A 74-year-old man presented for admission to a long-term care facility. A chest radiograph revealed a right middle lobe density that had not changed in five years (see the accompanying radiograph). The patient was afebrile and had an occasional dry cough. Bronchoscopy was unremarkable; cultures for acid-fast bacilli and fungi were negative, and cytology was significant only for “foamy macrophages.” The patient's medical history was significant for gastroesophageal reflux, hypertension, congestive heart failure and chronic constipation. Current medications included digoxin (Lanoxin), diltiazem (Cardizem) and daily oral mineral oil.
The answer is C: lipoid pneumonia. Exogenous lipoid pneumonia is a rare inflammatory reaction resulting from chronic aspiration of oil or fat. It is most commonly associated with the use of oral mineral oil, and nose drops that contain paraffin. It has also been reported to occur following injection of oils.1 The most common symptom of lipoid pneumonia is chronic cough; however, the disease is often discovered incidentally on a routine chest radiograph.2 Radiographic findings include either a multilobar consolidating infiltrate or a well-circumscribed homogenous infiltrate in a lower lobe,3 as is seen in this patient's radiograph. Computed tomography may demonstrate a mass with decreased attenuation.4 The diagnosis is confirmed by obtaining sputum or bronchial washings containing lipid-laden alveolar macrophages. Treatment includes the immediate cessation of the oil product.3
Of the remaining multiple choice answers, the smooth border and solitary nature of this lesion are more suggestive of a primary lung tumor than of metastatic carcinoma. However, both the chronicity and the bronchoscopic findings effectively eliminate these diagnoses. A lesion associated with postprimary or reactivation tuberculosis is most often seen in the apical lobes. Lung abscess typically causes a cavitary lesion with an air-fluid level. The absence of either a fever or a productive cough makes this diagnosis unlikely.