Tips for Testing Adults With Suspected Genetic Kidney Disease.

Genetic kidney disease is common but often unrecognized. It accounts for most cystic kidney diseases and tubulopathies, many forms of congenital abnormalities of the kidney and urinary tract (CAKUT), and some glomerulopathies. Genetic kidney disease is typically suspected where the disease usually has a genetic basis or there is another affected family member, a young age at onset, or extrarenal involvement, but there are also many exceptions to these "rules". Genetic testing requires the patient's written informed consent. When a patient declines testing, another later conversation may be worthwhile. Genetic testing not only indicates the diagnosis but also the inheritance pattern, likely at-risk family members, disease in other organs, clinical course, and possibly effective treatments. Sometimes genetic testing does not identify a pathogenic variant even where other evidence is strong. A variant of uncertain significance (VUS) may be reported but should not be used for clinical decision making. It may be reclassified after more information becomes available without necessarily retesting the patient. Patients should be provided with a copy of their genetic test report, the results explained, and at-risk family members offered "cascade" testing. A referral to a clinical geneticist or genetic counselor helps identify affected family members and in providing advice to assist with reproductive decisions.

Ocular manifestations of congenital anomalies of the kidney and urinary tract (CAKUT).

Congenital anomalies of the kidney and urinary tract (CAKUT) are among the most common birth defects worldwide and a major cause of kidney failure in children. Extra-renal manifestations are also common. This study reviewed diseases associated with the Genomics England CAKUT-associated gene panel for ocular anomalies. In addition, each gene was examined for expression in the human retina and an ocular phenotype in mouse models using the Human Protein Atlas and Mouse Genome Informatics databases, respectively. Thirty-four (54%) of the 63 CAKUT-associated genes (55 'green' and 8 'amber') had a reported ocular phenotype. Five of the 6 most common CAKUT-associated genes (PAX2, EYA1, SALL1, GATA3, PBX1) that represent 30% of all diagnoses had ocular features. The ocular abnormalities found with most CAKUT-associated genes and with five of the six commonest were coloboma, microphthalmia, optic disc anomalies, refraction errors (astigmatism, myopia, and hypermetropia), and cataract. Seven of the CAKUT-associated genes studied (11%) had no reported ocular features but were expressed in the human retina or had an ocular phenotype in a mouse model, which suggested further possibly-unrecognised abnormalities. About one third of CAKUT-associated genes (18, 29%) had no ocular associations and were not expressed in the retina, and the corresponding mouse models had no ocular phenotype. Ocular abnormalities in individuals with CAKUT suggest a genetic basis for the disease and sometimes indicate the affected gene. Individuals with CAKUT often have ocular abnormalities and may require an ophthalmic review, monitoring, and treatment to preserve vision.

Ocular manifestations of renal ciliopathies.

Renal ciliopathies are a common cause of kidney failure in children and adults, and this study reviewed their ocular associations. Genes affected in renal ciliopathies were identified from the Genomics England Panels. Ocular associations were identified from Medline and OMIM, and the genes additionally examined for expression in the human retina ( https://www.proteinatlas.org/humanproteome/tissue ) and for an ocular phenotype in mouse models ( http://www.informatics.jax.org/ ). Eighty-two of the 86 pediatric-onset renal ciliopathies (95%) have an ocular phenotype, including inherited retinal degeneration, oculomotor disorders, and coloboma. Diseases associated with pathogenic variants in ANK6, MAPKBP1, NEK8, and TCTN1 have no reported ocular manifestations, as well as low retinal expression and no ocular features in mouse models. Ocular abnormalities are not associated with the most common adult-onset "cystic" kidney diseases, namely, autosomal dominant (AD) polycystic kidney disease and the AD tubulointerstitial kidney diseases (ADTKD). However, other kidney syndromes with cysts have ocular features including papillorenal syndrome (optic disc dysplasia), Hereditary Angiopathy Nephropathy, Aneurysms and muscle Cramps (HANAC) (tortuous retinal vessels), tuberous sclerosis (retinal hamartomas), von Hippel-Lindau syndrome (retinal hemangiomas), and Alport syndrome (lenticonus, fleck retinopathy). Ocular abnormalities are associated with many pediatric-onset renal ciliopathies but are uncommon in adult-onset cystic kidney disease. However the demonstration of ocular manifestations may be helpful diagnostically and the features may require monitoring or treatment.

