The hygiene hypothesis, first proposed in 1989, suggested that reduced exposure to infections in early life leads to allergic diseases by the defects in the establishment of immune tolerance. Although many studies provided evidence that some exposure conditions, including family size, antibiotics, probiotics, and viral or bacterial infections, are strongly related to the prevalence of allergic diseases, thereby supporting the hygiene hypothesis, some evidence does not provide acceptable results for the hygiene hypothesis. Further, most studies have focused on patients with asthma or atopic dermatitis, not allergic rhinitis. In this review, we summarize the recent studies for and against the ‘hygiene hypothesis’ and identify causal association with the prevalence of allergic rhinitis.

Primary pneumatization of the frontal bone occurs in the first year of life, but further pneumatization continues until 18 years of age. Elongation of the ethmoidal infundibulum and frontal recess, or upwards migration of the anterior ethmoidal cells has been proposed as a mechanism of frontal sinus development. The frontal sinus drainage pathway is displaced in the anterior or posterior direction depending on the pneumatization pattern of the frontoethmoidal cells. Also, frontal sinuses can be connected to the infundibulum or directly to the middle meatus depending on the superior attachment pattern of the uncinate process. Bilateral frontal sinuses are separated by their bony septum, and thus have their own drainage pathways. Contrary to this general rule, we experienced two cases of frontal sinuses that were connected to each other, showing a single drainage pathway from both frontal sinuses. We report these two cases along with a literature review.

Allergic rhinitis (AR) is a type of rhinitis accompanied by sensitization to allergens. One of the most clinically important allergens is pollen. Recently, due to climate change and CO 2 air pollution, the flowering period starts earlier and persists longer. In addition, antigenicity due to environmental pollution is also being strengthened. As a result, the sensitization rate to pollen antigens is on the rise. It is known that the prevalence of AR especially caused by pollen is rapidly escalating. Although the causal relationship between pollen exposure and the severity of rhinitis is not precisely established, an association of rhinitis symptoms with the time of pollen scattering exists. In addition, the mixed effect of environmental pollution and pollen may play a role in the development of rhinitis symptoms. Therefore, in order to avoid pollen, it is necessary to constantly improve pollen forecast and minimize the contact with pollen indoors and outdoors. Treatment of AR should be performed according to guidelines. Also, continuous efforts to solve the environmental problems affecting the ecology of pollen are needed.

Semantic variant primary progressive aphasia (svPPA), a well-known subtype of the frontotemporal dementia often shows peculiar clinical features and structural neuroimage findings. To strengthen the accuracy of a clinical diagnosis, amyloid positron emission tomography-computed tomography (PET-CT) might be helpful. However, in patients with late-onset svPPA, an admixture of the various neuropathology would interfere with diagnostic approach. Herein, we report a case of late-onset bilateral svPPA showing a regional amyloid deposition on PET-CT scan.

The prevalence of allergic rhinitis in children and adolescents is constantly increasing. However, few studies exist on the relationship between smoking and allergic rhinitis. In addition to conventional cigarettes, electronic and heated cigarettes have recently been introduced, which have several harmful effects. It is hypothesized that smoking and rhinitis are correlated; however, this relationship is complex. Previous studies reported that exposure to smoking during pregnancy is associated with allergic rhinitis development.Unlike the varied results reported in adults, studies on children and adolescents have often correlated direct/indirect smoke with allergic rhinitis, with prolonged exposure being associated with a higher risk of allergic rhinitis, particularly when exposed at an early age. Nonallergic inflammatory reactions and immunoglobulin E-mediated allergic sensitization are assumed to be the underlying mechanisms for the association between allergic rhinitis and smoking. Measures to reduce smoking are warranted to lower the incidence of allergic rhinitis in children and adolescents and to improve their health.

Background/Aims: The safety of direct oral anticoagulants (DOACs) compared with warfarin in patients with both nonvalvular atrial fibrillation (AF) and clinically confirmed liver cirrhosis (LC) has not been well studied. We compared the risk of a major bleeding event between DOAC and warfarin treatments in this patient population. Methods: A total of 238 cirrhotic patients with AF were retrospectively analyzed. The major bleeding event risk was compared between DOAC- and warfarin-treated groups. The median follow-up duration was 5.6 years. Results: Among the 238 study patients with LC and AF, 128 (53.8%) received DOACs and 110 (46.2%) received warfarin. The mean patient age was 68.8 years, and 78.2% were men. A major bleeding event occurred in 10 and 20 patients in the DOAC and warfarin groups, respectively, most commonly caused by gastrointestinal bleeding (70.0%). The cumulative risk of major bleeding did not differ between the groups by log-rank test (p = 0.12). This finding did not change when using 60 propensity score-matched pairs. A multivariable Cox regression model indicated that the concomitant use of antiplatelet agents (adjusted hazard ratio [aHR], 2.06; 95% confidence interval [CI], 1.00 to 4.30; p = 0.048) and presence of esophageal or gastric varices confirmed by endoscopic examination (aHR, 2.31; 95% CI, 1.03 to 5.17; p = 0.04) were associated with major bleeding in the entire cohort. Conclusions A major bleeding event risk is not increased by DOAC compared with warfarin treatment. Antiplatelet agent use and varices are independently associated with a higher risk of major bleeding during anticoagulation.

