Pneumonia due to an infectious etiology is by far the most likely diagnosis in a patient presenting with fever, cough, and focal consolidation. However, a number of noninfectious conditions may mimic pneumonia (Table 33–2) including foreign body aspiration, heart failure, malignancy (e.g., lymphoma), atelectasis, pulmonary embolus, pulmonary hemorrhage (e.g., idiopathic pulmonary hemosiderosis, Wegner's granulomatosis), and sarcoidosis. Collagen vascular diseases including systemic lupus erythematosus, scleroderma, and rheumatoid arthritis may cause interstitial lung disease with pulmonary fibrosis. Other causes of interstitial lung disease include environmental irritants such as noxious gases, radiation, and certain drugs. Hydrocarbons (e.g., gasoline, kerosene, charcoal lighter fluid) may be accidentally ingested by young children, leading to a secondary pneumonitis. Congenital lung anomalies, which can lead to pneumonia, include pulmonary sequestration, congenital lobar emphysema, and congenital cystic adenomatoid malformations.