Is blood eosinophilia a treatable trait in chronic obstructive airway diseases?

Nowadays, the management of chronic obstructive airway diseases is shifting from traditional diagnostic labels toward a precision medicine approach based on "treatable traits." Among these, blood eosinophilia is emerging as a biomarker of type 2 (T2) inflammation across asthma and chronic obstructive airway diseases (COPD), even if its role as diagnostic tool and therapeutic target remains debated. In this manuscript we presented a clinical case of a 60-year-old male, former mild smoker (5 p/y), initially diagnosed with severe COPD with persistent airflow limitation, frequent severe exacerbations and persistent eosinophilia, but a history of asthma and nasal polyposis. After six months with optimization of inhaled therapy and clinical reassessment, the diagnosis of "severe COPD" shifted to the diagnosis of "severe eosinophilic asthma". Considering the new diagnosis, he was prescribed mepolizumab on top of triple inhaled therapy. After 1 year, the clinical response was excellent in terms of symptoms control, exacerbations reduction and OCS sparing, despite no improvement in lung function. Starting from this clinical case, the aim of this mini review is to describe the role of eosinophilic inflammation in asthma and COPD. While eosinophilic inflammation is a common feature of asthma, COPD is usually characterized by neutrophilic inflammation, even if, a subset of patients with COPD has eosinophilic inflammation. In this context, blood eosinophilia might represent a clinically actionable trait to guide diagnosis and personalized therapy in chronic airway diseases even if it should not be targeted in isolation but be integrated into a multidimensional assessment.