Clinical features and pathogenesis of Alport retinopathy

Ocular Manifestations and Potential Treatments of Alport Syndrome: A Systematic Review

Objectives. Alport syndrome (AS) is a severe, rare hereditary disorder that can lead to end-stage renal disease, auditory degeneration, and ocular abnormalities. Despite extensive research on AS in relation to auditory and renal disorders, more research is needed on the ocular presentations of AS. This systematic review aims to summarize the common ocular abnormalities in patients with AS and to explore the potential treatment options for these irregularities. Methods. The PubMed, MEDLINE, and EMBASE databases were systematically searched from January 1977 to April 2022. Only papers that were published in the English language and explored the ocular abnormalities in AS patients were selected. We manually searched reference lists of included papers for additional studies. Results. A total of 23 articles involving 195 patients were included in this review. The common ocular manifestations in AS patients are lenticonus, macular holes, fleck retinopathy, and thinning of the macula. Although published literature has described the use of cataract surgeries and vitrectomies as standard surgical techniques to alleviate ocular abnormalities in non-AS patients, it must be noted that surgical techniques have not been evaluated in a large research study as a solution for AS abnormalities. Another prospective treatment for AS is gene therapy through the reversion of causative COL4 variants to wild type or exon-skipping therapy for X-linked AS with COL4A5 truncating mutations. Gene therapy, however, remains unable to treat alterations that occur in the fetal and early development phase of the disease. Conclusions. The review found no definitive conclusions regarding the efficacy and safety of surgical techniques and gene therapy in AS patients. Recognition of ocular abnormalities through an ophthalmic examination with an optical coherence tomography (OCT) and slit-lamp examination is critical to the medical field, as ophthalmologists can aid nephrologists and other physicians in diagnosing AS. Early diagnosis and care can minimize the risk of detrimental ocular outcomes, such as blindness and retinal detachment.

Alport's syndrome: A rare clinical presentation with crescents

Alport's syndrome (hereditary nephritis) is a familial disorder, which usually affects young males with clinical presentation of hematuric and glomerular disease. We report a rare case of Alport's syndrome in a 16-year-old male with typical extrarenal manifestations and renal biopsy findings with crescents.

Spectrum of retinal abnormalities in renal transplant patients using chronic low-dose steroids

PURPOSE

To assess the ophthalmological characteristics of asymptomatic patients with a renal transplant on chronic low-dose steroids for at least the last 2 years prior to examination.

METHODS

Cross-sectional study. All patients underwent an extensive ophthalmological examination.

RESULTS

Of the 37 included patients [25 male, 12 female; 59 ± 11 years (range, 38-77 years)] ophthalmological phenotyping revealed abnormalities in 22 patients (59%). Findings characteristic for (subclinical) central serous chorioretinopathy were detected in ten patients (27%), including two patients with serous subretinal fluid in the macula. An epiretinal membrane of the macula was present in six patients (16%). Mean subfoveal choroidal thickness was significantly increased in patients with ophthalmological abnormalities, in comparison with patients without abnormalities.

CONCLUSIONS

Retinal abnormalities are common in the majority of renal transplant patients using chronic low-dose steroids. These retinal changes may be associated with the renal disease and/or the effect of chronic steroid use on the choroid and retina.

En face optical coherence tomography findings in a case of Alport syndrome

Alport syndrome is a rare hereditary disease that is associated with retinal abnormalities such as dot-and-fleck retinopathy and temporal macular thinning. The main pathophysiological process of Alport syndrome is loss of the collagen network in the basement membrane. However, the alterations in each retinal layer have not been fully evaluated. In the case presented here, we evaluated the retina of a patient with Alport syndrome using en face optical coherence tomography (OCT). The findings suggested that the primary alterations occur in the internal limiting membrane and the retinal pigment epithelium basement membrane which is a part of the Bruch's membrane. The adjacent retinal layers are damaged subsequently. In conclusion, en face OCT could be useful in evaluating retinal abnormalities and understanding their underlying pathophysiology in Alport syndrome.

