Patients with DPB show focal denudation of bronchiolar epithelial layers and, in some cases, peribronchiolar fibrotic changes or perifibrotic emphysematous changes. Centrilobular chronic inflammatory lesions can be seen, while the distal parts of lobules are free from marked changes. The centrilobular lesions show interstitial accumulations of foamy cells and lymphoid cells in the wall of respiratory bronchioles, adjacent alveolar ducts, and alveoli. Based on Kitaichi 12 Presentation Onset usually occurs after age 40 or 50 years, and the incidence tends to be higher in men than in women. Insidious and chronic expectoration of purulent sputum is found in the early stages of the disease, and progressive exertional dyspnea appears later.
Patients often have a past history of chronic paranasal sinusitis.
Crackles and rhonchi are heard in the inspiratory and expiratory phases on chest auscultation. In typical cases, diffusely disseminated fine nodular shadows with hyperinflation of the lungs are seen. As the disease advances, bronchiectasis is seen with the enlargement of nodular shadows. Compared to the chest radiograph, the chest CT shows bilateral small, centrilobular, nodular opacities and dilation of peripheral airways more clearly. The reason for this increase is unknown, but there is no evidence that it is related to the presence of mycoplasma infection.