Pulmonary eosinophilic granuloma is the pulmonary form of histiocytosis X, a disease characterized by proliferation of Langerhans’ cells.
The radiographic findings are diffuse, reticular, nodular, or reticulonodular infiltrates predominantly in the middle and upper lung fields. Unlike patients with most ILDs, patients with pulmonary eosinophilic granuloma have normal lung volumes.
The disease is associated with smoking and has a highly variable course, frequently with spontaneous remission. Patients are at increased risk of spontaneous and often recurrent pneumothoraces. Lymphangioleiomyomatosis is a disease of premenopausal women that is characterized by proliferation of smooth muscle in the walls of the pulmonary lymphatics and venules and causes obstruction and ILD. Lymphangioleiomyomatosis may produce chylous pleural effusions and alveolar hemorrhage and is a progressive, fatal disease. Because it menopausal women and is accelerated during pregnancy, and because the pathologic cells resemble uterine muscle cells, hormonal manipulation has been used as therapy but without much Success. Pulmonary alveolar proteinosis is a disorder in which the alveoli fill with protein and phospholipid material similar to surfactant. The origin of pulmonary alveolar proteinosis is unknown, but it is thought to result from an unknown inhaled insult. In healthy lungs, surfactant is cleared by macrophages. Material like that found in pulmonary alveolar proteinosis is seen in the alveoli of patients with acute silicosis, a situation in which macrophage function is known to be inhibited. Investigators have postulated that the basic defect in pulmonary alveolar proteinosis is the inability of macrophages to clear surfactant. A genetically engineered mouse that does not express the gene that encodes granulocyte-monocyte colony stimulating factor(GM-CSF) has been found to develop pulmonary alveolar proteinosis, and studies of therapy with this factor in patients with pulmonary alveolar proteinosis are currently under way.
Traditionally, these patients have been treated by bilateral whole-lung lavage to”wash out” the abnormal material filling alveoli. This intervention dramatically improves oxygenation in the short term, but the course of the disease is variable. In some patients, the disease resolves after only one lavage, whereas in others, the disease progresses to severe fibrosis in spite of repeated lavage.
Bronchiolitis obliterans with organizing pneumonia is thought to be a response to lung injury resulting from infections, inhaled toxin, or autoimmune disease.