Associations between Urinary Mercury/Cadmium Concentrations and Anthropometric Features in Korean Children.

Investigating the impact of urinary mercury and cadmium on anthropometric parameters in Korean children is crucial amid growing concerns about heavy metal exposure and childhood growth. Using data from the Korean National Environmental Health Survey (2015-2017), we assessed age- and sex-specific associations of urinary mercury and cadmium with height and body mass index (BMI) z-scores in 1458 children aged 3-5 (n = 571) and 6-11 years (n = 887). Overall, 5.0% had stunted height (3-5 years: 6.9%, 6-11 years: 3.8%), whereas older children exhibited higher overweight/obesity prevalence (29.2%) than younger ones did (22.2%). In 3-5-year-old boys, urinary mercury correlated negatively with height z-scores (p < 0.001), whereas in girls, urinary cadmium correlated positively (p = 0.015). Boys aged 6-11 years showed positive associations between mercury/cadmium levels and BMI z-scores (p = 0.012). Logistic regression indicated associations between urinary mercury and stunted height likelihood (p = 0.001) and between urinary cadmium and reduced overweight likelihood (p = 0.039) in 3-5-year-old boys. In boys aged 6-11 years, urinary cadmium levels were positively associated with overweight likelihood (p = 0.003). This study underscores the link between elevated urinary mercury, cadmium levels, and growth disruptions in Korean children, emphasizing the need for public health strategies for reducing childhood heavy metal exposure.

CellNeighborEX: deciphering neighbor-dependent gene expression from spatial transcriptomics data.

Cells have evolved their communication methods to sense their microenvironments and send biological signals. In addition to communication using ligands and receptors, cells use diverse channels including gap junctions to communicate with their immediate neighbors. Current approaches, however, cannot effectively capture the influence of various microenvironments. Here, we propose a novel approach to investigate cell neighbor-dependent gene expression (CellNeighborEX) in spatial transcriptomics (ST) data. To categorize cells based on their microenvironment, CellNeighborEX uses direct cell location or the mixture of transcriptome from multiple cells depending on ST technologies. For each cell type, CellNeighborEX identifies diverse gene sets associated with partnering cell types, providing further insight. We found that cells express different genes depending on their neighboring cell types in various tissues including mouse embryos, brain, and liver cancer. Those genes are associated with critical biological processes such as development or metastases. We further validated that gene expression is induced by neighboring partners via spatial visualization. The neighbor-dependent gene expression suggests new potential genes involved in cell-cell interactions beyond what ligand-receptor co-expression can discover.

KAAACI Allergic Rhinitis Guidelines: Part 2. Update in Non-pharmacological Management.

Allergic rhinitis is the most common chronic disease worldwide. Various upper airway symptoms lower quality of life, and due to the recurrent symptoms, multiple treatments are usually attempted rather than one definitive treatment. There are alternatives to medical (medication-based) and non-medical treatments. A guideline is needed to understand allergic rhinitis and develop an appropriate treatment plan. We have developed guidelines for medical treatment based on previous reports. The current guidelines herein are associated with the "KAAACI Evidence-Based Guidelines for Allergic Rhinitis in Korea, Part 1: Update in pharmacotherapy" in which we aimed to provide evidence-based recommendations for the medical treatment of allergic rhinitis. Part 2 focuses on non-pharmacological management, including allergen-specific immunotherapy, subcutaneous or sublingual immunotherapy, nasal saline irrigation, environmental management strategies, companion animal management, and nasal turbinate surgery. The evidence to support the treatment efficacy, safety, and selection has been systematically reviewed. However, larger controlled studies are needed to elevate the level of evidence to select rational non-medical therapeutic options for patients with allergic rhinitis.

Efficacy of Seven-Day Potassium-Competitive Acid Blocker-Based First-Line Helicobacter Pylori Eradication Therapy Administered with Bismuth.

