In DPB, the nodules are more restricted to the respiratory bronchioles, while in OB they are often found in the membranous bronchioles (the initial non-cartilaginous section of the bronchiole, that divides from the tertiary bronchus) up to the secondary bronchus. OB is a bronchiolar disease with worldwide prevalence, while DPB has more localized prevalence, predominantly in Japan. Prior to clinical recognition of DPB in recent years, it was often misdiagnosed as bronchiectasia, COPD, IPF, phthisis miliaris, sarcoidosis or alveolar cell carcinoma. Treatment
Macrolide antibiotics, such as erythromycin, are an effective treatment for DPB when taken regularly over an extended period of time. Clarithromycin or roxithromycin are also commonly used. The successful results of macrolides in DPB and similar lung diseases stems from managing certain symptoms through immunomodulation (adjusting the immune response), which can be achieved by taking the antibiotics in low doses. Treatment consists of daily oral administration of erythromycin for two to three years, an extended period that has been shown to dramatically improve the effects of DPB. This is apparent when an individual undergoing treatment for DPB, among a number of disease-related remission criteria, has a normal neutrophil count detected in BAL fluid, and blood gas (an arterial blood test that measures the amount of oxygen and carbon dioxide in the blood) readings show that free oxygen in the blood is within the normal range. Allowing a temporary break from erythromycin therapy in these instances has been suggested, to reduce the formation of macrolide-resistant P. aeruginosa.
Diffuse panbronchiolitis (DPB) is an inflammatory lung disease of unknown cause. It is a severe, progressive form of bronchiolitis, an inflammatory condition of the bronchioles (small air passages in the lungs). The term diffuse signifies that lesions appear throughout both lungs, while panbronchiolitis refers to inflammation found in all layers of the respiratory bronchioles (those involved in gas exchange). DPB causes severe inflammation and nodule-like lesions of terminal bronchioles, chronic sinusitis, and intense coughing with large amounts of sputum production. The disease is believed to occur when there is susceptibility, or a lack of immune system resistance, to DPB-causing bacteria or viruses, caused by several genes that are found predominantly in individuals of East Asian descent. The highest incidence occurs among Japanese people, followed by Koreans. DPB occurs more often in males and usually begins around age 40. It was recognized as a distinct new disease in the early 1960s and was formally named diffuse panbronchiolitis in 1969. If left untreated, DPB progresses to bronchiectasis, an irreversible lung condition that involves enlargement of the bronchioles, and pooling of mucus in the bronchiolar passages. Daily treatment of DPB with macrolide antibiotics such as erythromycin eases symptoms and increases survival time, but the disease currently has no known cure. The eventual result of DPB can be respiratory failure and heart problems. Classification
The term "bronchiolitis" generally refers to inflammation of the bronchioles. DPB is classified as a form of "primary bronchiolitis", which means that the underlying cause of bronchiolitis is originating from or is confined to the bronchioles.