Although asymptomatic bacteriuria, cystitis, and acute pyelonephritis (APN) have been categorized as urinary tract infections (UTIs), the immunopathogenesis of each disease is different. APN shows an age predilection; the majority of children (over 70-80%) with APN are under 1-2 years of age, with a male predominance. After 1-2 years of age, female predominance has been reported. This finding suggests that the immature immune state of infancy may be associated with the pathogenesis of APN. Escherichia coli is the most common etiologic agent; other uropathogens associated with UTIs originate from the host and comprise normal flora that are continuously altered by environmental factors. Therefore, uropathogens may have characteristics different from those of extraneous bacterial pathogens. Although antibiotic-resistant uropathogens, including extended-spectrum beta-lactamase-producing strains, are increasing in Korea and worldwide, treatment failure is rare in immune-competent children. The immunopathogenesis of APN remains unknown. Intact bacteria may not be the causative substances in renal cell injury; rather, smaller substances produced during bacterial replication may be responsible for renal cell injury and scarring. Moreover, substances from host cells such as proinflammatory cytokines may be involved in renal cell injury. A dimercaptosuccinic acid scan is used to detect the site of bacterial replication in the renal parenchyma, and may be influenced by the size of the focus and the stage of APN. Traditional aggressive studies used to identify vesicoureteral reflux after the first episode of APN have been modified because of rare cases of chronic kidney disease in patients with recurrent UTI.

Purpose: This study was performed to evaluate the effects of cyclosporine-A (CsA) on linear growth in pediatric patients with steroid-dependent (SDNS) or resistant nephrotic syndrome (SRNS). Methods: Thirty-five pediatric patients with SDNS or SRNS undergoing glucocorticoid (GC) and/or CsA treatment were retrospectively reviewed. Seventeen patients were treated with GC alone and 18 were treated with GC and CsA. The cumulative doses of GC and CsA were quantified (mg/kg/day). Linear growth during the follow-up period was defined as the difference in Z-score between the initial and final height according to the follow-up period (${\Delta}$ height Z score/year). The associations between linear growth and clinical parameters were analyzed. Results: The linear growth of patients in the two groups was not significantly different (P=0.262). The ${\Delta}$ height Z score/year did not show a significant correlation with the cumulative doses of CsA, but was negatively correlated with the cumulative dose of GC and positively correlated with the Z score for height at the time of diagnosis. Conclusion: In children with SDNS or SRNS undergoing GC therapy, added CsA treatment may not have harmful effects on linear growth.

Purpose: Nocturnal enuresis (NE) is one of the most common problems in childhood. NE has a multifactorial etiology and is influenced by sleep and arousal mechanisms. The aim of the present study was to prospectively evaluate sleep problems and patterns in children with NE compared with normal healthy controls. Methods: Twenty-eight children with NE and 16 healthy controls were included in the study. To evaluate sleep habits and disturbances, parents and children filled out a questionnaire that included items about sleep patterns and sleep-related behaviors prior to treatment for NE. Demographic factors and other data were compared for the two groups based on the responses to the sleep questionnaire. Results: Night awakening, sleepwalking, and periodic limb movements were more prevalent in children with NE, but symptoms of sleep-disordered breathing were not increased in this group. There were statistically significant differences in periodic limb movements and daytime sleepiness between the two groups. Conclusion: Children with NE seemed to have more sleep problems such as night awakening, sleepwalking, and periodic limb movements. In addition, a higher level of daytime sleepiness and hyperactivity in patients with NE suggested a relationship between NE and sleep disorders.

Purpose: We used technetium-99m dimercaptosuccinic acid (DMSA) scintigraphy to identify factors predictive of renal cortical defects in infants <3 months of age with urinary tract infections (UTIs). Methods: We retrospectively reviewed data on infants <3 months of age with culture-proven UTIs treated at a single center from March 2010 to February 2016. Blood samples were obtained for laboratory evaluation prior to commencement of antibiotic therapy. The therapeutic delay time (TDT) and therapeutic response time (TRT) were recorded. All patients were divided into two groups depending on features of their DMSA scans. We compared the demographic, clinical, and laboratory characteristics of the two groups. Results: A total of 119 infants (94 males and 25 females; mean age, $56.9{\pm}21.3days$) were included. Cortical defects were evident in the DMSA scans of 47 cases (39.5%). In infants with such defects, the peak temperatures ($38.9{\pm}0.57^{\circ}C$ vs. $38.4{\pm}0.81^{\circ}C$, P=0.001), the absolute neutrophil counts ($8,920{\pm}4,460/mm$ vs. $7,290{\pm}4,090/mm$, P=0.043), and the C-reactive protein (CRP) levels ($6.49{\pm}4.33mg/dL$ vs. $3.21{\pm}2.81mg/dL$, P=0.001) were significantly higher than those in infants without cortical defects. The TDT was also longer in those with cortical defects (P=0.037). Conclusion: We found that a TDT ${\geq}8.5hr$ (odds ratio [OR] 5.81), a peak temperature ${\geq}38.3^{\circ}C$ (OR 6.19), and a CRP level ${\geq}4.96mg/dL$ (OR 7.26) predicted abnormal DMSA scan results in infants <3 months of age with UTIs.