PURPOSE: To determine the efficacy of a potassium-competitive acid blocker (P-CAB)-based first-line eradication therapy with bismuth compared with that of proton pump inhibitor-based first-line therapy with bismuth. MATERIALS AND METHODS: Eradication-naive H. pylori-infected patients were consecutively enrolled from January to November 2020. Before approval of the P-CAB-based eradication therapy, twice daily administration of a regimen containing lansoprazole 30 mg, amoxicillin 1 g, clarithromycin 500 mg, and bismuth potassium citrate 300 mg was prescribed for 7 days. After approval, lansoprazole was replaced with tegoprazan (50 mg). Clarithromycin resistance was examined in patients who underwent gastroscopic biopsy at our center. Efficacy was assessed via the 13C-urea breath test. RESULTS: Of the 381 eradication-naive patients, eradication was successful in 88.3% (151/171) treated with tegoprazan and 82.8% (140/169) treated with lansoprazole in per-protocol analysis (p=0.151). In intention-to-treat analysis, eradication rates were 78.8% (152/193) in the tegoprazan and 74.5% (140/188) in the lansoprazole group (p=0.323). Clarithromycin resistance was observed in 30 (20.1%) of the 148 patients (74 from each group), and only four of the 16 clarithromycin-resistant patients in the tegoprazan group achieved successful eradication. Clarithromycin resistance [odds ratio (OR)=42.1, 95% confidence intervals (CIs)=12.6-141.0] and poor patient compliance (OR=17.1, 95% CIs=1.6-189.1) were independent risk factors for eradication failure. CONCLUSION: In eradication-naive patients, eradication success rates for 7-day first-line triple therapy regimen exceeded 82% with bismuth administration. In clarithromycin-resistant patients, neither tegoprazan 50 mg nor lansoprazole 30 mg achieved acceptable eradication rates when administered twice daily for 7 days.

Basement membrane stiffness determines metastases formation.

The basement membrane (BM) is a special type of extracellular matrix and presents the major barrier cancer cells have to overcome multiple times to form metastases. Here we show that BM stiffness is a major determinant of metastases formation in several tissues and identify netrin-4 (Net4) as a key regulator of BM stiffness. Mechanistically, our biophysical and functional analyses in combination with mathematical simulations show that Net4 softens the mechanical properties of native BMs by opening laminin node complexes, decreasing cancer cell potential to transmigrate this barrier despite creating bigger pores. Our results therefore reveal that BM stiffness is dominant over pore size, and that the mechanical properties of 'normal' BMs determine metastases formation and patient survival independent of cancer-mediated alterations. Thus, identifying individual Net4 protein levels within native BMs in major metastatic organs may have the potential to define patient survival even before tumour formation. The ratio of Net4 to laminin molecules determines BM stiffness, such that the more Net4, the softer the BM, thereby decreasing cancer cell invasion activity.

Annual and seasonal patterns in etiologies of pediatric community-acquired pneumonia due to respiratory viruses and Mycoplasma pneumoniae requiring hospitalization in South Korea.

BACKGROUND: Community-acquired pneumonia (CAP) is one of the leading worldwide causes of childhood morbidity and mortality. Its disease burden varies by age and etiology and is time dependent. We aimed to investigate the annual and seasonal patterns in etiologies of pediatric CAP requiring hospitalization. METHODS: We conducted a retrospective study in 30,994 children (aged 0-18 years) with CAP between 2010 and 2015 at 23 nationwide hospitals in South Korea. Mycoplasma pneumoniae (MP) pneumonia was clinically classified as macrolide-sensitive MP, macrolide-less effective MP (MLEP), and macrolide-refractory MP (MRMP) based on fever duration after initiation of macrolide treatment, regardless of the results of in vitro macrolide sensitivity tests. RESULTS: MP and respiratory syncytial virus (RSV) were the two most commonly identified pathogens of CAP. With the two epidemics of MP pneumonia (2011 and 2015), the rates of clinical MLEP and MRMP pneumonia showed increasing trends of 36.4% of the total MP pneumonia. In children < 2 years of age, RSV (34.0%) was the most common cause of CAP, followed by MP (9.4%); however, MP was the most common cause of CAP in children aged 2-18 years of age (45.3%). Systemic corticosteroid was most commonly administered for MP pneumonia. The rate of hospitalization in intensive care units was the highest for RSV pneumonia, and ventilator care was most commonly needed in cases of adenovirus pneumonia. CONCLUSIONS: The present study provides fundamental data to establish public health policies to decrease the disease burden due to CAP and improve pediatric health.

Lifetime prevalence of childhood eczema and the effect of indoor environmental factors: Analysis in Hispanic and non-Hispanic white children.

