Airspace Diseases and Pulmonary Nodules

Diseases that present as lung nodules and airspace opacities include cryptogenic organizing pneumonia, eosinophilic pneumonia, allergic bronchopulmonary aspergillosis, lipoid pneumonia, and sarcoidosis. The most important diagnostic decision in cryptogenic organizing pneumonia is the exclusion of any other potential causes. The secondary causes of organizing pneumonia include infectious processes, exposures to chemical or fumes, antibiotics, connective tissue diseases, radiation, and chemotherapy including new checkpoint inhibitors. The eosinophilic disorders comprise rare infiltrative parenchymal lung diseases characterized by the presence of eosinophils in the interstitium and alveolar space with conservation of the lung architecture. Allergic bronchopulmonary aspergillosis occurs in patients with prior bronchial disease. Following exposure to Aspergillus, bronchial disease–associated mucus plugs produce a complex chronic immune and inflammatory reaction inside the bronchi and in the lung parenchyma with secondary damage and impairment of the normal mucociliary clearance. Lipoid pneumonia is also known as cholesterol pneumonia, paraffinoma, or golden pneumonia. This unusual type of pneumonia can be seen predominantly in bedridden patients; however, it can occur in any age group. The cause of lipoid pneumonia may be either endogenous or exogenous. Endogenous causes may include gastroesophageal reflux, while exogenous causes may include aspiration of substances such as mineral or vegetable oil, petroleum jelly, or in some cases radiographic contrast media. Pulmonary sarcoidosis is a multisystemic granulomatous syndrome of unknown origin, which affects the lungs in 90% of cases, although any organ can be compromised during the course of the disease. It also has a varied clinic presentation, from asymptomatic incidentally found to progressive life-threating involvement of the affected organ, such as lung fibrosis.