Clinical and histopathological characteristics of COL4A3 c.2881+1G>A variant causing Alport spectrum disorders in Croatian population.

Alport syndrome (AS) and thin basement membrane nephropathy (TBMN) are part of the spectrum of kidney disorders caused by pathogenic variants in α3, α4, or α5 chains of the collagen type IV, the major structural component of the glomerular basement membrane (GBM). Using targeted next-generation sequencing (NGS), 34 AS/TBMN patients (58.8% male) from 12 unrelated families were found positive for heterozygous c.2881+1G>A variant of the COL4A3gene, that is considered disease-causing. All patients were from the continental or island part of Croatia. Clinical, laboratory, and histopathological data collected from the medical records were analyzed and compared to understand the clinical course and prognosis of the affected patients. At the time of biopsy or first clinical evaluation, the mean age was 31 years (median: 35 years; range: 1 - 72 years). Hematuria was present in 33 patients (97.1%) and 19 (55.9%) patients had proteinuria. There were 6 (17.6%) patients with hearing loss, 4 (11.8%) with ocular lesions, and 11 (32.4%) with hypertension. Twenty-three (67.6%) patients had proteinuria at follow-up, and 5 (14.7%) patients with the median age of 48 years (range: 27-55) progressed to kidney failure, started dialysis, or underwent kidney transplantation. Of the 13 patients who underwent kidney biopsy, 4 (30.8%) developed focal segmental glomerulosclerosis (FSGS), and 8 (66.7%) showed lamellation of the GBM, including all patients with FSGS. It is essential to conduct a detailed analysis of each collagen type IV genetic variant to optimize the prognosis and therapeutic approach for affected patients.

Association of Generalized Psoriasis and Mixed Glomerulonephritis in a 10-year-old Girl.

Generalized psoriasis and renal function disorder were previously described in sporadic adult cases, revealing a new entity - psoriatic nephropathy. So far there have been only two cases describing this association in children. We present and discuss a case of 10-year-old girl with the unique biopsy findings of double glomerulonephritis associated with the simultaneous onset of generalized psoriasis.

Neurotoxicity of cyclosporine A in children with steroid-resistant nephrotic syndrome: is cytotoxic edema really an unfavorable predictor of permanent neurological damage?

BACKGROUND: Cyclosporine A-associated neurotoxicity has been reported mainly after organ transplantation. Only a small number of children with steroid-resistant nephrotic syndrome and cyclosporine A-associated neurotoxicity have been reported. PATIENTS: We report three children, aged 4, 11, and 15, with steroid-resistant nephrotic syndrome and cyclosporine A-associated neurotoxicity. In two of the patients, primary diagnosis was idiopathic nephrotic syndrome, and in one it was IgA nephropathy. Magnetic resonance with diffusion-weighted imaging, combined with quantification of apparent diffusion coefficient values, showed lesions caused by cytotoxic edema indicating irreversible brain damage. Nonetheless, the patients fully recovered clinically and radiologically after prompt discontinuation of cyclosporine A. CONCLUSIONS: Neurotoxic effects should be suspected in any child with nephrotic syndrome treated with cyclosporine A in whom sudden neurological symptoms occur. Cytotoxic edema is a rare finding in pediatric patients. However, even in such cases with seemingly irreversible brain damage, full recovery without permanent neurological sequels is possible with prompt cyclosporine A discontinuation and supportive therapy.

Calcium oxalate urolithiasis in children: urinary promoters/inhibitors and role of their ratios.

