The use of ocular abnormalities to diagnose X-linked Alport syndrome in children

Alport Syndrome: Clinical Spectrum and Therapeutic Advances

Alport syndrome is a hereditary disorder characterized by kidney disease, ocular abnormalities, and sensorineural hearing loss. Work in understanding the cause of Alport syndrome and the molecular composition of the glomerular basement membrane ultimately led to the identification of COL4A3, COL4A4 (both on chromosome 2q36), and COL4A5 (chromosome Xq22), encoding the α3, α4, and α5 chains of type IV collagen, as the responsible genes. Subsequent studies suggested that autosomal recessive Alport syndrome and males with X-linked Alport syndrome have more severe disease, whereas autosomal dominant Alport syndrome and females with X-linked Alport syndrome have more variability. Variant type is also influential-protein-truncating variants in autosomal recessive Alport syndrome or males with X-linked Alport syndrome often present with severe symptoms, characterized by kidney failure, extrarenal manifestations, and lack of the α3-α4-α5(IV) network. By contrast, mild-moderate forms from missense variants display α3-α4-α5(IV) in the glomerular basement membrane and are associated with protracted kidney involvement without extrarenal manifestations. Regardless of type, therapeutic intervention for kidney involvement is focused on early initiation of angiotensin-converting enzyme inhibitors. There are several therapies under investigation including sodium/glucose cotransporter 2 inhibitors, aminoglycoside analogs, endothelin type A antagonists, lipid-modifying drugs, and hydroxychloroquine, although targeting the underlying defect through gene therapy remains in preclinical stages.

[Ocular alterations in patients with Alport syndrome-An update]

BACKGROUND AND OBJECTIVE

Alport syndrome (AS) is a rare hereditary systemic disease that results in alterations of the kidneys, inner ear, and various structures of the eye. It is caused by mutations in one of the genes encoding collagen type IV. In recent years, new and innovative imaging techniques have added characteristics of ocular alterations in AS and provided new insights, including into the pathogenesis of the disease. The aim of this paper is to provide an overview of the current knowledge of ocular changes in AS, as well as to present the Alport ocular pass.

METHOD

Narrative review article.

RESULTS

Ocular manifestations of AS include changes in the cornea, lens, and retina. Specifically, posterior polymorphic corneal dystrophy, anterior lenticonus (pathognomonic for AS), and various retinal changes have been described, which have been further characterized in recent years by newer imaging techniques. In particular, foveal changes in AS may present as both a thickened central retina in the context of foveal hypoplasia or a staircase-like thinning of the fovea. Both lesions could provide further insights into the role of type IV collagen in ocular structures.

CONCLUSION

The AS can manifest in various structures of the eye. The staircase-like changes of the central retina in AS patients indicate the important role of collagen type IV in the homeostasis and regular function of the inner retinal layers. The often mild foveal hypoplasia may provide clues to the role of collagen type IV in retinal embryogenesis. While anterior lenticonus is pathognomonic for AS and can be treated easily by refractive lens exchange, the only option currently available for retinal alterations is close follow-up and, if necessary, treatment of systemic complications of AS.

Guidelines for Genetic Testing and Management of Alport Syndrome

Genetic testing for pathogenic COL4A3-5 variants is usually undertaken to investigate the cause of persistent hematuria, especially with a family history of hematuria or kidney function impairment. Alport syndrome experts now advocate genetic testing for persistent hematuria, even when a heterozygous pathogenic COL4A3 or COL4A4 is suspected, and cascade testing of their first-degree family members because of their risk of impaired kidney function. The experts recommend too that COL4A3 or COL4A4 heterozygotes do not act as kidney donors. Testing for variants in the COL4A3-COL4A5 genes should also be performed for persistent proteinuria and steroid-resistant nephrotic syndrome due to suspected inherited FSGS and for familial IgA glomerulonephritis and kidney failure of unknown cause.

Quantitative Optical Coherence Tomography Angiography Biomarkers for Alport Syndrome

PURPOSE

The aim of this study was to evaluate microvascular abnormalities of patients with Alport syndrome (AS) using optical coherence tomography angiography (OCT-A) quantitative biomarkers.

METHODS

This was cross sectional, prospective evaluation of consecutive patients with AS and healthy subjects. AS diagnosis was performed by the genetic test. All participants underwent a retinal vasculature evaluation by spectral-domain optical coherence tomography (SD-OCT) and OCT-A of the macula. Quantitative analysis included whole vascular density, foveal avascular zone area, fractal dimension (FD), and lacunarity (LAC).

RESULTS

Ninety-four eyes were included in this study, 45 eyes from patients with AS and 49 eyes from healthy subjects. The pathogenic mutation in the COL4A5 gene on the chromosome X was found in 14 patients; the pathogenic autosomal recessive mutations in the COL4A3 gene were found in 9 patients. Quantitative evaluation demonstrated a significant difference between AS and healthy subjects on LAC of the superficial capillary plexus and deep capillary plexus (DCP) (p < 0.001 and p < 0.001, respectively) and on FD in the DCP (p < 0.001).

