Food allergy has emerged as an important public health problem affecting people of all ages in many countries. The prevalence varies according to age, geographic regions, and ethnicity. For several years, many studies have suggested that the prevalence of food allergy is increasing at an alarming rate, for unclear reasons. Conversely, some studies have also provided findings that sensitization to common food allergens did not increase. Increased recognition rather than an actual increase in patients with IgE-mediated food allergy might lead to the increases in the prevalence of self-reported or physician-diagnosed food allergy. It is also noted that the prevalence of food allergy differs even in the same region according to the study design, i.e., hospital-based or community-based studies. Despite these limitations, epidemiologic data are important because they provide useful information on diagnosis, treatment, and prevention of food allergy. This review focuses on advances in the epidemiology of food allergy in Korean children.

Bronchial provocation tests are of value in the evaluation of airway hyperresponsiveness. Nonspecific bronchial challenge (methacholine, mannitol, exercise, etc.) is used when the symptoms, physical examination, and measurements of pulmonary function are unremarkable in the diagnosis of asthma, when a patient is suspected of having occupational asthma or exercise-induced bronchoconstriction (EIB), and when a screening test for asthma or EIB is required for some occupational groups in whom bronchospasm would pose an unacceptable hazard. Methacholine inhalation challenge is most widely used pharmacologic challenge and highly sensitive. For appropriate interpretation of the results of methacholine provocation, it is important to perform the test with the standardized protocol and to recognize that inhalation methods significantly influence the sensitivity of the procedure. Indirect challenges (e.g., mannitol and exercise) correlate with airway inflammation and are more specific but less sensitive for asthma. Indirect provocation tests are used to confirm asthma, to differentiate asthma from other airway diseases, and to evaluate EIB.

Purpose: Drug provocation tests (DPT) are the gold standard for confirming the diagnosis of drug hypersensitivity reactions (DHRs). However, there are little studies of DPT in children. The purpose of this study was to evaluate DPT results and safety as diagnostic methods of DHR in Korean children. Methods: We reviewed the medical records of 39 children under 18 years of age with a suspected DHR and performed DPT between January 2010 and May 2016 at Asan Medical Center. Results: Total 110 DPT were performed in 39 children (20 boys and 19 girls) with a history of DHR. Clinical presentation of DHR included skin rash (n = 7), pruritus (n = 3), urticaria (n = 18), angioedema (n = 19), dyspnea (n = 5), hoarseness (n = 1), hypothermia (n= 1), and anaphylaxis (n= 5). The median age at the time of DPT was 9 years. Positive DPT were observed in 21 of 39 children (53.8%) and 28 of 110 cases (25.5%). Drugs causing positive reactions were acetaminophen in 50% (9 of 18), nonsteroidal anti-inflammatory drugs in 29.2% (14 of 48), cephalosporin in 9.1% (1 of 11), trimethoprim/sulfamethoxazole in 50% (1 of 2), local anesthetics in 10% (1 of 10), and others (levodropropizine and idursulfase) in 15.4% (2 of 13). There was no statistical difference between children who had positive and negative results in sex, age, personal and parental history of allergic disease, eosinophil count, or total IgE level. Children with positive DPT did not develop anaphylaxis during the DPT procedure. Conclusion: Drug provocation test is safe, and it can be considered in children with suspected DHRs.

Purpose: Recently, the prevalence and disease burden of asthma have increased. Thus, the need for early diagnosis and appropriate management of asthma is emerging. However, it is difficult to identify the diagnosis, symptoms and the prevalence of asthma due to lack of reliable investigating items. The purpose of this study was to develop a standardized survey format in order to assess the prevalence of asthma in Koreans. Methods: We investigated surveys and related information that are utilized to assess asthma diagnosis and prevalence by systematic review. After that, Delphi survey was conducted on 44 Korean allergists in order to develop a standardized survey in Korea. The process consisted of 3 serial rounds across 3 age groups. Each subsequent round narrowed investigating items for the decision of standard set about asthma prevalence, current asthma, and asthma aggravation. Results: Lifetime asthma was defined as "ever doctor-diagnosed asthma" in all age groups. Current asthma was defined as "treatment for asthma during the past 12 months" in all age groups, and "doctor-diagnosed asthma during the past 12 months" was added on the ${\geq}5$-year-old and adult groups. "Wheezing ever" was defined as "wheezing at any time in the past," and current wheeze was defined as "wheezing in the last 12 months." Asthma aggravation was defined as "visits at the emergency department or admission due to asthma attack within the last 12 months" in all age groups. Conclusion: We established applicable nationwide definitions of "lifetime asthma," "current asthma," and "asthma aggravation" in Koreans by the Delphi survey.

