Allergology international : official journal of the Japanese Society of Allergology
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The characteristic phenotype of severe asthma in Japan seems to be distilled into the following two features: low incidence of obesity and high prevalence of patients with type 2 inflammation. Only 5-7% of Japanese severe asthma patients had a body mass index (BMI) ≥30 kg/m2, and more than 80% of patients with severe asthma exhibited type 2 inflammation. Although the relationship between obesity and non-type 2 inflammation is complex, the low incidence of obesity might explain the prevalence of type 2 inflammation. ⋯ Although the prevalence of severe asthma is comparable to Western countries, the rate of asthma death and disease burden seems to be lower in Japan. These trends might be due to the system of public health insurance for the whole nation, leading to good access to hospital and asthma specialists due to the geographically narrow country. In this review article, we will discuss the definition, epidemiology, comorbidities, biomarkers, specific phenotype, and current treatment for severe asthma in Japan.
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Asthma is a heterogeneous disease with considerable variability noted in disease severity, patterns of airway inflammation, and achievement of disease control on current medications. An absence of disease control is most frequently noted in patients with severe asthma, and is defined as a lack of control while on high dose inhaled corticosteroids (ICS) plus a second controller medication. In part, this lack of control may relate to a diminished effect of current guideline-directed care on the existing pattern of airway inflammation in severe asthma. ⋯ The available monoclonal antibodies include omalizumab (anti-IgE); mepolizumab, reslizumab and benralizumab (anti-IL-5 pathways), and dupilumab (anti-IL-4/IL-13). The use of these T2-high interventions has led to significant reductions in asthma symptoms, a decreased frequency of exacerbations, and improved lung function in many patients. Not only has the use of these monoclonal antibodies led to improved asthma control in patients with severe disease, their use has provided insight into mechanisms of severe asthma.