Diagnostic criteria for determination of inclination towards idiopathic calcium oxalate (CaOx) urolithiasis based on biochemical urine parameters are not sufficiently well defined in children. The aim of this study was to determine the risk of CaOx urolithiasis in children from concentrations of calcium, oxalate, citrate, and glycosaminoglycans in urine and their ratios, all standardized in respect to creatinine. We collected and analyzed 24-h urine samples of children with CaOx urolithiasis (n = 61) and compared with urine samples of matched control group of healthy children (n = 25). The study has showed that all stone formers have higher excretion of calcium (mmol/mmol creatinine), calcium/citrate (mol/mmol), and oxalate/(citrate × glycosaminoglycans) ratio (mol Ox × mol cr)/(mol Cit × g GAGs). ROC analysis of these variables gave criteria (>0.28, >1.07, and >0.08, respectively) for distinguishing stone formers from healthy children. Biochemical urine parameters and their ratios (calcium, calcium citrate, and oxalate/(citrate × glycosaminoglycans) enable one to discriminate idiopathic calcium oxalate stone formers from healthy children. Oxalate/(citrate × glycosaminoglycans) ratio per se can serve as an independent risk for stone formation. CONCLUSION: Using biochemical urine parameters and their ratios such as calcium, calcium/citrate, and oxalate/(citrate × glycosaminoglycans) enables one to determine diagnostic criteria towards idiopathic calcium oxalate urolithiasis in children. What is known: • The role of urine calcium as a promoter in calcium oxalate urolithiasis is well established. • Seldom used calcium/citrate ratio is acknowledged as a risk factor for calcium/oxalate urolithiasis. What is new: • The values of calcium and citrate in clinically and genetically proven idiopathic calcium oxalate urolithiasis make calcium/citrate ratio useful for diagnostic purposes in such stone formers. • Rarely used calcium independent oxalate/(citrate x glycosaminoglycans) ratio serves as the second best high specificity marker for idiopathic calcium oxalate urolithiasis.

Rational Therapy of Urinary Tract Infections in Children in Croatia

Resistance to chemotherapeutics used in the treatment of urinary tract infection is increasing throughout the world. Taking into account clinical experiences, as well as current bacterial resistance in Croatia and neighboring countries, the selection of antibiotic should be the optimal one. Treatment of urinary tract infection in children is particularly demanding due to their age and inclination to severe systemic reaction and renal scarring. If parenteral antibiotics are administered initially, it should be switched to oral medication as soon as possible. Financial aspects of antimicrobial therapy are also very important with the main goal to seek the optimal cost/benefit ratio. Financial orientation must appreciate the basic primum non nocere as a conditio sine qua non postulate as well.

Angiotensin-converting enzyme genotype is not a significant genetic risk factor for idiopathic nephrotic syndrome in Croatian children.

AIM: The association of the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with idiopathic nephrotic syndrome (INS) is controversial. Only scarce information on European populations is available. The aim of the study was to investigate the distribution of the ACE gene I/D polymorphism and its impact on INS in children from Croatia. MATERIALS AND METHODS: Ninety-five children with INS were investigated: 30 with minimal change disease (MCD), 35 with mesangial proliferative glomerulonephritis (MesPGN) and 30 with focal segmental glomerulosclerosis (FSGS). The control group consisted of 73 healthy adults. ACE gene was analyzed using the PCR method. The results were correlated with clinical features, renal morphology and response to immunosuppresive therapy. RESULTS: There was no correlation of ACE genotype with gender, age of the disease onset, level of proteinuria, presence of hematuria or hypertension, and GFR at onset of the disease. No statistically significant differences in ACE genotype or allele frequencies between the controls and whole group of patients, MCD group, MesPGN group, FSGS group, steroid sensitive (SS) patients, steroid resistant (SR) patients, as well as each other, were found, although DD genotype tended to be more frequent in FSGS patients, SR patients, and frequent relapsers. Among 11 children treated with cyclophosphamide the D allele was significantly higher among non-responders (p = 0.003). CONCLUSION: DD genotype is not a genetic risk factor for acquiring INS nor significant phenotype modifier regarding to clinical and pathohistological picture and response to steroids in Croatian children. The potential application of ACE genotyping in predicting cyclophosphamide response deserves further investigation.

[C1Q NEPHROPATHY: CASE REPORTS AND LITERATURE REVIEW]. / C1Q-NEFROPATIJA: PRIKAZI BOLESNIKA I PREGLED LITERATURE.

C1q nephropathy is considered a form of glomerulonephritis, defined by histological findings of dominant Clq immune deposits in renal biopsy. It is a rare disease, most often manifested in children and young adults. The most common clinical manifestation of the disease is nephrotic syndrome, but other renal syndromes could also be found. The cause of the disease is not known, but the immune pathogenesis could be assumed. Often, resistance to glucocorticoid or other immunosuppressive therapy is present, potentially leading to chronic renal insufficiency. We present ten patients with renal biopsy and clinical findings of Clq nephropathy. None of the patients had clinical or serological manifestations of systemic lupus. All patients had normal findings of C3 and C4 components of complement, as well as normal ANF, anti-dsD-NA and ANCA antibodies.