Bull's eye and pigment maculopathy are further retinal manifestations of an abnormal Bruch's membrane in Alport syndrome

BACKGROUND AND OBJECTIVES

The retinal features of Alport syndrome include a central and peripheral fleck retinopathy, temporal retinal thinning, and a macular hole. Here we describe further retinal abnormalities.

METHODS

We identified a case of bull's eye maculopathy 20 years previously in a 68-year-old female, and reviewed archived retinal images from our cohort of X-linked (28 males, 28 females) or autosomal recessive (n = 13) Alport syndrome. All individuals had Alport syndrome confirmed on genetic testing or renal biopsy, were examined by an ophthalmologist, and underwent retinal imaging (KOWA non-mydriatic camera, Japan).

RESULTS

The index case had the p.Q379X variant in COL4A5 and currently had renal impairment, (eGFR = 45 ml/min/1.73 m²), bilateral hearing loss, and central and peripheral retinopathies. Her maculopathy had deteriorated, and she had a bilateral central visual field loss. Optical coherence tomography (Heidelberg Spectralis) demonstrated a disrupted retinal pigment epithelium and retinal atrophy. We identified a further early bull's eye maculopathy (1/69, 1.4%) from a female with autosomal recessive disease and normal renal function. We also noted a subtle pigment maculopathy associated with an abnormal retinal pigment epithelium in 27 (27/69, 39%) subjects with Alport syndrome, in both males (8/28, 29%) and females (13/28, 46%) with X-linked disease, and in autosomal recessive disease (6/13, 38%).

CONCLUSIONS

The bull's eye and pigment maculopathies in Alport syndrome result mainly from the damaged Bruch's membrane and overlying retinal pigment epithelium. Bull's eye maculopathy affects vision and patients should undergo regular monitoring for retinal complications.

Identification of microRNAs and their target genes in Alport syndrome using deep sequencing of iPSCs samples

MicroRNAs (miRNAs) are a class of small RNA molecules that are implicated in post-transcriptional regulation of gene expression during development. The discovery and understanding of miRNAs has revolutionized the traditional view of gene expression. Alport syndrome (AS) is an inherited disorder of type IV collagen, which most commonly leads to glomerulonephritis and kidney failure. Patients with AS inevitably reach end-stage renal disease and require renal replacement therapy, starting in young adulthood. In this study, Solexa sequencing was used to identify and quantitatively profile small RNAs from an AS family. We identified 30 known miRNAs that showed a significant change in expression between two individuals. Nineteen miRNAs were up-regulated and eleven were down-regulated. Forty-nine novel miRNAs showed significantly different levels of expression between two individuals. Gene target predictions for the miRNAs revealed that high ranking target genes were implicated in cell, cell part and cellular process categories. The purine metabolism pathway and mitogen-activated protein kinase (MAPK) signaling pathway were enriched by the largest number of target genes. These results strengthen the notion that miRNAs and their target genes are involved in AS and the data advance our understanding of miRNA function in the pathogenesis of AS.

Ocular manifestations of Alport syndrome

AIM

To analyze the clinical manifestation of Alport syndrome, especially the ocular features.

METHODS

The physical, ophthalmologic and audiologic examination results of thirty-two patients with Alport syndrome were analyzed retrospectively.

RESULTS

Thirty (93.7%) patients had some family history. All patients had renal disease: eighteen (56.3%) patients with chronic renal failure, four (12.5%) patients with renal insufficiency, and the other ten (31.3%) patients with hematuria. Twenty (62.5%) patients had sensorineural deafness. Thirteen (40.6%) patients had ocular deformity, five (15.7%) patients had typical ocular changes: three patients with anterior lenticonus, and two patients with macular flecks.

CONCLUSION

Ocular anomalies are not requisite for the diagnosis of Alport syndrome. But its typical ocular features should be recognized by the ophthalmologists which supports the diagnosis.

