Next-generation sequencing in patients with familial FSGS: first report of collagen gene mutations in Tunisian patients.

Focal segmental glomerulosclerosis (FSGS) is a histological lesion with many causes, including inherited genetic defects, with significant proteinuria being the predominant clinical finding at presentation. FSGS is considered as a podocyte disease due to the fact that in the majority of patients with FSGS, the lesion results from defects in the podocyte structure. However, FSGS does not result exclusively from podocyte-associated genes. In this study, we used a genetic approach based on targeted next-generation sequencing (NGS) of 242 genes to identify the genetic cause of FSGS in seven Tunisian families. The sequencing results revealed the presence of eight distinct mutations including seven newly discovered ones: the c.538G>A (p.V180M) in NPHS2, c.5186G>A (p.R1729Q) in PLCE1 and c.232A>C (p.I78L) in PAX2 and five novel mutations in COL4A3 and COL4A4 genes. Four mutations (c.209G>A (p.G70D), c.725G>A (p.G242E), c.2225G>A (p.G742E), and c. 1681_1698del) were detected in COL4A3 gene and one mutation (c.1424G>A (p.G475D)) was found in COL4A4. In summary, NGS of a targeted gene panel is an ideal approach for the genetic testing of FSGS with multiple possible underlying etiologies. We have demonstrated that not only podocyte genes but also COL4A3/4 mutations should be considered in patients with FSGS.

Rituximab in The Management of Pediatric Steroid-Resistant Nephrotic Syndrome: A Systematic Review.

OBJECTIVES: To evaluate the efficacy and safety of rituximab in children with steroid-resistant nephrotic syndrome. STUDY DESIGN: A systematic review evaluating the efficacy and safety of rituximab in children with steroid-resistant nephrotic syndrome was performed. Data from studies, performed before April 2017 were collected, from MEDLINE, Cochrane Library, Scopus, and Web of Science. Study eligibility criteria included clinical trials and observational studies with a minimal sample size of 5 patients, regarding treatment with rituximab in children with steroid-resistant nephrotic syndrome. Independent extraction of articles by 2 investigators using predefined data fields was performed. RESULTS: We included 7 case series and 1 open-label randomized controlled trial. Among them, 3 studies were multicenter. A total of 226 patients were included. Mean age at onset was 5.6 ± 1.1 years. Mean number of rituximab administrations was 3.1 ± 1.1 infusions per patient. Remission was observed in 89 patients (46.4%). Remission was seen in 40.8% patients with initial steroid-resistant nephrotic syndrome and 52.8% patients with late steroid-resistant nephrotic syndrome. Good initial response to rituximab therapy was observed in 63.2% patients with minimal change nephrotic syndrome, 39.2% patients with focal and segmental glomerulosclerosis, 1 patient had diffuse mesangial hypercellularity, and 1 patient had IgM nephropathy. Sustained remission ranged from 18% to 93.7%. Five serious adverse events were observed. CONCLUSIONS: Rituximab exhibited a satisfactory profile regarding efficacy and safety indicating that this agent is a promising therapy for steroid-resistant nephrotic syndrome and should be further investigated by randomized clinical trials.

Identification of compound heterozygous patients with primary hyperoxaluria type 1: clinical evaluations and in silico investigations.

