DISCUSSION: The majority of patients diagnosed with DIPNECH are middle-aged nonsmoking females, with nonspecific respiratory symptoms, commonly misdiagnosed as asthma or chronic obstructive pulmonary disease. The gold standard for diagnosis remains surgical lung biopsy with demonstration of neuroendocrine cell proliferation confined to the epithelium of large and small airways. Tumorlets can be localized or diffuse and commonly produce bombesin and gastrin-releasing peptides that stimulate fibroblasts leading to peribronchiolar and interstitial fibrosis. PFTs show obstruction but may be restrictive when there is progression of fibrosis. Common HRCT findings are ground-glass opacities, mosaicism, endobronchial wall thickening and nodules. Reported 5 year survival is 83%. Treatment options include observation or trial of inhaled or systemic corticosteroids. Octreotide/somatostatin analogs have been suggested but evidence is lacking. Patients with severe respiratory symptoms should be evaluated for lung transplantation.