only 28 patients have been reported in detail; it was found that diagnosis was usually delayed, and most patients presented before the age of 4 months in renal failure and died within the 1st year of life. This report comprises two infants in whom diagnosis of PH I was made in the first few weeks of life before renal function was impaired. Case 1, whose brother had died of infantile oxalosis, already had greatly increased urinary oxalate and glycolate excretion at 7 days of age. In Case 2, PH I was diagnosed early because of the finding of increased renal echogenicity at 3 weeks of age; this patient had numerous episodes of stone formation despite continuous treatment with pyridoxine, but maintained renal function with normal serum creatinine levels at the age of 28 months. Prenatal diagnosis was attempted in case 1; however, amniotic fluid oxalate and glycolate concentrations were normal, suggesting that these acids pass the placenta and are not retained. The recent discovery of a transamination defect (deficiency of the peroxisomal enzyme alanine: glyoxylate aminotransferase) explains why some patients respond to pyridoxine treatment. Differences in onset and severity of PH I and in response to pyridoxine suggest that this disorder is biochemically and genetically heterogeneous.