Retinal basement membrane abnormalities and the retinopathy of Alport syndrome

PURPOSE

To determine the effects of X-linked and autosomal recessive Alport syndrome on retinal basement membranes and how these result in the characteristic perimacular dot-and-fleck retinopathy, lozenge, and macular hole.

METHODS

The type IV collagen chains present in the normal retina were determined immunohistochemically. Ten patients with Alport syndrome underwent retinal photography and optical coherence tomography to determine the thickness of the internal limiting membrane (ILM) by segmentation analysis, the layers affected by the retinopathy, and any correlates of the lozenge and macular hole. Bruch's membrane was examined directly by electron microscopy in a donated Alport eye.

RESULTS

The alpha3alpha4alpha5 type IV collagen network was present in the normal ILM and in the retinal pigment epithelium basement membrane of Bruch's membrane. In Alport syndrome, the ILM/nerve fiber layer and Bruch's membrane were both thinned. The dot-and-fleck retinopathy corresponded to hyperreflectivity of the ILM/nerve fiber layer in the distribution of the nerve fiber layer. The lozenge and macular hole corresponded to temporal macular thinning. The thinning across the whole retina was principally due to thinning of the ILM/nerve fiber layer and inner nuclear layer.

CONCLUSIONS

The Alport dot-and-fleck retinopathy results primarily from abnormalities in the ILM/nerve fiber layer rather than in Bruch's membrane. Thinning of the ILM/nerve fiber layer contributes to the retinopathy, lozenge, and macular hole, possibly through interfering with nutrition of the overlying retina or clearance of metabolic by-products.

Opinion: Ocular features aid the diagnosis of Alport syndrome

Alport syndrome is a common cause of inherited kidney failure but often goes unrecognized. Most affected families show an X-linked pattern of inheritance where affected males develop renal failure and hearing loss, and often lenticonus and retinopathy. Lenticonus is evident on both ophthalmoscopy and slit-lamp examination but retinal abnormalities are more obvious on imaging. Such abnormalities include a perimacular dot-and-fleck retinopathy and a peripheral fleck retinopathy, which might occur independently of each other; a 'dull macular reflex' or 'lozenge', when the perimacular flecks are confluent; and, rarely, a macular hole caused by retinal thinning. Imaging of the central and peripheral retina including 'red-free' views is a rapid, noninvasive and inexpensive test that might aid the diagnosis of Alport syndrome, particularly in male individuals with early-onset renal failure. The assistance of an interested ophthalmologist is invaluable in the diagnosis of Alport syndrome.

Alport syndrome: a review

Alport syndrome, a hereditary nephritis accompanied by high-tone sensorineural deafness and distinctive ocular signs was first noted in the literature during the early 1900s. This disease is caused by a genetic defect in Type IV collagen which makes up basement membranes in many body systems. The patient will usually have bilateral anterior lenticonus causing varied refractive errors. You may also note yellow-white to silver flecks within the macular and midperipheral regions of the retina. The treatment of the visual problems is an important but secondary concern due to the seriousness of the systemic disease. Dual sensory loss, however, creates an urgent need for appropriate vision care. Due to the high risk for developmental delay and decreased social integration, early intervention should be considered in the treatment plan. Coping strategies for the patient (and the family) need to be addressed because of the chronicity of this syndrome. The primary care optometrist will be challenged by the individual with Alport syndrome since a balance between oculo-visual, developmental/psycho-educational and systemic care is required. A multi-disciplinary approach by the healthcare management team will enhance the quality of life and positive outcomes for these patients.

First Open-Heart Surgery in Alport Syndrome

We report the first case of open-heart surgery in a patient with Alport syndrome, which refers to the clinical triad of hereditary nephritis, sensory neural deafness, and ocular abnormalities. The conduct of cardiopulmonary bypass, the bleeding tendency, and the precautions taken in a patient with end-stage renal failure are discussed.