Purpose: Disruption of normal renal development can lead to congenital anomalies of the kidney and urinary tract, including renal hypodysplasia. We aimed to clarify whether small kidney size affects clinical manifestations in children with urinary tract infection (UTI). Methods: One hundred fifty-four patients who had their first symptomatic UTI between January 2014 and June 2015 were enrolled in this study. Differences in kidney size were estimated based on percent uptake of $^{99m}Tc-$ dimercaptosuccinic acid (DMSA) in scintigraphy. The patients who showed more than 10% difference in kidney size on DMSA scintigraphy with none or minimal cortical defects were included in group A. (group A, n=17). Laboratory, clinical, and imaging results were compared with those of the other patients (group B, n=137). Results: Group A had a relatively higher incidence of vesicoureteral reflux than group B (44% vs 20%, P<0.05). The levels of plasma neutrophil gelatinase-associated lipocalin (NGAL) and serum C-reactive protein were significantly higher in group A (193 [64-337] vs 91 [59-211] ng/mL and 4.1 [0.5-11.9] vs 2.1 [0.7-5.3] ng/mL, respectively; all P <0.05). Linear regression analysis revealed that plasma NGAL level strongly correlated with the difference in renal uptake in DMSA scintigraphy in group A ($R^2=0.505$). Conclusion: The difference in kidney size could influence the clinical course and severity of pediatric UTI.

Purpose: The aim of this study was to compare the clinical and laboratory features of infants with roseola infantum due to human herpesvirus 6 (HHV6) infection and those with urinary tract infection (UTI). Methods: We retrospectively reviewed the medical records of children who were hospitalized at Cheil General Hospital and Women's Health Care Center, College of Medicine, Dankook University, and diagnosed as having HHV6 infection or UTI. Results: Among the infants admitted between September 2014 and May 2016, 92 (male, 45 and female, 47) were included in the study and divided into a HHV6 infection group (n=50) and a UTI group (n=42). The relative risk of UTI compared with that of HHV6 infection increased with pyuria (P<0.001), increased with leukocytosis (mean white blood cell [WBC] count, $15,048{\pm}5,756/mm^3$ vs $87,916{\pm}54,056/mm^3$; P<0.001), increased with C-reactive protein (CRP) level ($4.89{\pm}4.85 mg/dL$ vs $1.04{\pm}1.76mg/dL$; P<0.001), and younger age ($6.3{\pm}3.2months$ vs $18.3{\pm}12.6months$; P<0.001). The relative risk of HHV6 infection compared with that of UTI increased with fever duration ($4.3{\pm}1.7days$ vs $2.8{\pm}1.7days$; P<0.001) and decreased with platelet (PLT) count ($373{\pm}94{\times}10^3/mm^3$ vs $229{\pm}90{\times}10^3/mm^3$; P<0.001). No significant differences were found between the HHV6 groups according to the presence or absence of pyuria. Conclusion: Pyuria, age, fever duration, WBC count, CRP level, and PLT count were the differentiating factors of HHV6 infection from UTI. However, sterile pyuria can occur in children with HHV6 infection. In the presence of pyuria, CRP level and PLT count were the strong predictors of UTI compared with HHV6.

Purpose: Early diagnosis and treatment of urinary tract infection have been emphasized to prevent renal scarring. If untreated, acute pyelonephritis could cause renal injury, which leads to renal scarring, hypertension, proteinuria, and chronic renal failure. The purpose of this study was to assess risk factors of renal scarring after treatment of acute pyelonephritis (APN). Methods: The medical records of 59 patients admitted at Daegu Fatima Hospital because of APN between March 2008 and April 2015 whose renal cortical defects were confirmed by using initial technetium-99m dimercaptosuccinic acid (DMSA) scans were reviewed retrospectively. We divided 59 patients into 2 groups according to the presence of renal scar and assessed risk factors of renal scar, including sex, age at diagnosis, feeding method, hydronephrosis, bacterial species, vesicoureteral reflux, and vesicoureteral reflux grade. Results: Of 59 patients (41%), 24 showed renal scar on follow-up DMSA scan. No significant differences in sex, hydronephrosis, bacterial species, and fever duration were found between the renal-scarred and non-scarred groups. As for age at diagnosis, age of >12 months had 5.8 times higher incidence rate of renal scarring. Vesicoureteral reflux (VUR) affected renal scar formation. VUR grade III or IV had 14.7 times greater influence on renal scar formation than VUR grade I or II. Conclusion: Our data suggest that the presence of VUR and its grade and age at diagnosis are risk factors of renal scar on follow-up DMSA scan after APN.