BACKGROUND: The prevalence of eczema varies markedly across the globe. It is unclear whether the geographic variation is due to race and/or ethnic differences, environmental exposures, or genetic factors. OBJECTIVE: We investigated the effects of ethnicity and environmental exposures on eczema in Hispanic white and non-Hispanic white children who participated in the Southern California Children's Health Study. METHODS: We performed a cross-sectional study with sociodemographic predictors and environmental exposures among Hispanic white and non-Hispanic white children ages 4-8 years enrolled in the Children's Health Study, 2002-2003. RESULTS: Eczema prevalence differed by ethnicity: Hispanic whites showed lower prevalence (13.8%) compared with non-Hispanic whites (20.2%), and adjustment for sociodemographic factors did not account for the ethnic difference (odds ratio [OR] 0.79 [95% confidence interval {CI}, 0.65-0.95]). Parental history of allergic disease had a larger effect in Hispanic whites than in non-Hispanic whites (p for interaction = 0.005). High maternal education level (OR 1.46 [95% CI, 1.14-1.87]), parental history of allergic disease (OR 2.21 [95% CI, 1.78-2.76]), and maternal smoking during pregnancy (OR 1.44 [95% CI, 1.06-1.95]) increased the risk of eczema. Indoor environmental factors (e.g., mold, water damage, humidifier use) increased the risk of eczema in non-Hispanic whites independent of a parental history of allergic disease, but, in Hispanic whites, increased risks were observed, primarily in children without a parental history of allergic disease. CONCLUSION: Hispanic white children in southern California had a lower prevalence of eczema than non-Hispanic whites, and this ethnic difference was not accounted for by sociodemographic differences. The effects of a parental history of allergic disease and indoor environmental exposures on eczema varied by ethnicity, which indicated that the etiology of eczema may differ in Hispanic whites and in non-Hispanic whites.

Modification of additive effect between vitamins and ETS on childhood asthma risk according to GSTP1 polymorphism: a cross -sectional study.

BACKGROUND: Asthma is characterized by airway inflammation, and bronchial airways are particularly susceptible to oxidant-induced tissue damage. OBJECTIVE: To investigate the effect of dietary antioxidant intake and environmental tobacco smoke (ETS) on the risk of childhood asthma according to genotypes susceptible to airway diseases. METHODS: This cross-sectional study included 1124 elementary school children aged 7-12 years old. Asthma symptoms and smoking history were measured using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Intake of vitamin A (including retinol and ß-carotene), C, and E was measured by a semi-quantitative food frequency questionnaire (FFQ). GSTP1 polymorphisms were genotyped from peripheral blood samples. RESULTS: ETS was significantly associated with presence of asthma symptoms (adjusted odds ratio [aOR], 2.48; 95 % confidence interval [CI], 1.29-4.76) and diagnosis (aOR, 1.91; 95 % CI, 1.19-3.06). Dietary antioxidant intake was not associated with asthma symptoms, although ETS plus low vitamin A intake showed a significant positive association with asthma diagnosis (aOR, 2.23; 95 % CI, 1.10-4.54). Children with AA at nucleotide 1695 in GSTP1 who had been exposed to ETS and a low vitamin A intake have an increased risk of asthma diagnosis (aOR, 4.44; 95 % CI,1.58-12.52) compared with children who had not been exposed to the two risk factors. However, ETS exposure and low vitamin A intake did not significantly increase odds of asthma diagnosis in children with AG or GG genotypes. CONCLUSION: Low vitamin A intake and ETS exposure may increase oxidative stress and thereby risk for childhood asthma. These relationships may be modified by gene susceptibility alleles of GSTP1.

Pulmonary lymphomatoid granulomatosis in a 4-year-old girl.

Lymphomatoid granulomatosis is a rare lymphoproliferative disease associated with the Epstein-Barr virus that commonly affects the lung. There is limited literature on cases of pediatric lymphomatoid granulomatosis. Half of all cases of lymphomatoid granulomatosis develop during the treatment of leukemia. Herein, we describe a case of lymphomatoid granulomatosis in a previously healthy child without leukemia.

Association between cord blood 25-hydroxyvitamin D concentrations and respiratory tract infections in the first 6 months of age in a Korean population: a birth cohort study (COCOA).

