Non-syndromic inherited retinal diseases in Poland: Genes, mutations, and phenotypes.

Purpose: Inherited retinal diseases (IRDs), encompassing many clinical entities affecting the retina, are classified as rare disorders. Their extreme heterogeneity made molecular screening in the era before next-generation sequencing (NGS) expensive and time-consuming. Since then, many NGS studies of IRD molecular background have been conducted in Western populations; however, knowledge of the IRD mutational spectrum in Poland is still limited. Until now, there has been almost no comprehensive analysis of this particular population regarding the molecular basis and inheritance of IRDs. Therefore, the purpose of this study was to gain knowledge about the type and prevalence of causative variants in the Polish population. Methods: We recruited 190 Polish families with non-syndromic IRDs, including Stargardt disease (STGD), retinitis pigmentosa (RP), cone- and cone-rod dystrophy (CD/CRD), achromatopsia, and congenital stationary night blindness. A pool of molecular inversion probes was used, which targeted 108 genes associated with non-syndromic IRDs known in 2013. We applied filtering for known variants occurring with an allele frequency >0.5% in public and in-house databases, with the exception of variants in ABCA4, when the frequency filter was set to 3.0%. Hypomorphic p.(Asn1868Ile) was added manually. In the case of novel missense or splicing variants, we used in silico prediction software to assess mutation causality. Results: We detected causative mutations in 115 of the 190 families with non-syndromic IRD (60.2%). Fifty-nine individuals with STGD, RP, and CD/CRD carried causal variants in ABCA4. Novel single nucleotide variants were found in ABCA4, CEP290, EYS, MAK, and CNGA3. The complex allele c.[1622T>C;3113C>T], p.[Leu541Pro;Ala1038Val] was found in 33 individuals with ABCA4-associated disorders, which makes it the most prevalent allele in the Polish population (17% of all solved cases). Diagnosis was reevaluated in 16 cases. Conclusions: Previously, there were no comprehensive reports of IRDs in the Polish population. This study is the first to indicate that the most common IRDs in Poland are ABCA4-associated diseases, regardless of the phenotype. In Polish patients with RP, the second most prevalent causal gene was RHO and the third RPGR, while there were not as many mutations in EYS as in Western populations. The number of initial erroneous diagnoses may be the result of limited access to diagnostics with advanced tools, such as electroretinography; however, it is necessary to raise awareness among Polish ophthalmologists of rare IRDs. Additionally, it must be emphasized that in some cases genetic analysis of the patient is necessary to achieve an accurate diagnosis.

A Mild Phenotype Caused by Two Novel Compound Heterozygous Mutations in CEP290.

CEP290 is a ciliary gene frequently mutated in ciliopathies, resulting in a broad range of phenotypes, ranging from isolated inherited retinal disorders (IRDs) to severe or lethal syndromes with multisystemic involvement. Patients with non-syndromic CEP290-linked disease experience profound and early vision loss due to cone-rod dystrophy, as in Leber congenital amaurosis. In this case report, we describe two novel loss-of-function heterozygous alterations in the CEP290 gene, discovered in a patient suffering from retinitis pigmentosa using massive parallel sequencing of a molecular inversion probes library constructed for 108 genes involved in IRDs. A milder phenotype than expected was found in the individual, which serves to prove that some CEP290-associated disorders may display preserved cone function.

Genetic Spectrum of ABCA4-Associated Retinal Degeneration in Poland.

Mutations in retina-specific ATP-binding cassette transporter 4 (ABCA4) are responsible for over 95% of cases of Stargardt disease (STGD), as well as a minor proportion of retinitis pigmentosa (RP) and cone-rod dystrophy cases (CRD). Since the knowledge of the genetic causes of inherited retinal diseases (IRDs) in Poland is still scarce, the purpose of this study was to identify pathogenic ABCA4 variants in a subgroup of Polish IRD patients. We recruited 67 families with IRDs as a part of a larger study. The patients were screened with next generation sequencing using a molecular inversion probes (MIPs)-based technique targeting 108 genes involved in the pathogenesis of IRDs. All identified mutations were validated and their familial segregation was tested using Sanger sequencing. In the case of the most frequent complex allele, consisting of two variants in exon 12 and 21, familial segregation was tested using restriction fragment length polymorphism (RFLP). The most prevalent variant, a complex change c.[1622T>C;3113C>T], p.[Leu541Pro;Ala1038Val], was found in this cohort in 54% of all solved ABCA4-associated disorder cases, which is the highest frequency reported thus far. Additionally, we identified nine families displaying a pseudo-dominant mode of inheritance, indicating a high frequency of pathogenic variants within this population.

Stratifying risk for progression in IgA nephropathy: how to predict the future?

INTRODUCTION:  IgA nephropathy (IgAN) is characterized by a highly heterogeneous clinical course, which results in controversies regarding the assessment of individual prognosis and establishing the optimal treatment approach. OBJECTIVES:  The aim of the present study was to define risk factors for IgAN progression. We evaluated histopathological features derived from the Oxford classification of IgAN and additional, non­Oxford biopsy findings, as well as baseline and follow­up clinical data. PATIENTS AND METHODS:  We conducted a single­center retrospective study on 52 patients with biopsy­proven IgAN. The endpoint was an increase in serum creatinine levels of 50% from baseline. RESULTS:  Eight subjects (12%) reached the endpoint. Poor renal outcome was independently related to time­average proteinuria (TA­P) exceeding 2.0 g/d (P = 0.047), estimated glomerular filtration rate (eGFR) of less than 60 ml/min/1.73 m2 (P = 0.01), history of tonsillectomy (P = 0.01), and crescent lesions in renal biopsy (P = 0.03). High global sclerosis index (GSI) (P = 0.009), TA­P (P = 0.03), and the presence of microscopic hematuria (P = 0.03) were independent predictors of a more rapid rate of renal function loss, assessed by the velocity of eGFR decline. Of the variables included in the Oxford classification, only interstitial fibrosis and tubular atrophy proved to have prognostic value, as revealed by a univariate, but not multivariate Cox regression analysis. CONCLUSIONS:  The extent of proteinuria during follow­up and impaired renal function at the time of diagnosis remain the most significant clinical prognostic factors in IgAN. We also report additional, non­Oxford histopathological features that can be used for risk stratification in IgAN, including the GSI and the presence of crescents.