BACKGROUND: Primary hyperoxaluria type 1 (PH1) is an autosomal recessive inherited disorder of glyoxylate metabolism in which excessive oxalates are formed by the liver and excreted by the kidneys. Calcium oxalate crystallizes in the urine, leading to urolithiasis, nephrocalcinosis, and consequent renal failure if treatment is not initiated promptly. Mutations in the AGXT gene which encodes the hepatic peroxisomal enzyme alanine:glyoxylate aminotransferase are responsible of PH1. In the present work, we aimed to analyze AGXT gene and in silico investigations performed in four patients with PH1 among two non consanguineous families. METHODS: Exhaustive gene sequencing was performed after PCR amplification of coding exons and introns boundaries. Bioinformatic tools were used to predict the impact of AGXT variants on gene expression as well as on the protein structure and function. RESULTS: Direct sequencing of all exons of AGXT gene revealed the emergence of multiple mutations in compound heterozygous state in the two studied families. Two patients were compound heterozygous for the c.731 T > C, c.32C > T, c.1020A > G and c.33_34insC and presented clinically with recurrent urinary tract infection, multiple urolithiasis and nephrocalcinosis under the age of 1 year and a persistent hyperoxaluria at the age of diagnosis. The two other patients presenting a less severe phenotypes were heterozygous for c.731 T > C and homozygous for the c.32C > T and c.1020A > G or compound heterozygous for c.26C > A and c.65A > G variants. CONCLUSION: In Summary, we provided relevance regarding the compound heterozygous mutations in non consanguineous PH1 families with variable severity.

Neonatal lupus erythematosus with congenital heart block in twins.

Background - Neonatal lupus erythematosus is an uncommon acquired autoimmune disease caused by transplacental passage of maternal antibodies SSA/Ro, SSB/La or U1 ribonucleoproteins. The most common clinical manifestations are skin rash, cardiac lesions, thrombocytopenia, anemia and hepatosplenomegaly. Complete congenital heart block is usually irreversible needing a pacemaker implantation in two-thirds of cases. Cases report - We report neonatal lupus erythematosus with complete congenital heart block in twins. Newborns were delivered by caesarean section at week 38 of gestation with a heart rate regular at 70 beats per minute. Both twins and mother were positive for antinuclear, anti-SSA, and anti-SSB antibodies. Twins received single-chamber pacemaker implants at day 12 of life. The evolution was immediately favorable with a heart rate around 110 beats per minute. The follow-up was 2 years. The twins are currently asymptomatic. Conclusion - Complete congenital heart block is the most serious manifestation of the neonatal lupus erythematosus associated with significant morbidity and mortality.

Genetic insights into fetal kidney development: Variants in HNF1A and PKHD1 genes.

The orchestration of fetal kidney development involves the precise control of numerous genes, including HNF1A, HNF1B and PKHD1. Understanding the genetic factors influencing fetal kidney development is essential for unraveling the complexities of renal disorders. This study aimed to search for disease-causing variants in HNF1A, HNF1B, PKHD1 genes, among fetus and babies or via parental samples, using sanger sequencing, NGS technologie and MLPA. The study revealed an absence of gene deletions and disease-causing variants in the HNF1B gene. However, five previously SNPs in the HNF1A gene were identified in four patients (patients 1, 2, 3, and 4). These include c.51C > G (Exon1, p. Leu17=), c.79A > C (Exon1, p. Ile27Leu), c.1375C > T (Exon7, p. Leu459=), c.1460G > A (Exon7, p. Ser487Asn), and c.1501 + 7G > A (Intron7). Additionally, in addition to previously SNPs identified, a de novo heterozygous missense mutation (p.E508K) was detected in patient 4. Furthermore, a heterozygous mutation in exon 16 (p. Arg494*; c.1480C > T) was identified in both parents of patient 5, allowing predictions of fetal homozygosity. Bioinformatic analyses predicted the effects of the c.1522G > A mutation (p.E508K) on splicing processes, pre-mRNA structures, and protein instability and conformation. Similarly, the c.1480C > T mutation (p. Arg494*) was predicted to introduce a premature codon stop, leads to the production of a shorter protein with altered or impaired function. Identification of variants in the HNF1A and in PKHD1 genes provides valuable insights into the genetic landscape of renal abnormalities in affected patients. These findings underscore the heterogeneity of genetic variants contributing to renal disorders and emphasize the importance of genetic screening.

Mechanical complications of peritoneal dialysis in Tunisian children.