Purpose: Serum vitamin D (25-hydroxyvitamin D, 25[OH] D) and interleukin-31 (IL-31) are related to atopic dermatitis, but their relationship with allergic rhinitis is unclear. The purpose of this study was to compare the levels of serum IL-31 and 25 (OH) D between the allergic rhinitis (AR), nonallergic rhinitis (NAR), and control groups and to investigate the relationship between IL-31 and 25 (OH) D. Methods: We recruited 59 children with only rhinitis and 33 controls without any allergic diseases. Serum IL-31 and 25(OH) D levels were assayed using an enzyme-linked immunosorbent assay and high-performance liquid chromatography, respectively. The patients were considered to have atopic sensitization if the levels of serum specific IgE to inhalant allergens as assessed using immunoCAP were ${\geq}0.35IU/mL$ or if they tested positive for one or more allergens by the skin prick test. Results: Of children with rhinitis, 25 had nonatopy (NAR), and 34 children had atopy (AR). Serum 25(OH) D levels were significantly lower in the rhinitis group than in the control group, while there was no significant difference serum 25(OH) D levels between the AR and NAR groups. Children with rhinitis demonstrated higher serum IL-31 levels than controls; however, there was no difference in serum IL-31 levels between the AR and NAR groups. Serum 25(OH) D levels were inversely correlated with serum IL-31 levels and blood eosinophil counts. On the other hand, serum 25(OH) D levels were not correlated with total serum IgE levels. Conclusion: Serum 25(OH) D and IL-31 may play a role in the pathogenesis of rhinitis via mechanisms other than IgE-related pathway.

Purpose: The aim of this study was to evaluate the severity of disease in children with acute bronchiolitis according to the type of infected virus. Methods: From November 2007 to May 2015, 768 patients under 2 years of age who underwent real time-polymerase chain reaction of nasopharyngeal aspirates admitted to the Department of Pediatrics of Dongguk University Ilsan Hospital for acute bronchiolitis were enrolled. Severe bronchiolitis was defined as presence of one or more kinds among tachypnea, chest retraction, needs of $O_2$ inhalation or ventilator care. Results: The severity of bronchiolitis was increased with shorter fever duration (P< 0.001) and previous wheezing episodes (P= 0.005). In the case of single infection, respiratory syncytial virus (RSV) A only increased the severity of acute bronchiolitis (P= 0.012). However, the severity of illness decreased when RSV A coinfected with adenovirus (P= 0.034), human rhinovirus (P= 0.038), or human coronavirus NL63 (P= 0.042). On the other hand, when human rhinovirus was coinfected with enterovirus (P= 0.013) or parainfluenza 3 (P= 0.019), the severity was increased. When human metapneumovirus coinfected with human bocavirus, the severity was increased (P= 0.038). Conclusion: Acute bronchiolitis was associated with increased severity only when RSV A infected solely, but several viruses increased or decreased the severity when coinfection occurred. Therefore, it may be helpful in predicting the course of the acute bronchiolitis according to the affected virus.

Purpose: This report describes the results of a survey of the characteristics of pertussis in children from a single institution and compares it to data from the Korea Centers of Disease Control (KCDC). Methods: We retrospectively evaluated the medical records of 17 and 6 patients diagnosed with pertussis and parapertussis, respectively, at Soonchunhyang University Bucheon Hospital from January 2005 to January 2017. Results: Of the 17 patients with pertussis, 9 were under 1 year of age (52.9%), 3 were aged between 1 and 10 years (17.6%), and 5 were over 10 years of age (29.4%). Seven patients (41.2%) had never received diphtheria-tetanus-acellular pertussis vaccines, of which 5 were infants below 2 months of age and 2 were 10 years old and lived in China. Four patients showed the initial symptoms of cough in China. The sources of infection were the parents (2 cases) and the siblings (8 cases). All patients showed prolonged severe cough and the average duration of cough was 26 days. Severe symptoms, including dyspnea, cyanosis, apnea, and seizures, were observed in the children under 2 months of age. According to the recent 10-year KCDC data, the highest rate of pertussis diagnosis was noted in infants (47.8%), followed by adolescents (18.7%). Six patients with parapertussis also presented with prolonged severe cough without any other severe symptoms. Lymphocytosis was not found, unlike the patients with pertussis. Conclusion: The possibility of pertussis and parapertussis should be considered among patients with prolonged severe cough, especially in infants and adolescents.