Ocular manifestations of the genetic causes of focal and segmental glomerulosclerosis.

Genetic forms of focal and segmental glomerulosclerosis (FSGS) often have extra-renal manifestations. This study examined FSGS-associated genes from the Genomics England Renal proteinuria panel for reported and likely ocular features. Thirty-two of the 55 genes (58%) were associated with ocular abnormalities in human disease, and a further 12 (22%) were expressed in the retina or had an eye phenotype in mouse models. The commonest genes affected in congenital nephrotic syndrome (NPHS1, NPHS2, WT1, LAMB2, PAX2 but not PLCE1) may have ocular manifestations . Many genes affected in childhood-adolescent onset FSGS (NPHS1, NPHS2, WT1, LAMB2, SMARCAL1, NUP107 but not TRPC6 or PLCE1) have ocular features. The commonest genes affected in adult-onset FSGS (COL4A3-COL4A5, GLA ) have ocular abnormalities but not the other frequently affected genes (ACTN4, CD2AP, INF2, TRPC6). Common ocular associations of genetic FSGS include cataract, myopia, strabismus, ptosis and retinal atrophy. Mitochondrial forms of FSGS (MELAS, MIDD, Kearn's Sayre disease) are associated with retinal atrophy and inherited retinal degeneration. Some genetic kidney diseases (CAKUT, ciliopathies, tubulopathies) that result in secondary forms of FSGS also have ocular features. Ocular manifestations suggest a genetic basis for FSGS, often help identify the affected gene, and prompt genetic testing. In general, ocular abnormalities require early evaluation by an ophthalmologist, and sometimes, monitoring or treatment to improve vision or prevent visual loss from complications. In addition, the patient should be examined for other syndromic features and first degree family members assessed.

Prevalence Estimates of Predicted Pathogenic COL4A3-COL4A5 Variants in a Population Sequencing Database and Their Implications for Alport Syndrome.

BACKGROUND: The reported prevalence of Alport syndrome varies from one in 5000 to one in 53,000 individuals. This study estimated the frequencies of predicted pathogenic COL4A3-COL4A5 variants in sequencing databases of populations without known kidney disease. METHODS: Predicted pathogenic variants were identified using filtering steps based on the ACMG/AMP criteria, which considered collagen IV α3-α5 position 1 Gly to be critical domains. The population frequencies of predicted pathogenic COL4A3-COL4A5 variants were then determined per mean number of sequenced alleles. Population frequencies for compound heterozygous and digenic combinations were calculated from the results for heterozygous variants. RESULTS: COL4A3-COL4A5 variants resulting in position 1 Gly substitutions were confirmed to be associated with hematuria (for each, P<0.001). Predicted pathogenic COL4A5 variants were found in at least one in 2320 individuals. p.(Gly624Asp) represented nearly half (16 of 33, 48%) of the variants in Europeans. Most COL4A5 variants (54 of 59, 92%) had a biochemical feature that potentially mitigated the clinical effect. The predicted pathogenic heterozygous COL4A3 and COL4A4 variants affected one in 106 of the population, consistent with the finding of thin basement membrane nephropathy in normal donor kidney biopsy specimens. Predicted pathogenic compound heterozygous variants occurred in one in 88,866 individuals, and digenic variants in at least one in 44,793. CONCLUSIONS: The population frequencies for Alport syndrome are suggested by the frequencies of predicted pathogenic COL4A3-COL4A5 variants, but must be adjusted for the disease penetrance of individual variants and for the likelihood of already diagnosed disease and non-Gly substitutions. Disease penetrance may depend on other genetic and environmental factors.

Pathogenic Variants in the Genes Affected in Alport Syndrome (COL4A3-COL4A5) and Their Association With Other Kidney Conditions: A Review.

Massively parallel sequencing identifies pathogenic variants in the genes affected in Alport syndrome (COL4A3-COL4A5) in as many as 30% of individuals with focal and segmental glomerulosclerosis (FSGS), 10% of those with kidney failure of unknown cause, and 20% with familial immunoglobulin A (IgA) glomerulonephritis. FSGS associated with COL4A3-COL4A5 variants is usually present by the onset of kidney failure and may develop because the abnormal glomerular membranes result in podocyte loss and secondary hyperfiltration. The association of COL4A3-COL4A5 variants with kidney failure or IgA glomerulonephritis may be coincidental. However, pathogenic variants in these conditions occur more often than they should by chance, which suggests that the variants are disease-causing. COL4A3-COL4A5 variants are also found in cystic kidney diseases after autosomal dominant polycystic kidney disease has been excluded. COL4A3-COL4A5 variants should be suspected in individuals with FSGS, kidney failure of unknown cause, or familial IgA glomerulonephritis, especially where there is persistent hematuria and a family history of hematuria or kidney failure.

