A number of interstitial lung diseases of unknown etiology have characteristic histology, clinical features, or presentation and thus are considered unique diseases, including Eosinophilic pulmonary diseases Lymphangioleiomyomatosis Pulmonary alveolar proteinosis Pulmonary Langerhans cell histiocytosis (granulocytosis) Sarcoidosis In up to 30% of patients who have interstitial lung diseases with no clear cause, the disorders are distinguished primarily by characteristic histopathologic features; these disorders are termed the idiopathic interstitial pneumonias.