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency of the enzyme ${\alpha}-galactosidase$ A, resulting in the accumulation of glycosphingolipids within the lysosomes of various cell types. It has a wide spectrum of clinical phenotypes, and renal failure is a serious complication. Fabry disease is confirmed either by measurement of ${\alpha}-galactosidase$ A activity or by genetic testing for GLA mutations. Renal biopsy findings on light microscopy, specifically enlarged podocytes with foamy cytoplasm, and osmiophilic inclusion bodies in the cytoplasm in all types of renal cells on electron microscopy, are characteristic of this disease. The predominant differential diagnosis is iatrogenic phospholipidosis in association with certain drugs that can cause cellular injuries indistinguishable from Fabry disease. Here, we report the case of a 10-year-old boy with microscopic hematuria who underwent a renal biopsy that showed morphological findings consistent with Fabry disease, although the patient had neither a GLA mutation nor a history of drug consumption. Six years later, spontaneous regression of this renal pathology was observed in a second renal biopsy examination.

Congenital chloride diarrhea (CLD) is a rare autosomal recessive disease that is difficult to diagnose. CLD requires early treatment to correct electrolyte imbalance and alkalosis and to prevent severe dehydration. Renal injury is clearly associated with defective electrolyte balance induced by CLD, particularly during the first months or years of life. A 7-year-old boy was diagnosed with CLD following detection of a homozygous mutation (c.2063-1G>T) in SLC26A3 at 6 months of age. During treatment with electrolyte supplements, mild proteinuria was detected at 8 months of age, and is still present. Renal biopsy showed the presence of focal renal dysplasia, with metaplastic cartilage and mononuclear cell infiltration, calcification, and fibrosis in the interstitium. Up to two-thirds of the glomeruli exhibited global obsolescence, mostly aggregated in the dysplastic area. In nondysplastic areas, the glomeruli were markedly increased in size and severely hypercellular, with increased mesangial matrix, and displayed segmental sclerosis. The marked glomerular hypertrophy with focal segmental glomerulosclerosis suggested a compensatory reaction to the severe nephron loss or glomerular obsolescence associated with renal dysplasia, with superimposed by CLD aggravating the tubulointerstitial damage.

Nephrogenic diabetes insipidus (NDI) can cause nonobstructive hydronephrosis. Congenital NDI (CNDI) is caused by a genetic mutation. This case report presents a 12-year-old girl who was incidentally diagnosed with nonobstructive hydronephrosis due to NDI caused by AQP2 gene mutation after being evaluated for microscopic hematuria found on routine health examination at school. The patient's medical and family history was unremarkable, and she complained of nocturia only at the time of the clinic visit. Bilateral hydronephrosis on abdominal ultrasonography prompted a water deprivation test, leading to diagnosis of NDI. Genetic study confirmed p.Asn (AAC)123Ser (AGC) in exon 2 of the AQP2 gene. Polyuria and hydronephrosis improved following arginine-vasopressin therapy. CNDI responsive to treatment should be considered as a possible cause of nonobstructive hydroureter.

Henoch-$Sch{\ddot{o}}nlein$ purpura (HSP) is the most common vasculitis in children, mainly affecting the small vessels of the skin, joints, gastrointestinal tract, and kidneys. Although most cases of HSP resolve spontaneously without sequelae, serious nephrological and intestinal problems may occur in some cases. We experienced a case of HSP complicated by simultaneous intussusception and nephritis in a 14-year-old boy who developed a sudden abdominal pain and gross hematuria on the 11th day after onset of the disease. Imaging studies revealed intussusception that required emergency laparotomy. Despite treatment with steroid and angiotensin-converting enzyme inhibitors, nephritis and nephrosis progressed for 4 weeks, and renal biopsy was performed to confirm the diagnosis. Cyclosporin A therapy was started, and remission of proteinuria was achieved after 5 months. However, the nephritis recurred and worsened to end-stage renal failure during 15 years of follow-up.

Toxic epidermal necrolysis (TEN) is a rare, acute, serious, and potentially fatal skin disease, in which cell death causes the epidermis to separate from the dermis. It is thought to be a hypersensitivity complex that affects the skin and mucous membranes, and is caused by certain medications, infections, genetic factors, underlying immunologic disease, or more rarely, cancers. We report two cases of TEN associated with deflazacort (DFZ), a derivative of prednisolone, used in the first episode of nephrotic syndrome (NS). The skin eruption appeared on the $4^{th}$ and $5^{th}$ weeks after DFZ administration, while NS was in remission. The widespread lesions were managed by intensive supportive treatment, discontinuation of DFZ, and oral administration of cyclosporine. Both patients showed a rapid improvement in symptoms of TEN without any complications or relapse of NS.