Alport syndrome: deducing the mode of inheritance from the presence of haematuria in family members.

The diagnosis of Alport syndrome is suspected when an individual has haematuria or renal failure, together with a hearing loss; haematuria or renal failure, and a family history of Alport syndrome; or a pathognomonic Alport feature, such as lenticonus, fleck retinopathy, a lamellated glomerular basement membrane (GBM), or a GBM that lacks the collagen IV α3α4α5 network. The diagnosis of Alport syndrome is optimally confirmed by the demonstration of a mutation in the COL4A5 gene or two mutations in trans in the COL4A3 or COL4A4 genes. In practice, genetic testing for Alport syndrome is not widely available, and even with testing, causative mutations are not demonstrated in 5% of cases. Often, haematuria is only known in some family members, and the other characteristic features are not present or have not been sought. Where Alport syndrome remains likely, it is important to distinguish between X-linked inheritance, which occurs in 85% of families, and autosomal recessive inheritance, in the remaining 15%. This distinction is important because different modes of inheritance mean that different family members are at risk of being affected. Clinicians generally rely on the presence of haematuria to identify affected individuals in families with suspected Alport syndrome and on the information from three-generational family trees to assess the likely mode of inheritance. While often helpful, this strategy can also be misleading. The major sources of error are families with few members or where few members are tested; families comprising mainly women, where the typical Alport features are absent; families where the father is not available for testing for haematuria; and families with a coincidental renal disease. These difficulties emphasise the helpfulness of genetic testing in distinguishing between X-linked and autosomal recessively inherited forms of Alport syndrome.

Expert consensus guidelines for the genetic diagnosis of Alport syndrome.

Recent expert guidelines recommend genetic testing for the diagnosis of Alport syndrome. Here, we describe current best practice and likely future developments. In individuals with suspected Alport syndrome, all three COL4A5, COL4A3 and COL4A4 genes should be examined for pathogenic variants, probably by high throughput-targeted next generation sequencing (NGS) technologies, with a customised panel for simultaneous testing of the three Alport genes. These techniques identify up to 95% of pathogenic COL4A variants. Where causative pathogenic variants cannot be demonstrated, the DNA should be examined for deletions or insertions by re-examining the NGS sequencing data or with multiplex ligation-dependent probe amplification (MLPA). These techniques identify a further 5% of variants, and the remaining few changes include deep intronic splicing variants or cases of somatic mosaicism. Where no pathogenic variants are found, the basis for the clinical diagnosis should be reviewed. Genes in which mutations produce similar clinical features to Alport syndrome (resulting in focal and segmental glomerulosclerosis, complement pathway disorders, MYH9-related disorders, etc.) should be examined. NGS approaches have identified novel combinations of pathogenic variants in Alport syndrome. Two variants, with one in COL4A3 and another in COL4A4, produce a more severe phenotype than an uncomplicated heterozygous change. NGS may also identify further coincidental pathogenic variants in genes for podocyte-expressed proteins that also modify the phenotype. Our understanding of the genetics of Alport syndrome is evolving rapidly, and both genetic and non-genetic factors are likely to contribute to the observed phenotypic variability.

Hypertensive/Microvascular Disease and COPD: a Case Control Study.

