A founder COL4A3 pathogenic variant resulting in Alport syndrome and thin basement membrane disease: a case report series

Alport syndrome is a rare genetic condition characterized by kidney disease, hearing impairment, and ocular abnormalities. It exhibits various inheritance patterns involving pathogenic variants in COL4A3, COL4A4, and COL4A5 genes. The phenotypes can range from isolated hematuria with a non-progressive or very slowly progressive course to progressive kidney disease with extrarenal abnormalities. Timely diagnosis of Alport syndrome facilitates the early and effective implementation of treatment, as well as genetic counseling. Here, we report the COL4A3 c.765G > A, p.((=)) mutation in three ethnically Azerbaijani, apparently unrelated, consanguineous families from the village of Algeti in the Marneuli region of Georgia. We speculate that this variant could represent a founder mutation within this population and recommend offering genetic testing to Algeti village residents with persistent hematuria.

CHARACTERISTICS OF DIARRHEAL DISEASE COMPLICATED WITH HEMOLYTIC UREMIC SYNDROME AMONG CHILDREN IN GEORGIA, 2009-2016

Shiga toxin-producing Escherichia coli (STEC) causes illness ranging from mild diarrhea to bloody diarrhea, to the hemolytic uremic syndrome (HUS), which manifests with a triad of microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure. Surveillance of HUS and bloody diarrhea is not performed in Georgia. The primary objective of our study was to determine the annual incidence of diarrheal diseases. The secondary objective was to assess epidemiological characteristics, etiology and risk factors of diarrhea and HUS in Georgia among children under 15. We collected a retrospective data on diarrheal diseases particularly bloody diarrhea and HUS among children in Georgia in 2009-2016 years. Laboratory, clinical and epidemiological data was entered into electronic database. Descriptive statistics, proportions, incidence rates, means and medians were calculated in R statistical language using statistical package R for windows v 3.4.3. A total of 316 cases of bloody diarrhea including 64 (20.2%) cases complicated with HUS under age 15 were identified from 2009 until 2016. From 316 patients 5 (1.6%) have died, all of them with diagnosis and severe complications of HUS. Average rate of HUS per 100,000 populations during 2009-2016 was 0.3 and for bloody diarrhea 2 per 100,000. High RR for food products consumed by children with bloody diarrhea either complicated with HUS or not were various ice-creams produced locally (RR 4.23 P<0.001), dairy products (RR 2.79 P = 0.01), ground beef products (RR 4.52 P<0.001). The another highest attack ratio was identified for fruits (RR 6.19 P<0.001) and vegetables (RR 3.45 P < 0.001). Different enteric pathogens including shiga toxin producing E. coli was detected as etiology of diarrheal diseases and HUS. Epidemiological data suggests that inadequately washed fruits, vegetables and eating undercooked food and ice-cream could be a possible risk factors of exposure with enteric pathogens and developing diarrhea and HUS among children. Further investigations of food products are required to determine epidemiology and source food products of bloody diarrhea and HUS among children in Georgia.

EXPANDED PHENOTYPE OF TMEM67 GENE MUTATION (CASE REPORT)

Human ciliopathies are a class of multi-organ genetic disorders caused by defects of proteins expressed at the primary cilium, an organelle present on the cell surface of almost all cell types. Thus far, dozens of causative genes for ciliopathies have been identified and many of them are known to cause allelic disease. Of particular interest is the TMEM67 gene, encoding the transmembrane protein meckelin. The involvement of the mutant TMEM67 gene is known to be associated with a broad range of clinical presentations, namely Joubert syndrome 6 (JBTS6), nephronophthisis 11 (NPHP11), Bardet-Biedel syndrome (BBS), COACH syndrome, and lethal Meckel syndrome type 3 (MKS3). Here we present a case of a 3-year-old boy with compound heterozygous missense mutations in the TMEM67 gene manifesting features of both JBTS and NPHP syndromes, with neonatal onset of end-stage renal disease (ESRD) and associated microcephaly. Such a phenotype has not been reported to date, thus highlighting the diversity of ciliopathies and expanding the phenotype of the TMEM67 gene.