Renal thromboembolism during treatment with recombinant activated factor VII (rFVIIa) in a child with hemophilia B with factor IX inhibitors.

BACKGROUND: Serious thromboembolic events connected with rFVIIa therapy in hemophilia patients are rare. Only three cases are reported in children, all of them with hemophilia A. CASE PRESENTATION: We present unique case of patient with hemophilia B and high titer inhibitors to coagulation FIX, who developed severe renal damage due to thromboembolic event during rFVIIa therapy, associated with unsuspected renovascular anomalies. CONCLUSION: Caution is necessary if hematuria B requires administration of rFVIIa. US color doppler renal imaging before and after drug administration should be sufficient as an early warning.

Label-free mass spectrometric profiling of urinary proteins and metabolites from paediatric idiopathic nephrotic syndrome.

Idiopathic nephrotic syndrome (INS) is caused by renal diseases that increase the permeability of the glomerular filtration barrier without evidence of a specific systemic cause. The aim of the present work was to reveal inherent molecular features of INS in children using combined urinary proteomics and metabolomics profiling. In this study, label-free mass spectrometric analysis of urinary proteins and small molecule metabolites was carried out in 12 patients with INS versus 12 sex- and age-matched control subjects with normal renal function. Integration and biological interpretation of obtained results were carried out by Ingenuity IPA software. Validation of obtained proteomics data was carried out by Western blot method. Proteomics data have been deposited to the ProteomeXchange Consortium with the data set identifier PXD000765. This study indicates for the first time that paediatric INS is associated with up-regulation of afamin, hydroxyphenylacetate and uridine, and concomitant down-regulation in glutamine and phenylalanine levels, and many of these molecular species were previously shown to be involved in oxidative stress. Further studies in larger patient population are underway to investigate the role of oxidative stress in renal injury in paediatric INS.

Ultrasound distinction between simple recurrent urinary tract infections and a specific bladder wall inflammatory entity called cystitis cystica.

A specific representative of recurrent urinary tract infections (UTI) called cystitis cystica (CC) was assessed by ultrasound. The aim of the study was to delineate, by means of ultrasound measurement (US) of bladder wall thickness (BWT), the children with mere repeated UTI from those prone to frequent UTI due to CC. Two groups were compared, the control group of 30 with recurrent UTI without US CC BWT changes, and the group of 30 children with characteristic CC bladder wall thickening in whom cystoscopy was performed for verification the diagnosis of CC. BWT of > 3 mm (> 2.8 mm and > 3.3 mm) was found as cut-of value for distinction of CC versus simple recurrent UTI. US BWT measurement is useful in diagnosing CC and therefore valuable in decision about need of UTI prophylaxis.

Demographic characteristics and metabolic risk factors in Croatian children with urolithiasis.

The aim of this study was to assess demographic data, clinical presentation, metabolic features, and treatment in 76 children with urolithiasis presented from 2002 to 2011. Urolithiasis is responsible for 2.5/1,000 pediatric hospitalizations, with new cases diagnosed in 1.1/1,000 admissions. From the observed period, two-fold rise of incidence rate was observed. Compiling the data from other pediatric institutions in our country, we estimated present overall incidence rate in Croatia as 6.5/100,000 children under 18 years. There were 41 boys and 35 girls (ratio 1.17:1). The mean age at diagnosis was 9.7 (range 0.8-16) years and follow-up duration was 5.3 (range 1.8-10) years. Renal colic (75.0 %) and hematuria (57.89 %) were the main symptoms. In 65.78 % of children, stones were unilateral. Stones were located in kidney in 52.63 %, in the ureter in 26.32 %, and in bladder in 6.58 % cases. Stone analysis showed calcium oxalate in 75.0 % of the cases. Associated urinary tract abnormalities were found in 19.73 % children. Most common metabolic disturbances were hypercalciuria (47.37 %) and idiopathic or mild hyperoxaluria (18.42 %). Urine saturation (EQUIL2) was elevated in 61.84 % cases. Spontaneous stone evacuation occurred in 51.21 % children. Extracorporeal shock wave lithotripsy, surgical evacuation, and endoscopic removal of calculi were performed in 21.0, 6.58, and 5.26 % of cases, respectively. Follow-up conservative therapy, consisting of fluid/diet recommendations and additional potassium citrate and/or chlorothiazide in children with increased risk, was sufficient for stone recurrence prevention in 92.1 % of children. In conclusion, the study gave insight in epidemiology and metabolic disturbances of urinary stone disease in Croatian children.