BACKGROUND/AIMS: This study tested the hypothesis that individuals with chronic obstructive pulmonary disease (COPD) have more small vessel disease and more severe disease than an age- and gender- matched hospital patient comparison group. METHODS: This was a single centre, case-control study of 151 individuals with COPD (FEV1/VC) < 0.7 recruited consecutively immediately after respiratory function tests at a Melbourne teaching hospital over a 4 month period in 2010. Controls were individuals with normal respiratory function tests recruited contemporaneously from the same centre. Retinal images were obtained with a nonmydriatic camera (KOWA or Canon CR5-45NM), deidentiifed and graded by two trained graders for microvascular retinopathy (Wong and Mitchell classification), and vessel calibre using a computer-assisted method and Knudtson's modification of the Parr-Hubbard formula. Differences in microvascular retinopathy and vessel calibre between COPD patients and the comparison group were examined using Fisher's exact test or the t test (StataCorp, Texas). RESULTS: Patients with COPD had more microvascular retinopathy (121, 80% and 76, 50%; OR 3.98, 95%CI 2.39 to 6.64) and more severe disease (42, 28% and 18, 12%; OR 2.85, 95% CI 1.55 to 5.23) than other hospital patients. COPD remained an independent determinant of microvascular retinopathy (OR 4.56, 95%CI 2.49 to 8.36) after adjusting for gender, hypertension, smoking, and diabetes duration. Retinal arterioles and venules were wider in patients with COPD than other hospital patients (mean difference +6.5 µm, 95% confidence interval 1.4 to 11.6; and +17.4 µm, 95%CI 9.4 to 25.5, respectively). Larger venules were more common in younger individuals (+0.6 µm, 0.1 to 1.17) with more cigarette exposure (+0.3 µm, 0.2 to 0.5) or a lower serum albumin (+23.0 µm, 6.0 to 40.0). Venular calibre was not different in current and former smokers (p=0.77). There were trends for venules to be larger with more severe COPD (lower FEV1/VC, p=0.09) and with CT-demonstrated emphysema (p=0.06). CONCLUSIONS: Hypertensive/microvascular disease is more common and more severe in patients with COPD. This is likely to contribute to the associated increase in cardiac risk.

Identifying and integrating consumer perspectives in clinical practice guidelines on autosomal-dominant polycystic kidney disease.

AIM: This study aimed to identify consumer perspectives on topics and outcomes to integrate in the Kidney Health Australia Caring for Australasians with Renal Impairment (KHA-CARI) clinical practice guidelines on autosomal-dominant polycystic kidney disease (ADPKD). METHODS: A workshop involving three concurrent focus groups with 18 consumers (patients with ADPKD (n = 15), caregivers (n = 3)) was convened. Guideline topics, interventions and outcomes were identified, and integrated into guideline development. Thematic analysis was used to analyse the reasons for their choices. RESULTS: Twenty-two priority topics were identified, with most focussed on non-pharmacological management (diet, fluid intake, physical activity, complementary medicine), pain management and psychosocial care (mental health, counselling, cognitive and behavioural training, education, support groups). They also identified 26 outcomes including quality of life (QoL), progression of kidney disease, kidney function, cyst growth and nephrotoxity. Almost all topics and outcomes suggested were identified by health professionals with the exception of five topics/outcomes. Six themes reflected reasons for their choices: clarifying ambiguities, resolving debilitating pain, concern for family, preparedness for the future, taking control and significance of impact. CONCLUSION: Although there was considerable concordance between the priority topics and outcomes of health professionals and consumers for guidelines of ADPKD, there was also important discordance with consumers focused on fewer issues, but particularly on lifestyle, psychosocial support, pain, and QoL and renal outcomes. Active consumer engagement in guidelines development can help to ensure the inclusion of patient-centred recommendations, which may lead to better management of disease progression, symptoms, complications, and psychosocial impact.

Microvascular Disease After Renal Transplantation.

BACKGROUND/AIMS: Individuals who reach end-stage kidney disease (CKD5) have a high risk of vascular events that persists even after renal transplantation. This study compared the prevalence and severity of microvascular disease in transplant recipients and patients with CKD5. METHODS: Individuals with a renal transplant or CKD5 were recruited consecutively from renal clinics, and underwent bilateral retinal photography (Canon CR5-45, Canon). Their retinal images were deidentified and reviewed for hypertensive/microvascular signs by an ophthalmologist and a trained grader (Wong and Mitchell classification), and for vessel caliber at a grading centre using a computer-assisted method and Knudtson's modification of the Parr-Hubbard formula. RESULTS: Ninety-two transplant recipients (median duration 6.4 years, range 0.8 to 28.8) and 70 subjects with CKD5 were studied. Transplant recipients were younger (p<0.001), with a higher eGFR (p< 0.001), but were just as likely to have a moderate-severe hypertensive/microvascular retinopathy (46/92, 50%) as subjects with CKD5 (38/70, 54%; OR 0.84, CI 0.45 to 1.57, p=0.64), and had similar mean arteriole and venular calibres (135.1 ± 7.5 µm and 137.9 ± 14.9 µm, p=0.12; and 199.1 ± 17.8 µm and 202.4 ± 27.8 µm, p=0.36, respectively). Arteriole and venular caliber were not different in nine patients examined before and after transplantation (p=0.62 and p=0.11, respectively). CONCLUSIONS: Hypertensive/microvascular disease occurred just as often and was generally as severe in transplant recipients and subjects with CKD5. Microvascular disease potentially contributes to increased cardiac events post-transplantation.