PURPOSE: Previous studies suggest that the concentration of 25-hydroxyvitamin D [25(OH)D] in cord blood may show an inverse association with respiratory tract infections (RTI) during childhood. The aim of the present study was to examine the influence of 25(OH)D concentrations in cord blood on infant RTI in a Korean birth cohort. METHODS: The levels of 25(OH)D in cord blood obtained from 525 Korean newborns in the prospective COhort for Childhood Origin of Asthma and allergic diseases were examined. The primary outcome variable of interest was the prevalence of RTI at 6-month follow-up, as diagnosed by pediatricians and pediatric allergy and pulmonology specialists. RTI included acute nasopharyngitis, rhinosinusitis, otitis media, croup, tracheobronchitis, bronchiolitis, and pneumonia. RESULTS: The median concentration of 25(OH)D in cord blood was 32.0 nmol/L (interquartile range, 21.4 to 53.2). One hundred and eighty neonates (34.3%) showed 25(OH)D concentrations less than 25.0 nmol/L, 292 (55.6%) showed 25(OH)D concentrations of 25.0-74.9 nmol/L, and 53 (10.1%) showed concentrations of ≥75.0 nmol/L. Adjusting for the season of birth, multivitamin intake during pregnancy, and exposure to passive smoking during pregnancy, 25(OH)D concentrations showed an inverse association with the risk of acquiring acute nasopharyngitis by 6 months of age (P for trend=0.0004). CONCLUSION: The results show that 89.9% of healthy newborns in Korea are born with vitamin D insufficiency or deficiency (55.6% and 34.3%, respectively). Cord blood vitamin D insufficiency or deficiency in healthy neonates is associated with an increased risk of acute nasopharyngitis by 6 months of age. More time spent outdoors and more intensified vitamin D supplementation for pregnant women may be needed to prevent the onset of acute nasopharyngitis in infants.

Association of antioxidants with allergic rhinitis in children from seoul.

PURPOSE: The prevalence of allergic diseases has risen over the last few decades. Many factors, including environmental factors such as those related to diet, have been considered. Among dietary factors, intake of antioxidant-related nutrients has been associated with the risk of allergic disease. We investigated the association of antioxidant nutritional status with allergic rhinitis (AR) in Korean schoolchildren aged 6-12 years. METHODS: Subjects were 4,554 children in Seoul, Korea. The risk of allergic disease was measured using the Korean version of the International Study of Asthma and Allergies in Childhood, and dietary intake was measured by a semi-quantitative food frequency questionnaire. Intake of vitamins A (including retinol and ß-carotene), C, and E was used in the analysis. RESULTS: Vitamin C intake was negatively associated with an increased risk of current symptoms (adjusted odds ratio, 0.886; 95% confidence interval, 0.806-0.973). There was no association between AR and intake of vitamin A, retinol, ß-carotene, or vitamin E. Total serum IgE level and sensitization to allergen did not differ according to nutrient intake. CONCLUSIONS: The group of children with increased vitamin C consumption had fewer AR symptoms, despite the lack of a difference in total serum IgE level or allergen sensitization. These findings suggest that nutrient intake, especially that of vitamin C, influences AR symptoms.

Successful treatment of steroid-dependent eosinophilic cellulitis with cyclosporine.

Eosinophilic cellulitis (EC) is a rare idiopathic disorder, first described as a "recurrent granulomatous dermatitis with eosinophilia", that mimics cellulitis of infectious origin. We describe here a previously healthy 11-year-old girl who experienced fever and tender erythematous patch lesions after trauma to her knees. Because of the relapsing cellulitis-like skin lesions, skin biopsies were taken, resulting in a diagnosis of EC. The patient responded well to oral prednisolone but experienced side effects and relapse during dose tapering. She was switched from prednisolone to cyclosporine. Her EC remained under control, and she showed no evidence of relapse after discontinuation of cyclosporine.

The role of TNF-alpha in eosinophilic inflammation associated with RSV bronchiolitis.