Ultrasound bladder wall thickness measurement in diagnosis of recurrent urinary tract infections and cystitis cystica in prepubertal girls.

OBJECTIVE: To evaluate urinary bladder wall thickness (BWT) assessed by ultrasound as a diagnostic tool for cystitis cystica. PATIENTS AND METHODS: This was a 9-year prospective study comprising 120 prepubertal girls. Sixty subjects of whom half underwent cystoscopy represented cases while the other 60 (those with a single urinary tract infection and healthy subjects) represented controls. RESULTS: Based on receiver operating characteristics (ROC) analysis, BWT discriminated very well between cases and controls with area under the ROC curve close to 1.0. At the optimum cut-off defined at 3.9 mm, negative predictive value (NPV) was 100% leaving no probability of cystic cystitis with BWT <3.9 mm. Positive predictive value (PPV) was also very high (95.2%), indicating only around 4.82% probability of no cystic cystitis in patients with BWT values ≥3.9 mm. BWT could also distinguish between healthy subjects and those with a cured single urinary tract infection, although discriminatory properties were moderate (area under ROC 86.7%, PPV 78.8%, NPV 85.2%). CONCLUSION: Ultrasound mucosal bladder wall measurement is a non-invasive, simple and quite reliable method in diagnosis of cystitis cystica in prepubertal girls with recurrent urinary tract infections.

Childhood-onset systemic lupus erythematosus in Croatia: demographic, clinical and laboratory features, and factors influencing time to diagnosis.

OBJECTIVES: Childhood-onset systemic lupus erythematosus (cSLE) presents with diverse clinical features and often with non-classical symptoms that may delay diagnosis and increase risk of morbidity and mortality. This paper aims to analyse incidence, and clinical and laboratory features of cSLE in Croatia between 1991 and 2010, and to identify factors influencing time to diagnosis. RESULTS: Medical records at three university-based tertiary care centres were analysed retrospectively for 81 children with cSLE (68 girls). Mean age at onset was 13.4±2.8 yr (interquartile range 3), and annual incidence varied from 1-15 per million at risk. The most frequent clinical and laboratory features were musculoskeletal symptoms (80%) and increased erythrocyte sedimentation rate (96%). The most frequent immunological laboratory findings were the presence of antibodies against histones (86%), double-stranded DNA (73%), and Sm protein (64%), as well as low levels of C3 complement (69%). Haematuria was present in 58% of children, proteinuria in 56%, and biopsy-confirmed lupus nephritis in 43%. Median time from symptom onset to diagnosis was 2 months (range 0-96). Time to diagnosis was inversely associated with ECLAM score (p<0.001), but it showed no association with age, gender, clinical features or distance from the nearest paediatric centre. CONCLUSIONS: This is the first large-scale, in-depth study of clinical and laboratory features of cSLE in Croatia. Among all demographic, laboratory and clinical features examined, ECLAM score alone was inversely associated with time to diagnosis. This highlights the need to improve detection of children with fewer symptoms early in the course of the disease, therefore serious consequences for prognosis could be avoided.

Vesicoureteral reflux and urodynamic dysfunction.

INTRODUCTION: The concept of vesicoureteral reflux (VUR) as a consequence of congenital anomaly of vesicoureteral junction has undergone changes owing to the finding that such children may have lower urinary tract dysfunction, which produces high intravesical pressure and consequently a predisposition for VUR. PATIENTS AND METHODS: The urodynamics was investigated by pressure-flow-EMG study in 132 children with VUR and 162 refluxing units. RESULTS: Only 33 (25.0%) patients had normal urodynamic finding. The most frequent pathological finding was overactive bladder (OAB), found in 59 (44.7%) children, followed by dysfunctional voiding (DV) in 25 (18.9%) children. Children with VUR grades I and II had a higher percentage of pathological urodynamic findings than children with VUR grades III and IV. OAB was more frequent in children under 5 years of age with unilateral and lower grade VUR. It was found equally in children with and without uroinfections. DV was more frequent in children older than 5 years, with bilateral VUR, higher grade VUR and uroinfections. CONCLUSIONS: Children with VUR have a high incidence of urodynamic disorders. The results of the study indicate the possible role of urodynamic dysfunction in the pathogenesis of VUR, especially mild one.