The Human Variome Project: ensuring the quality of DNA variant databases in inherited renal disease.

A recent review identified 60 common inherited renal diseases caused by DNA variants in 132 different genes. These diseases can be diagnosed with DNA sequencing, but each gene probably also has a thousand normal variants. Many more normal variants have been characterised by individual laboratories than are reported in the literature or found in publicly accessible collections. At present, testing laboratories must assess each novel change they identify for pathogenicity, even when this has been done elsewhere previously, and the distinction between normal and disease-associated variants is particularly an issue with the recent surge in exomic sequencing and gene discovery projects. The Human Variome Project recommends the establishment of gene-specific DNA variant databases to facilitate the sharing of DNA variants and decisions about likely disease causation. Databases improve diagnostic accuracy and testing efficiency, and reduce costs. They also help with genotype-phenotype correlations and predictive algorithms. The Human Variome Project advocates databases that use standardised descriptions, are up-to-date, include clinical information and are freely available. Currently, the genes affected in the most common inherited renal diseases correspond to 350 different variant databases, many of which are incomplete or have insufficient clinical details for genotype-phenotype correlations. Assistance is needed from nephrologists to maximise the usefulness of these databases for the diagnosis and management of inherited renal disease.

Mutation databases for inherited renal disease: are they complete, accurate, clinically relevant, and freely available?

This study examined whether gene-specific DNA variant databases for inherited diseases of the kidney fulfilled the Human Variome Project recommendations of being complete, accurate, clinically relevant and freely available. A recent review identified 60 inherited renal diseases caused by mutations in 132 genes. The disease name, MIM number, gene name, together with "mutation" or "database," were used to identify web-based databases. Fifty-nine diseases (98%) due to mutations in 128 genes had a variant database. Altogether there were 349 databases (a median of 3 per gene, range 0-6), but no gene had two databases with the same number of variants, and 165 (50%) databases included fewer than 10 variants. About half the databases (180, 54%) had been updated in the previous year. Few (77, 23%) were curated by "experts" but these included nine of the 11 with the most variants. Even fewer databases (41, 12%) included clinical features apart from the name of the associated disease. Most (223, 67%) could be accessed without charge, including those for 50 genes (40%) with the maximum number of variants. Future efforts should focus on encouraging experts to collaborate on a single database for each gene affected in inherited renal disease, including both unpublished variants, and clinical phenotypes.

Alport syndrome: its effects on the glomerular filtration barrier and implications for future treatment.

The glomerular filtration barrier comprises a fenestrated capillary endothelium, glomerular basement membrane and podocyte slit diaphragm. Over the past decade we have come to realise that permselectivity depends on size and not necessarily charge, that the molecular sieve depends on the podocyte contractile apparatus and is highly dynamic, and that protein uptake by proximal tubular epithelial cells stimulates signalling and the production of transcription factors and inflammatory mediators. Alport syndrome is the second commonest monogenic cause of renal failure after autosomal dominant polycystic kidney disease. Eighty per cent of patients have X-linked disease caused by mutations in the COL4A5 gene. Most of these result in the replacement of the collagen IV α3α4α5 network with the α1α1α2 heterotrimer. Affected membranes also have ectopic laminin and increased matrix metalloproteinase levels, which makes them more susceptible to proteolysis. Mechanical stress, due to the less elastic membrane and hypertension, interferes with integrin-mediated podocyte-GBM adhesion. Proteinuria occurs when urinary levels exceed tubular reabsorption rates, and initiates tubulointerstitial fibrosis. The glomerular mesangial cells produce increased TGFß and CTGF which also contribute to glomerulosclerosis. Currently there is no specific therapy for Alport syndrome. However treatment with angiotensin converting enzyme (ACE) inhibitors delays renal failure progression by reducing intraglomerular hypertension, proteinuria, and fibrosis. Our greater understanding of the mechanisms underlying the GBM changes and their consequences in Alport syndrome have provided us with further novel therapeutic targets.