INTRODUCTION: Peritoneal dialysis (PD) is the method of choice for extra-renal replacement therapy (ERT) for children with end-stage renal disease (ESRD), because of its various advantages. However, it presents different infectious and non-infectious complications, causes of important morbidity and mortality. AIM: To determine the mechanical complications of PD in our center and to identify risk factors of their occurrence. METHODS: We retrospectively collected the records of 99 patients who were treated with PD within the past eleven years in the department of pediatrics of the University Hospital Charles Nicolle of Tunis. Analysis examining possible risque factors were performed using parametric and non-parametric tests. RESULTS: A total of 63 patients had mechanical complications with an incidence of peritoneal dialysis catheter revision of 1 procedure every 38 months. The causes were dominated by catheter migration (27.5%) and obstruction by fibrin or blood clotting (19.8%). A history of peritonitis (p=0.046) and the presence of comorbidity (p=0.008) were the two independent risk factors for catheter revision. Inguinal hernia was noted in six patients. No patient presented with a hydrothorax. Seven patients presented an episode of hemoperitoneum. CONCLUSION: Our results lead us to focus our efforts on preventing peritonitis and controlling morbidity. Prospective studies will enable us to confirm our results.

Lupus Nephritis in Tunisian Children: Predictive Factors of Poor Outcomes.

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder of unknown etiology. Lupus nephritis (LN) is one of the most severe clinical manifestations observed in patients with SLE; it is more frequent and more severe in children than in adults. The aim of our study was to assess the predictive factors of poor outcomes in Tunisian children with LN. This was a multicenter retrospective observational study on 40 pediatric patients with biopsy-proven LN from five nephrology departments in Tunisia. The patients were 12.33 ± 3.3 years of age at the time of their kidney biopsy. Eleven patients developed end-stage renal disease (ESRD) (27.5%), and seven patients died. Overall, 18 (45%) patients reached our composite endpoint (ESRD or death). An age at diagnosis of more than 14 years, elevated serum creatinine at the time of the kidney biopsy, the existence of wire loops, thromboembolic complications as well as infectious complications are the most important clinical features associated with an increased risk of ESRD. Predictive factors of death were a baseline creatinine level of more than 2.26 mg/dL, a high proteinuria at baseline, fibrous crescents determined by renal biopsy, thromboembolic complications, infectious compli-cations, and ESRD. In summary, our results suggest that early and appropriate management is the best guarantee of a good renal outcome in children with LN.

Custom Next-Generation Sequencing Identifies Novel Mutations Expanding the Molecular and clinical spectrum of isolated Hearing Impairment or along with defects of the retina, the thyroid, and the kidneys.

BACKGROUND: In the Tunisian population, the molecular analysis of hearing impairment remains based on conventional approaches, which makes the task laborious and enormously expensive. Exploration of the etiology of Hearing Impairment and the early diagnosis of causal mutations by next-generation sequencing help significantly alleviate social and economic problems. METHODS: We elaborated a custom SureSelectQXT panel for next-generation sequencing of the coding sequences of 42 genes involved in isolated hearing impairment or along with defects of the retina, the thyroid, and the kidneys. RESULTS: We report eight pathogenic variants, four of which are novel in patients with isolated hearing impairment, hearing impairment, and renal tubular acidosis, Usher syndrome and Pendred syndrome. Functional studies using molecular modeling showed the severe impact of the novel missense mutations on the concerned proteins. Basically, we identified mutations in nuclear as well as mitochondrial genes in a Tunisian family with isolated hearing impairment, which explains definitely the phenotype detected since 2006. CONCLUSION: Our results expanded the mutation spectrum and genotype-phenotype correlation of isolated and syndromic hearing loss and also emphasized the importance of combining both targeted next-generation sequencing and detailed clinical evaluation to elaborate a more accurate diagnosis for hearing impairment and related phenotypes especially in North African populations.

[Post-streptococcal glomerulonephritis in the south of Tunisia: A 12-year retrospective review]. / La glomérulonéphrite aiguë post-streptococcique de l'enfant dans le sud tunisien : étude rétrospective de 12 ans.