The purpose of our study was to investigate whether tumor necrosis factor (TNF)-alpha correlates with eosinophilic inflammation that occurs during a lower respiratory tract infection with the respiratory syncytial virus (RSV) in children. Sixty children with RSV bronchiolitis (RSV group) and 20 healthy children with no respiratory symptoms (Control group) were enrolled. We measured the nasal lavage fluid (NLF) Th2 cytokine (IL-5), proinflammatory cytokine (TNF-alpha, IL-8), eosinophil-active cytokine [granulocyte-macrophage colony stimulating factor (GM-CSF), IFN-gamma], and eosinophil-active chemokine (eotaxin, regulated on activation normal T cell excreted and secreted) levels for both groups. We also measured serum eosinophil-degranulation product (eosinophil-derived neurotoxin; EDN, eosinophil cationic protein; ECP) levels from RSV group. TNF-alpha, IL-8, GM-CSF, IFN-gamma, and eotaxin levels were significantly higher in the RSV group compared with the Control group. TNF-alpha correlated with GM-CSF (r = 0.87, p < 0.0001), IFN-gamma (r = 0.92, p < 0.0001), eotaxin (r = 0.64, p < 0.0001), and IL-8 (r = 0.84, p < 0.0001). TNF-alpha may have an important role in eosinophilic inflammation of airways in children with RSV bronchiolitis.

Protein microarray analysis in patients with asthma: elevation of the chemokine PARC/CCL18 in sputum.

BACKGROUND: Microarray technology offers a new opportunity to gain insight into global gene and protein expression profiles in asthma. To identify novel factors produced in the asthmatic airway, we analyzed sputum samples by using a membrane-based human cytokine microarray technology in patients with bronchial asthma (BA). METHODS: Induced sputum was obtained from 28 BA subjects, 20 nonasthmatic atopic control (AC) subjects, and 38 nonasthmatic nonatopic normal control (NC) subjects. The microarray samples of subjects were randomly selected from nine BA subjects, three AC subjects, and six NC subjects. Sputum supernatants were analyzed using a custom human cytokine array (RayBio Custom Human Cytokine Array; RayBiotech; Norcross, GA) designed to analyze 79 specific cytokines simultaneously. The levels of growth-regulated oncogene (GRO)-alpha, eotaxin-2, and pulmonary and activation-regulated chemokine (PARC)/CCL18 were measured by sandwich enzyme-linked immunosorbent assays (ELISAs), and eosinophil-derived neurotoxin (EDN) was measured by radioimmunoassay. RESULTS: By microarray, the signal intensities for GRO-alpha, eotaxin-2, and PARC were significantly higher in BA subjects than in AC and NC subjects (p = 0.036, p = 0.042, and p = 0.033, respectively). By ELISA, the sputum PARC protein levels were significantly higher in BA subjects than in AC and NC subjects (p < 0.0001). Furthermore, PARC levels correlated significantly with sputum eosinophil percentages (r = 0.570, p < 0.0001) and the levels of EDN (r = 0.633, p < 0.0001), the regulated upon activation, normal T cell expressed and secreted cytokine (r = 0.440, p < 0.001), interleukin-4 (r = 0.415, p < 0.01), and interferon-gamma (r = 0.491, p < 0.001). CONCLUSIONS: By a nonbiased screening approach, a chemokine, PARC, is elevated in sputum specimens from patients with asthma. PARC may play important roles in development of airway eosinophilic inflammation in asthma.

TNF-alpha (-308 G/A) and CD14 (-159T/C) polymorphisms in the bronchial responsiveness of Korean children with asthma.

BACKGROUND: TNF-alpha is a pivotal proinflammatory cytokine increased in asthmatic airways. The TNF-alpha gene family might be linked to asthma or bronchial hyperresponsiveness (BHR), and TNF-alpha production might be modulated by CD14(+) cells. OBJECTIVE: We investigated the association between asthma susceptibility or asthma-related phenotypes and TNF-alpha (-308G/A) polymorphism and examined the combined effect with CD14 (-159T/C) polymorphism in Korean children. METHODS: Asthmatic (n = 788) and control (n = 153) children were evaluated for asthma phenotypes. Genotypes were determined by using the single-base extension method and PCR-restriction fragment length polymorphism. RESULTS: There was no difference between asthmatic children and control subjects in terms of the allele frequencies of TNF-alpha (-308G/A) and CD14 (-159T/C). Significantly lower PC(20) values were seen in asthmatic (P = .016) children with the TNF-alpha risk allele (-308A). Higher frequencies of 1 or 2 copies of the risk allele were found in asthmatic children with moderate-to-severe BHR to methacholine and exercise compared with control children (adjusted odds ratio of 2.57 [95% CI, 1.30-5.08] and adjusted odds ratio of 2.04 [95% CI 0.99-4.20], respectively). In addition, asthmatic children with risk alleles at both loci had significantly greater BHR than those homozygous for the common alleles (P = .018). CONCLUSION: The TNF-alpha promoter polymorphism (-308G/A) might be associated with severe BHR in Korean children with asthma. In addition, these children show a synergistic effect between the TNF-alpha promoter (-308A) and CD14 promoter (-159C) polymorphisms in terms of BHR. CLINICAL IMPLICATIONS: The TNF-alpha polymorphism might be a disease-modifying gene in asthma and modulated by the CD14 gene.