Positive feedback loop for cystitis cystica: the effect of recurrent urinary tract infection on the number of bladder wall mucosa nodules.

The main purpose of this study was to demonstrate positive feedback loop between bladder wall nodules (nodules being one of the key diagnostic factors), bladder wall thickness, and recurrent urinary tract infections. Cystitis cystica was diagnosed in 115 prepubertal girls (mean age 7.79 +/- 3.05 years) by optic examination of bladder mucosal nodules and by ultrasonographic measurement of bladder wall thickness. Bladder wall thickness increased with the frequency of recurrent urinary tract infections as well as with the number of nodules on bladder wall mucosa (3.52 +/- 0.522 mm < or = 5 nodules vs. 4.42 +/- 0.429 mm 6-10 nodules vs. 5.20 +/- 0.610 mm > 10 nodules, respectively). Study results suggested that early control of urinary tract infections by chemoprophylaxis could prevent higher grades of bladder wall mucosal changes and consequently shorten the length of chemoprophylaxis.

Polyarteritis nodosa in Croatian children: a retrospective study over the last 20 years.

To analyze the disease characteristics, treatment modalities and outcome of polyarteritis nodosa (PAN) in Croatian children. Cross-sectional study included all children with PAN diagnosed according to EULAR/PRES/PRINTO criteria during the last two decades. PAN was diagnosed in 12 patients (6 girls and 6 boys) mean age (±SD) 11.33 ± 3.08 years. The share of PAN among all vasculitides was 3.8 %. Systemic PAN was diagnosed in 7 children (58 %), microscopic polyangiitis in 3 (25 %), cutaneous PAN in 2 (17 %). The most consistent symptoms were skin involvement (90 %) and arthritis/arthralgia (60 %). The CNS was affected in 33 % of patients. Inflammatory markers (C-reactive protein and erythrocyte sedimentation rate [ESR]) were elevated in all patients, and anti-neutrophil cytoplasmatic antibodies were positive in all patients with microscopic polyangiitis. Therapy mode for all patients was corticosteroids. Immunosuppressive drugs were used as additional therapy for patients with severe symptoms. Two patients (17 %), both suffering from microscopic polyangiitis, died due to renal failure during the follow-up. In comparison with available studies, we found a difference in distribution of childhood polyarteritis nodosa as well as some clinical characteristics (e.g., higher prevalence of neurological and pulmonary symptoms), while other researched features, laboratory and treatment were similar.

Idiopathic nephrotic syndrome in children: review of 282 Croatian cases.

Recent data suggests increased incidence of focal segmental glomerulosclerosis (FSGS) among children with idiopathic nephrotic syndrome (INS). To determine the causes and possible longitudinal changes in the etiology of INS, 282 Croatian children diagnosed with INS between 1990 and 2009 were evaluated. In total, 122 children were assessed as having minimal change nephrotic syndrome (MCNS) based on their initial presentation, laboratory findings and clinical course. Kidney biopsy was performed in the remaining 160 children. MCNS was present in 18.1% of all biopsies performed. Total incidence of MCNS (assessed + biopsy proven) was only 53.5%. In contrast, FSGS was found in 40.6% of all biopsies and accounted for 23.1% of all cases. Mesangial proliferative glomerulonephritis (MesPGN) was the third most common diagnosis, present in 26.9% of the biopsies, and accounted for 15.2% of all cases. There were no significant longitudinal differences in the incidence of different causes of INS. The overall response to steroids at presentation was 71.6%. A higher proportion of initial steroid responders among children with FSGS (43.1%) and MesPGN (67.4%) than previously reported was noted. A longitudinal tendency of increasing steroid resistance in FSGS and MesPGN groups was observed.

A boy with Dent-2 disease.

Dent-2 disease is an X-linked renal tubulopathy associated with mutations in OCRL gene. It is characterized by low-molecular weight proteinuria, hypercalciuria, nephrolithiasis/nephrocalcinosis and progressive renal failure. Patients may have some extra-renal symptoms of Lowe syndrome, such as peripheral cataracts, mental impairment, stunted growth or elevation of creatine kinase/lactate dehydrogenase. Our patient was suspected to suffer from Dent disease at 8 months of age because of proteinuria and hypercalciuria. He had no prominent extra-renal symptoms. OCRL mutation in exon 1 (c.217_218 del TT p.L73F, fs X1) was found. He was treated with amiloride+hydroclorthiazide and citrate with good results in reducing calciuria. His renal ultrasound, ophthalmologic and cardiologic examinations, mental development and other laboratory findings are normal till date.

