Diffuse panbronchiolitis is a progressive obstructive small-airway disease associated with sinusitis that occurs primarily in adults of Japanese heritage. The disease is typically complicated by infections and, when untreated, leads to bronchiectasis and eventually death. An association with rheumatoid arthritis in Japan has been reported.

Grossly, bronchiolocentric yellow 1- to 3-mm nodules are present. Histologically, the bronchiolar interstitium in diffuse panbronchiolitis is infiltrated by foamy macrophages, lymphocytes, and plasma cells. Follicular bronchiolitis may be present, and there may be histopathologic findings of superimposed acute or organizing pneumonia.