Placement of covered retrievable expandable metallic stents for pediatric tracheobronchial obstruction.

PURPOSE: To evaluate the safety and clinical effectiveness of placement of covered retrievable expandable metallic stents in seven children with tracheobronchial obstruction. MATERIALS AND METHODS: Using bronchoscopic and fluoroscopic guidance, stent placement was performed in seven children (median age, 12 y; range, 2 mo-14 y). The stents were electively removed 6 months after placement or whenever there were symptom-producing complications. During the follow-up period, technical and clinical success, complications and related reinterventions, and long-term prognosis were retrospectively evaluated. RESULTS: Stent placement was technically successful for a total of eight stents in all seven patients. Stent removal was also successful for six stents in five patients; two stents were removed electively 6 months after placement, and four stents were removed due to symptom-producing complications. Clinical success defined as ventilator weaning, extubation, or dyspnea improvement was achieved in all patients 1 week after stent placement. A possible infection source in one stent and abundant granulation tissue caused by three stents necessitated removal of four stents in three patients. During the mean follow-up period of 18.7 months (range, 1-31 mo) after stent placement, three patients died due to the progression of underlying cardiopulmonary disease or malignancy. There were no deaths directly related to stent placement or related complications. CONCLUSION: Although the findings were based on a small series, placement of covered retrievable expandable metallic stents seems to be safe and effective for the treatment of pediatric tracheobronchial obstruction. Ventilator weaning, extubation, or dyspnea improvement was possible in all patients after stent placement.

Familial interstitial lung disease in two young Korean sisters.

Most of the interstitial lung diseases are rare, chronic, progressive and fatal disorders, especially in familial form. The etiology of the majority of interstitial lung disease is still unknown. Host susceptibility, genetic and environmental factors may influence clinical expression of each disease. With familial interstitial lung diseases, mutations of surfactant protein B and surfactant protein C or other additional genetic mechanisms (e.g. mutation of the gene for ATP-binding cassette transporter A3) could be associated. We found a 21 month-old girl with respiratory symptoms, abnormal radiographic findings and abnormal open lung biopsy findings compatible with nonspecific interstitial pneumonitis that is similar to those of her older sister died from this disease. We performed genetic studies of the patient and her parents, but we could not find any mutation in our case. High-dose intravenous methylprednisolone and oral hydroxychloroquine were administered and she is still alive without progression during 21 months of follow-up.

Prolonged effect of montelukast in asthmatic children with exercise-induced bronchoconstriction.

Accumulating evidence shows that cysteinyl leukotrienes are the most important mediators in exercise-induced bronchoconstriction (EIB). In contrast to several studies in adults, there are few long-term studies of leukotriene receptor antagonists (LTRAs) in children with EIB. The aim of this study was to assess the prolonged clinical and bronchoprotective effects of montelukast in asthmatic children with EIB. We randomly assigned 64 asthmatic children with EIB. Forty subjects received montelukast (5 mg/day), and 24 subjects received placebo once daily for 8 weeks. Exercise challenge was performed before and after 8 weeks of treatment. Of the 40 patients in the montelukast group, 28 patients crossed over after 8 weeks. The response was measured as asthma symptom score, maximum percent fall in forced expiratory volume in 1 sec (FEV(1)) from pre-exercise baseline, and time to recovery of FEV(1) to within 10% of pre-exercise baseline (time to recovery). Following 8 weeks of treatment with montelukast, the montelukast group compared with placebo showed significant improvements in all endpoints, including asthma symptom score, maximum percent fall in FEV(1) after exercise, and time to recovery. In the cross-over group, even 8 weeks after stopping montelukast treatment, all endpoints were significantly and persistently improved. These results indicate that montelukast provides clinical protection from airway hyperresponsiveness in asthmatic children with EIB, and suggest that LTRAs may be useful for the long-term management of asthmatic children with EIB.