AIM: Post-streptococcal glomerulonephritis (PSGN) is a frequent cause of acute nephritis in children. This study aimed to describe the epidemiology, clinical characteristics and outcomes of PSGN and look for predictor's factors of severity. METHODS: A 12-year retrospective review of case notes and laboratory data was conducted at a department of pediatrics, pediatric emergency and intensive care, Hedi Chaker Hospital. RESULTS: One hundred seventy eight children were treated for PSGN with a mean age of 7.6 ans±3.43 ans. One hundred and forty-two patients (80%) had a history of a recent upper respiratory tract or skin infection. Streptococcal pharyngitis was the most common cause, identified in 113 patients (67.6%). Macroscopic hematuria and edema were noted in 135 (75.8%) and 114 cases (64%) respectively. Hypertension was present in 55 patients (31%). Oliguria was noted in 30 children (16.8%). Sixty-six subjects (37%) developed acute renal impairment (creatinine≥70 micromoles/L). No correlation was demonstrated between acute renal impairment and age, sex, triggering infection, anemia and white blood cell count. Creatinine greater than 56.35 micromoles/L was associated with a high risk of developing high blood pressure. The mean length of admission was 5.8 days±4.44. Only one subject has ongoing renal dysfunction. CONCLUSION: PSGN remains a common nephropathy in our region. The detection and effective treatment of any infection that may be involved can reduce the incidence of this disease.

[Etiologies of end-stage renal disease of children in Tunisia]. / Épidémiologie de l'insuffisance rénale terminale de l'enfant en Tunisie.

BACKGROUND: The end-stage renal disease (ESRD) in children has special features in terms of etiologies, therapeutic modalities and access to renal transplantation. In Tunisia, there are no data on the epidemiology of ESRD in children. The aim of our study was to describe epidemiology of ESRD among Tunisian children. METHODS: This retrospective study was conducted in pediatric departments in Charles-Nicolle Hospital, Tunis and Hedi Chaker hospital, Sfax, during a period of 15 years (1st January 1998-31st December 2013). We included children who develop ESRD before the age of 15 years. RESULTS: In total, 166 patients were included. The median duration of follow-up was 48 months. We collected respectively 24 children (14.5%) aged less than 2 years, 24 children (14.5%) aged between 2 and 6 years and 118 children (71%) older than 6 years. The sex ratio was equal to 1.4. The mean incidence was 4.25 cases per million children. The main causes were represented by congenital anomalies of the kidneys and urinary tract (35.5%), hereditary renal disease (31.3%) and glomerular kidney disease (9.6%). All patients were treated in kidney transplant dialysis programs; the main mode of dialysis was represented by peritoneal dialysis, which represented the initial dialysis mode in 81% of cases. The transition to hemodialysis was noted in 43.4% cases. Thirty-eight patients (22.8%) were transplanted. The mortality rate was 27.1%. The leading cause of death was cardiovascular diseases (37.7%) and infections (22.2%). CONCLUSION: The creation of a national registry of kidney disease in Tunisia is necessary for a better knowledge of needs for dialysis and renal transplantation in children.

Cholestasis and protein-losing enteropathy secondary to hyperthyroidism in a 6-year-old girl.

Hepatic dysfunctions are not infrequent in patients with hyperthyroidism. These disorders may be related to the effects of the excess thyroid hormone secretion, to the uses of antithyroid drugs, or to the presence of concomitant hepatic diseases. Our aim is to describe the clinical and biochemical features of liver dysfunction related to thyrotoxicosis. We report here a case of a 6-year-old girl who was admitted for jaundice and pruritus as a result of the development of hyperthyroidism due to Graves' disease. On physical examination at admission, she was found to have jaundice and hepatomegaly. Laboratory data show cholestasis and protein-losing enteropathy. Investigations exclude other causes of hepatic disorder. One month after the initiation of antithyroid drug, the patient became euthyroid with improvement in jaundice and pruritus and normalization of hepatic tests and alpha antitrypsine clearance. In conclusion, the diagnosis of hyperthyroidism may be delayed in patients in whom the primary manifestations were pruritus and jaundice. The physician should suspect thyrotoxicosis prior to hepatitis or skin manifestations.