Patients with high T2 biomarkers are at risk of severe exacerbations (e.g. baseline fractional exhaled nitric oxide (FeNO) > 45 ppb predicts frequent exacerbation [17]), and in this group the key clinical question is whether this is because of non-adherence to inhaled corticosteroid treatment or whether they have relative corticosteroid-resistant T2-high asthma and require additional treatment with biological drugs that target T2 mechanisms (e.g. antibodies that inhibit interleukin (IL)-5 or IL-13 signalling). The gene discussed is IL13; the disease is asthma.