Clinical and genetic features in autosomal recessive and X-linked Alport syndrome.

BACKGROUND: This study determined the family history and clinical features that suggested autosomal recessive rather than X-linked Alport syndrome. METHODS: All patients had the diagnosis of Alport syndrome and the mode of inheritance confirmed by genetic testing, and underwent examination at a single centre. RESULTS: Patients comprised 9 males and 6 females with autosomal recessive Alport syndrome, and 18 males and 22 females with X-linked disease. Fourteen (93 %) individuals with autosomal recessive Alport syndrome developed early end-stage renal failure, all 15 had hearing loss, and most had lenticonus (12, 80 %), and a central (13, 87 %) or peripheral (13, 87 %) retinopathy. These features occurred as often as in males with X-linked disease. Females with autosomal recessive inheritance were less likely to have an affected family member in another generation (p = 0.01) than females with X-linked disease. They were more likely to have renal failure (p = 0.003), hearing loss (p = 0.02) and lenticonus (p < 0.001). Fifty percent had a central retinopathy compared with 18 % with X-linked disease (p = 0.14), but peripheral retinopathy prevalence was not different (p = 0.64). Nonsense mutations accounted for 67 % (8/12) of these disease-causing mutations. CONCLUSIONS: Autosomal recessive inheritance is increased in females with Alport syndrome and early onset renal failure, hearing loss, lenticonus, and, possibly, central retinopathy.

A female with X-linked Alport syndrome and compound heterozygous COL4A5 mutations.

BACKGROUND: Female subjects with X-linked Alport syndrome have a single COL4A5 mutation, germ cell mosaicism in affected tissues and typically develop renal failure later or less often than male subjects. Women with two mutations are exceedingly rare, and usually have consanguineous parents or uniparental disomy. We describe here a 20-year-old woman who inherited two different COL4A5 variants, one from her father (c.2677G>C) and one from her mother (c.384 +1 G>A). CASE-DIAGNOSIS/TREATMENT: The index case had normal renal function, proteinuria and no clinically detectable hearing loss, or ocular abnormalities. Her father and paternal uncle developed end-stage renal disease at 37 and 28 years respectively, together with hearing loss, but not lenticonus or central retinopathy. Her mother had mildly impaired renal function, proteinuria, hearing loss, but no ocular abnormalities. Her maternal grandfather and 22-year-old brother, both with this mutation, developed renal failure by 28 years with hearing loss, or had proteinuria and hearing loss respectively. CONCLUSION: The index case has clinical features consistent with germ cell mosaicism of two COL45A mutations associated with adult-onset renal failure, but no ocular abnormalities. Her risk of renal failure is high, but the rate of progression to end-stage disease depends on the underlying mutations, and disease modification with renin-angiotensin blockade.

DNA variant databases improve test accuracy and phenotype prediction in Alport syndrome.

X-linked Alport syndrome is a form of progressive renal failure caused by pathogenic variants in the COL4A5 gene. More than 700 variants have been described and a further 400 are estimated to be known to individual laboratories but are unpublished. The major genetic testing laboratories for X-linked Alport syndrome worldwide have established a Web-based database for published and unpublished COL4A5 variants ( https://grenada.lumc.nl/LOVD2/COL4A/home.php?select_db=COL4A5 ). This conforms with the recommendations of the Human Variome Project: it uses the Leiden Open Variation Database (LOVD) format, describes variants according to the human reference sequence with standardized nomenclature, indicates likely pathogenicity and associated clinical features, and credits the submitting laboratory. The database includes non-pathogenic and recurrent variants, and is linked to another COL4A5 mutation database and relevant bioinformatics sites. Access is free. Increasing the number of COL4A5 variants in the public domain helps patients, diagnostic laboratories, clinicians, and researchers. The database improves the accuracy and efficiency of genetic testing because its variants are already categorized for pathogenicity. The description of further COL4A5 variants and clinical associations will improve our ability to predict phenotype and our understanding of collagen IV biochemistry. The database for X-linked Alport syndrome represents a model for databases in other inherited renal diseases.

Expert guidelines for the management of Alport syndrome and thin basement membrane nephropathy.

