“… 11 Typical manifestations of DPB include chronic cough, expectoration and exertional dyspnoea, history of chronic sinusitis, high titre of serum cold agglutination test, centrilobular nodule shadow with tree‐in‐bud sign widely distributed in both lungs on chest CT scan and so on. 11 , 12 Akira et al 13 classified the patients into four stages according to the radiographic findings of DPB: Stage 1, diffuse centrilobular nodules; Stage 2, tree‐in‐bud sign; Stage 3, bronchiectasis in peripheral areas; and Stage 4, bronchiectasis in the central area. The pathological features of DPB are full‐thickness respiratory bronchiolitis with infiltration of lymphocytes, plasma cells and so on.…”