Spectrum of steroid-resistant and congenital nephrotic syndrome in children: the PodoNet registry cohort

BACKGROUND AND OBJECTIVES

Steroid-resistant nephrotic syndrome is a rare kidney disease involving either immune-mediated or genetic alterations of podocyte structure and function. The rare nature, heterogeneity, and slow evolution of the disorder are major obstacles to systematic genotype-phenotype, intervention, and outcome studies, hampering the development of evidence-based diagnostic and therapeutic concepts. To overcome these limitations, the PodoNet Consortium has created an international registry for congenital nephrotic syndrome and childhood-onset steroid-resistant nephrotic syndrome.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Since August of 2009, clinical, biochemical, genetic, and histopathologic information was collected both retrospectively and prospectively from 1655 patients with childhood-onset steroid-resistant nephrotic syndrome, congenital nephrotic syndrome, or persistent subnephrotic proteinuria of likely genetic origin at 67 centers in 21 countries through an online portal.

RESULTS

Steroid-resistant nephrotic syndrome manifested in the first 5 years of life in 64% of the patients. Congenital nephrotic syndrome accounted for 6% of all patients. Extrarenal abnormalities were reported in 17% of patients. The most common histopathologic diagnoses were FSGS (56%), minimal change nephropathy (21%), and mesangioproliferative GN (12%). Mutation screening was performed in 1174 patients, and a genetic disease cause was identified in 23.6% of the screened patients. Among 14 genes with reported mutations, abnormalities in NPHS2 (n=138), WT1 (n=48), and NPHS1 (n=41) were most commonly identified. The proportion of patients with a genetic disease cause decreased with increasing manifestation age: from 66% in congenital nephrotic syndrome to 15%-16% in schoolchildren and adolescents. Among various intensified immunosuppressive therapy protocols, calcineurin inhibitors and rituximab yielded consistently high response rates, with 40%-45% of patients achieving complete remission. Confirmation of a genetic diagnosis but not the histopathologic disease type was strongly predictive of intensified immunosuppressive therapy responsiveness. Post-transplant disease recurrence was noted in 25.8% of patients without compared with 4.5% (n=4) of patients with a genetic diagnosis.

CONCLUSIONS

The PodoNet cohort may serve as a source of reference for future clinical and genetic research in this rare but significant kidney disease.

Genetic screening in adolescents with steroid-resistant nephrotic syndrome

Genetic screening paradigms for congenital and infantile nephrotic syndrome are well established; however, screening in adolescents has received only minor attention. To help rectify this, we analyzed an unselected adolescent cohort of the international PodoNet registry to develop a rational screening approach based on 227 patients with nonsyndromic steroid-resistant nephrotic syndrome aged 10-20 years. Of these, 21% had a positive family history. Autosomal dominant cases were screened for WT1, TRPC6, ACTN4, and INF2 mutations. All other patients had the NPHS2 gene screened, and WT1 was tested in sporadic cases. In addition, 40 sporadic cases had the entire coding region of INF2 tested. Of the autosomal recessive and the sporadic cases, 13 and 6%, respectively, were found to have podocin-associated nephrotic syndrome, and 56% of them were compound heterozygous for the nonneutral p.R229Q polymorphism. Four percent of the sporadic and 10% of the autosomal dominant cases had a mutation in WT1. Pathogenic INF2 mutations were found in 20% of the dominant but none of the sporadic cases. In a large cohort of adolescents including both familial and sporadic disease, NPHS2 mutations explained about 7% and WT1 4% of cases, whereas INF2 proved relevant only in autosomal dominant familial disease. Thus, screening of the entire coding sequence of NPHS2 and exons 8-9 of WT1 appears to be the most rational and cost-effective screening approach in sporadic juvenile steroid-resistant nephrotic syndrome.

[Immunological parameters and ultrastructure of blood formed elements in nephrotic syndrome in children]

The aim of the study was the evaluation of significance of immunopathogenic mechanisms in the pathogenesis of minimal change nephrotic syndrome and the study of the ultrastructural changes of peripheral blood formed elements. The observation was carried out on 64 patients with steroid sensitive minimal change nephrotic syndrome. During the manifestation and recurrence of the disease, in the majority of the patients, the results of immunological studies revealed the reduction in both total and absolute count of T-lymphocytes on the background of decreased immunoregulatory index (T(4+)/ T(8+)). In the peripheral blood statistically reliable reduction in the percent value of T(3+) and T(4+) phenotype lymphocytes and elevation of number of T(8+)-lymphocytes were observed. On the background of normal values of B-lymphocytes appeared increase of IgM and decrease of IgG and IgA. In most cases significant elevation in the value of IgE - (244+10,3) and low values of INF-gamma, ultrastructural changes of blood monocytes were apparent. The peculiarities of ultrastructural changes of eosinophils and basophiles especially were pronounced by cytomembrane degranulation in form of decrease in electric density.