Few prospective, randomized controlled clinical trials address the diagnosis and management of patients with Alport syndrome or thin basement membrane nephropathy. Adult and pediatric nephrologists and geneticists from four continents whose clinical practice focuses on these conditions have developed the following guidelines. The 18 recommendations are based on Level D (Expert opinion without explicit critical appraisal, or based on physiology, bench research, or first principles-National Health Service category) or Level III (Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees-U.S. Preventive Services Task Force) evidence. The recommendations include the use of genetic testing as the gold standard for the diagnosis of Alport syndrome and the demonstration of its mode of inheritance; the need to identify and follow all affected members of a family with X-linked Alport syndrome, including most mothers of affected males; the treatment of males with X-linked Alport syndrome and individuals with autosomal recessive disease with renin-angiotensin system blockade, possibly even before the onset of proteinuria; discouraging the affected mothers of males with X-linked Alport syndrome from renal donation because of their own risk of kidney failure; and consideration of genetic testing to exclude X-linked Alport syndrome in some individuals with thin basement membrane nephropathy. The authors recognize that as evidence emerges, including data from patient registries, these guidelines will evolve further.

COL4A3/COL4A4 mutations and features in individuals with autosomal recessive Alport syndrome.

Alport syndrome is an inherited disease characterized by hematuria, progressive renal failure, hearing loss, and ocular abnormalities. Autosomal recessive Alport syndrome is suspected in consanguineous families and when female patients develop renal failure. Fifteen percent of patients with Alport syndrome have autosomal recessive inheritance caused by two pathogenic mutations in either COL4A3 or COL4A4. Here, we describe the mutations and clinical features in 40 individuals including 9 children and 21 female individuals (53%) with autosomal recessive inheritance indicated by the detection of two mutations. The median age was 31 years (range, 6-54 years). The median age at end stage renal failure was 22.5 years (range, 10-38 years), but renal function was normal in nine adults (29%). Hearing loss and ocular abnormalities were common (23 of 35 patients [66%] and 10 of 18 patients [56%], respectively). Twenty mutation pairs (50%) affected COL4A3 and 20 pairs affected COL4A4. Of the 68 variants identified, 39 were novel, 12 were homozygous changes, and 9 were present in multiple individuals, including c.2906C>G (p.(Ser969*)) in COL4A4, which was found in 23% of the patients. Thirty-six variants (53%) resulted directly or indirectly in a stop codon, and all 17 individuals with early onset renal failure had at least one such mutation, whereas these mutations were less common in patients with normal renal function or late-onset renal failure. In conclusion, patient phenotypes may vary depending on the underlying mutations, and genetic testing should be considered for the routine diagnosis of autosomal recessive Alport syndrome.

Drusen and Other Retinal Findings in People With IgA Glomerulonephritis.

PURPOSE: Retinal drusen have been described in people with IgA nephropathy. We examined the frequency of drusen in IgA nephropathy and compared their location and composition with those for drusen in age-related macular degeneration. DESIGN: Immunohistological case series of eyes of patients with IgA nephropathy, and a comparison eye with age-related macular degeneration. METHODS: Donor eyes from 4 individuals (3 male, 1 female, aged 40-80 years) with biopsy-proven IgA nephropathy and kidney failure were examined for the presence of drusen, and location and composition using antibodies for vitronectin, IgA, IgM, IgG, C3, and C1q. Results were compared with those for drusen in macular degeneration without IgA nephropathy. RESULTS: All 4 donors had sparse, subretinal pigment epithelium drusen of 55-65 mm diameter that stained for vitronectin but not for IgA or complement. All donors had retinal capillaries and choriocapillaris staining for IgA. The youngest donor (female, 40) had rare deposits in the outer nuclear layer that stained for IgA, but not for vitronectin. The oldest donor (male, 82) had large cystlike spaces in the inner nuclear and plexiform layers, and smaller cysts in the outer nuclear layer, with no staining for IgA or complement. CONCLUSIONS: Retinal drusen are uncommon in IgA nephropathy, even with kidney failure. Drusen in IgA nephropathy resemble drusen found in age-related macular degeneration. IgA-staining deposits in the outer nuclear layer were likely due to systemic deposition of IgA and complement activation. The nature of cystic spaces is unknown. Further analysis of the retinas of people with glomerulonephritis is recommended.