Cystitis cystica and recurrent urinary tract infections in children.

The pathogenesis of recurrent urinary tract infections (UTIs) in preschool children with anatomically correct urinary tract (UT) is rather obscure. In girls, the bladder wall changes of cystitis cystica (CC) may be per se responsible for UTIs recurrence. During the 20-year period, 127 preschool children (125 girls; median age: 6.1 years) with CC, in whom UT anomalies were excluded, were diagnosed. The mean duration of UTIs symptoms prior to diagnosis was 3.31 +/- 2.51 years. Cystoscopical findings were labelled as mild, moderate and severe in 22.8%, 39.4% and 37.8% of patients, respectively. Following the confirmation of CC, long-term chemoprophylaxis with sulfamethoxazole-trimethoprim/nitrofurantoin was administered. A one year UTI-free period after chemoprophylaxis discontinuation was defined as therapeutic success. With 2.5 years median duration of regular chemoprophylaxis this goal was achieved in 58 children mainly with mild/ moderate CC. Thirty children from "improved/unchanged" group taking regular prophylaxis had significant reduction of UTIs ("improved"). Only 12 children belonging to the same group taking regular prophylaxis and all children with irregular prophylaxis had approximately the same number of UTIs as before treatment ("unchanged"). The "improved/unchanged" outcomes were predominantly found in children with severe form of CC. Although urodynamic disturbances detected in more than 50% of patients in whom urodynamics was performed were not found influential on the disease outcome, they could be responsible for its development. The results of our study suggest that regular and long-lasting chemoprophylaxis remains a basis for successful treatment for majority of patients with CC, even those with severe forms. If not treated properly with chemoprophylactic agents and without fair compliance in taking drugs, the disease is prone to recurrent UTIs.

[Clinical and histopathological characteristics of biopsy-proven renal diseases in Croatia]. / Klinicke i patohistoloske karakteristike biopsijom dokazanih bubreznih bolesti djece u Hrvatskoj.

There is little data on the spectrum of renal diseases in children in Croatia. The Croatian Society for Pediatric Nephrology has established the Registry of Biopsy-Proven Renal Diseases in an attempt to address this issue nationwide. Here we report preliminary results of a retrospective analysis of clinical and histopathological data of 565 children aged < or =17 years presenting to 9 hospitals in Croatia from 1991 to 2004, in whom kidney biopsy was performed. The most common indication for renal biopsy was nephrotic syndrome (39.1%), followed by asymptomatic proteinuria/hematuria (22.0%) and acute nephritic syndrome (17.0%). All biopsies were analysed by light-, immunofluorescent and electron microscopy. The majority of children, 552 out of 565 (92.4%), had glomerulonephritis (GN). Tubulointerstitial nephritis was found in 16 (2.8%), congenital renal parenchyma anomalies in 14 (2.5%) and vascular disease in 11 (1.9%) cases. One (0.2%) child had sarcoidosis with nephrocalcinosis. The sample was non-diagnostic in 1 (0.2%) case. Among children with GN, primary GN accounted for 70.9%, secondary GN for 16.1% and hereditary GN for 13.0% cases. The most frequent primary GN forms were focal segmental glomerulosclerosis (FSGS) (24.6%), mesangial proliferative glomerulonephritis (MEPGN) (19.2%) and IgA nephropathy (18.1%). Acute GN in resolution was found in 11.1% and minimal changes GN in 6.8% of cases. Most children with secondary GN had nephritis of Henoch-Schönlein purpura (HSP) (54.7%) and nephritis of systemic lupus erythematosus (SLE) (40.5%), while among hereditary GN Alport syndrome was most common (80.9%). In the group of children with primary GN who presented with nephrotic syndrome, most common forms were FSGS (38.5%) and MEPGN (24.0%). Minimal changes GN accounted for only 10.9% of cases. IgA nephropathy, primary or related to HSP (20.0%), FSGS (16.1%), MEPGN (12.6%) and Alport syndrome (9.7%) were the most common biopsy-proven renal diseases in Croatian children. The analysis provided data on the frequency of histological renal lesions in children in Croatia. The higher frequency of FSGS and MEPGN among Croatian children in comparison with other countries deserves further evaluation.