Purpose: Refractory Mycoplasma pneumonia (RMP) has been increasing not only in Korea but worldwide. We investigated the incidence of M. pneumonia resistant to macrolides and risk factors for RMP. Methods: From October 2015 to May 2016, 62 pediatric patients who were admitted due to pneumonia diagnosed on the basis of chest x-ray with respiratory symptoms and positive for M. pneumoniae in polymerase chain reaction with no evidence of other bacterial or viral infections were included. Sequence analysis of the 23S rRNA gene in M. pneumoniae was performed to identify macrolide resistance. Patients with congenital anomalies, history of pulmonary disease, and unclear information on antibiotic use were excluded. Results: Mutations in the 23S rRNA gene were detected in 50 of 62 patients (80.6%). Risk factors were analyzed in only 45 patients. The RMP group consisted of 26 patients (57.8%) who had fever lasting more than 5 days and deteriorating chest x-ray findings. The lactate dehydrogenase (LDH) and C-reactive protein (CRP) levels were significantly higher in the RMP group than in the non-RMP group (LDH: $300{\pm}79U/L$ vs. $469{\pm}206U/L$, CRP: $4.9{\pm}4.3mg/dL$ vs. $2.5{\pm}1.7mg/dL$; P= 0.04 vs. P= 0.026). In univariate analysis, the RMP group was significantly associated with 23S rRNA gene mutation, lobar pneumonia, and pleural effusion (odds ration [OR]: 10.8, 4.1, 5.3; P= 0.004, P= 0.036, P= 0.046). The presence of macrolide resistance was found to be only a significant risk factor in logistic regression (OR; 8.827; 95% confidence interval, 1.376-56.622; P= 0.022). Conclusion: Macrolide resistance was a significant risk factor in patients with RMP and identification of macrolide resistance might be helpful in predicting RMP and establishing target therapy for RMP.

Fluconazole is a triazole-based first-generation antifungal agent and has excellent effects on candidiasis and cryptococcosis. Hypersensitivity has been reported as a side effect of fluconazole. A 76-year-old female patient used fluconazole for consolidation therapy for cryptococcal meningitis, but showed delayed hypersensitivity with skin rashes and itching sensation of the whole body. For desensitization, was attempted by administering 12-step, 1:1 fluconazole solutions were administered intravenously at sequentially increasing infusion rates. After successful quick desensitization to fluconazole, fluconazole was continuously used as a consolidation therapy for cryptococcal meningitis. We herein report a case of delayed hypersensitivity reaction to fluconazole in consolidation therpy with cryptococcal meningitis who successfully completed desensitization.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare systemic vasculitis that commonly affects the peripheral nervous system. EGPA rarely presents with acute polyneuropathy resembling $Guillain-Barr{\acute{e}}$ syndrome (GBS). A 51-year-old female patient with a history of asthma suddenly developed bilateral lower extremityparesthesia that progressed to asymmetric ascending paralysis within 10 days of onset. Nerve conduction study results were compatible with acute motor sensory axonal neuropathy, consistent with a GBS subtype. A clinical and neurophysiological diagnosis of GBS was made, and high-dose intravenous immunoglobulins were administered. However, the patient's painful motor weakness persisted. Furthermore, she had newly developed skin lesions on her back, face, and arms. Her blood test revealed marked eosinophilia (> 60%). In addition, antineutrophil cytoplasmic antibodies were reported positive. A Water's view radiographic image showed bilateral maxillary sinusitis. Considering the history of asthma, we suspected EGPA-associated polyneuropathy and started steroid treatment. The patient's strength and eosinophilia improved rapidly and dramatically. EGPA can mimic GBS and should be differentiated because of different treatment strategies. Early diagnosis and prompt treatment help achieve a good outcome.