Background: Atopic dermatitis (AD) is a heterogeneous disease with different age of onset, disease course, clinical symptoms, severity, and risk of comorbidity. The characteristics of children with AD also vary by age or country. However, little is known about the clinical characteristics of AD in Korean school-aged children and adolescents. Furthermore, there are few studies on phenotypic differences according to onset age. This study aimed to explore the clinical characteristics and phenotypes according to onset age and severity of AD in children and adolescents in Korea. Methods: AD patients aged 6–18 years who presented to 18 hospitals nationwide were surveyed.The patients were examined for disease severity by pediatric allergy specialists, and data on history of other allergic diseases, familial allergy history, onset age, trigger factors, lesion sites,treatment history and quality of life were collected. The results of the patient’s allergy test were also analyzed. The patients were classified into infancy-onset (< 2 years of age), preschoolonset (2–5 years of age), and childhood-onset (≥ 6 years of age) groups. Study population was analyzed for clinical features according to onset-age groups and severity groups. Results: A total of 258 patients with a mean age of 10.62 ± 3.18 years were included in the study. Infancy-onset group accounted for about 60% of all patients and presented significantly more other allergic diseases, such as allergic rhinitis and asthma (P = 0.002 and P = 0.001, respectively). Food allergy symptoms and diagnoses were highly relevant to both earlier onset and more severe group. Inhalant allergen sensitization was significantly associated with both infancy-onset group and severe group (P = 0.012 and P = 0.024, respectively). A family history of food allergies was significantly associated with infancyonset group (P = 0.036). Severe group was significantly associated with a family history of AD, especially a paternal history of AD (P = 0.048 and P = 0.004, respectively). Facial (periorbital, ear, and cheek) lesions, periauricular fissures, hand/foot eczema, and xerosis were associated with infancy-onset group. The earlier the onset of AD, the poorer the quality of life (P = 0.038). Systemic immunosuppressants were used in only 9.6% of the patients in the severe group. Conclusion This study analyzed the clinical features of AD in Korean children and adolescents through a multicenter nationwide study and demonstrated the phenotypic differences according to onset age and severity. Considering the findings that the early-onset group is more severe and accompanied by more systemic allergic diseases, early management should be emphasized in young children and infants.

The global worsening of air pollution has decreased the quality of life. Air pollutants can induce oxidative stress, epigenetic changes, and alterations to microRNA expression in the airway and skin, leading to immune dysregulation. Previous epidemiological studies suggest a strong association between outdoor environmental pollution and childhood allergic disease, especially allergic rhinitis (AR). Moreover, traffic-related air pollution has increased the severity and incidence of AR, and heavy traffic has been associated with an increased prevalence of AR. Thus, this review aimed to define outdoor environmental pollution and clarify the mechanisms by which air pollutants aggravate AR. In addition, we performed a systematic review and meta-analysis to summarize the findings of several domestic and international epidemiological and clinical studies about the effects of air pollution on AR in children.

The incidence of coronavirus diseases 2019 (COVID-19), including severe cases, has been increasing in both children and adolescents with the spread of the delta variant. COVID-19 vaccines have been identified to be effective in the prevention of COVID-19transmission in children and adolescents and keeping schools open. However, adverse reactions associated with COVID-19 vaccination in children and adolescents contribute to parents’ hesitation to proceed with vaccination, especially due to serious, albeit rare, reactions. The results from COVID-19 vaccine clinical trials on the safety and efficacy of COVID-19 vaccines in children and adolescents are promising in terms of their effects on COVID-19 infection prevention. In the present study, we summarize the adverse reactions of COVID-19 vaccines in children and adolescents, based on the clinical trials, mainly including Pfizer-BioNTech and Moderna COVID-19 vaccines. In the Pfizer-BioNTech COVID-19 clinical trials, the most common local adverse reaction was pain at the injection site in 74.1%–86%, depending on age, and the most common systemic adverse reaction was fatigue, followed by headache, myalgia, diarrhea, and fever with differences in the distribution according to age. There was no severe adverse reaction related to any COVID-19 vaccine in children and adolescents during the study period. In the mass vaccination program of COVID-19 in children and adolescent, myocarditis has rarely been diagnosed after COVID-19 vaccination, which most commonly occurred in boys after the second dose. Currently, Pfizer-BioNTech COVID-19 vaccines can be safely recommended in children and adolescents for the prevention of COVID-19 infection and the reduction in COVID-19 severity.