CONCLUSION

The DCP Alport patients have a higher vessel nonuniformity than DCP of healthy subjects. We hypothesize that endothelial cell lesion in the setting of low resistance at the DCP circuit could lead to long-term structural disorganization.

Bilateral spontaneous anterior lens capsule ruptures in a child: A rare presentation of Alport syndrome

Purpose

This report describes the rare case of a child with bilateral spontaneous anterior lens capsule ruptures as the presenting feature of Alport syndrome.

Observations

The clinical presentation, special investigations and surgical management of the child are described, accompanied by a brief discussion of the genetic basis for the ocular and systemic manifestations of Alport syndrome.

Conclusions

Bilateral spontaneous anterior lens capsule ruptures as the presenting feature of Alport syndrome has not been described before.

Bilateral giant macular holes: A rare manifestation of Alport syndrome

PURPOSE:

Alport syndrome is a rare condition characterized by the clinical triad of nephritic syndrome, sensorineural deafness, and ophthalmological alterations. Herein, we present a rare case of a patient diagnosed with Alport syndrome and bilateral giant macular holes.

CASE DESCRIPTION:

A 40-year-old woman with a previously unreported mutation in the COL4A4 gene suggestive of autosomal-recessive Alport syndrome presented at our department. The patient exhibited bilateral full-thickness macular holes measuring >1500 µm at their smallest diameters. The very large dimensions of both macular holes were indicative of a bad prognosis regarding hole closure, and a conservative approach was adopted. The patient was maintained on renal substitution therapy, and genetic counseling was offered to other family members.

CONCLUSION:

Ophthalmological findings associated to Alport syndrome commonly include anterior lenticonus and dot-and-fleck retinopathy, although giant macular holes can also be associated with this condition. A multidisciplinary approach is crucial in the management of these patients, as Alport syndrome is an inherited systemic basement membrane disease.

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.

Autofluorescence and spectral domain OCT findings in Alport syndrome

PURPOSE

The purpose of this study was to report novel autofluorescence and spectral domain optic coherence tomography findings in a case of Alport syndrome.

METHODS

Case report and literature review.

RESULTS

A 30-year-old woman with a history of Alport syndrome presented with a full-thickness macular hole in her right eye and evidence of vitreofoveal traction in her asymptomatic left eye. Both eyes had temporal macular thinning. She had anterior lenticonus and perimacular flecks characteristic of Alport syndrome. In addition, fundus autofluorescence revealed an interesting pattern of splotchy hypoautofluorescence in the periphery (in the absence of any peripheral retinopathy on examination), which has not been described previously.

CONCLUSION

Macular hole in Alport syndrome results from basement membrane weakness and an abnormal vitreoretinal interface. Although this makes surgery in these cases challenging, careful separation of the posterior hyaloid and internal limiting membrane peeling with fluid gas exchange can lead to successful closure. Alport syndrome can also cause abnormalities in the retinal pigment epithelium/Bruch membrane leading to abnormal autofluorescence.

Phacoemulsification in a Rare Case of Alport's Syndrome

AIM

To report a rare case of Alport Syndrome (AS) highlighting the precautions and surgical complications during phacoemulsification.

METHOD

A 35 year old female presented with bilateral painless progressive diminution of vision since 6 months and had bilateral deafness since 12 years. Best corrected visual acuity (BCVA) in both the eyes was 4/60. Bilateral anterior lenticonus, posterior polar cataract with posterior lenticonus, macular and peripheral retinal flecks, which are rarely reported in females, were present. Right eye phacoemulsification and IOL implantation was done.

RESULT

During surgery capsulorrhexis underwent multiple dehiscence in a "flower petal pattern" due to fragile capsule. It was completed with microforceps under high viscocity viscoelastic. IOL was placed in sulcus due to extension of capsulorrhexis. BCVA was 6/12 at 1 month.

CONCLUSION

This rare case highlights the importance of an eye ailment in revealing an important systemic disease. It also highlights proper management of complications that can give good result even in difficult cases.

Alport syndrome--insights from basic and clinical research

In 1927, Arthur C. Alport first published his description of a triad of symptoms in a family with hereditary congenital haemorrhagic nephritis, deafness and ocular changes. A few years after his death, this group of symptoms was renamed Alport syndrome. To this day, Alport syndrome still inevitably leads to end-stage renal disease and the need for renal replacement therapy, starting in young adulthood. During the past two decades, research into this rare disease has focused on the effects of mutations in collagen type IV and the role of changes in podocytes and the glomerular basement membrane that lead to early kidney fibrosis. Animal models of Alport syndrome also demonstrate the pathogenetic importance of interactions between podocytes and the extracellular matrix. Such models might also help researchers to answer basic questions about podocyte function and the development of fibrosis, and to develop new therapeutic approaches that might be of use in other kidney diseases. In this Review, we discuss the latest basic and clinical research on Alport syndrome, focusing on the roles of podocyte pathology and the extracellular matrix. We also highlight early diagnosis and treatment options for young patients with this disorder.

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.