A 62-year-old automobile worker presents with gradually worsening exertional dyspnea over the preceding several months. Recently, he has noticed right pleuritic chest pain. He has hypertension, well controlled on amlodipine 5 mg a day. He takes no other medications. He has never noticed cough or wheezing while at work. He worked for 15 years in construction and demolition and for 20 years thereafter in the service department of an automotive dealership. He denies fever, chills, or night sweats. On physical examination, he is in no respiratory distress but has right basilar dullness. His finger oximetry reads 96% on room air. Chest x-ray reveals a moderate right pleural effusion and lateral pleural thickening on both sides. Thoracentesis shows reddish fluid, which on formal analysis, is an exudate with 45,000 RBCs/hpf. Cytology is negative. What is the most likely explanation for this patient’s symptoms?
A. Drug induced interstitial lung diseaseOccupational lung disease is an important branch of pulmonology, and new inhaled workplace toxins are being described every year. A detailed occupational history and knowledge of potential culprits are, therefore, critical in patients with unexplained lung disease. This patient’s exposure history is suggestive of asbestos related disease; bilateral pleural thickening (often calcified, a finding especially evident on CT scan) indicates prior asbestos exposure. Occasionally, the pleural involvement is associated with a pleural effusion (often with an elevated red cell count) called benign asbestos pleural effusion (BAPE). “Benign” distinguishes this syndrome from malignant effusions due to lung cancer or mesothelioma, both of which occur with increased frequency in asbestosis. Progressive debility from an interstitial lung disease (which worsens even after asbestos exposure has ceased) may occur in asbestosis, but this patient’s physical examination and chest x-ray do not suggest interstitial disease. Medications, especially nitrofurantoin and cancer chemotherapeutic agents, can cause interstitial lung disease, but amlodipine has not been reported to do so. Tuberculosis occurs with increased frequency in silicosis, not in asbestosis. Although TB can cause a bloody pleural effusion, this patient does not have the systemic symptoms that usually accompany TB. Hypersensitivity pneumonitis is an important cause of occupational lung disease, but it is caused by exposure to organic materials such as thermophilic actinomycetes (farmer’s lung). In addition, hypersensitivity pneumonitis usually causes acute symptoms (including fever) at time of exposure. Occupational asthma is an important category, since continued exposure can lead to irreversible changes. Isocyanates in automobile paints are an important cause of occupational asthma, but the symptoms are usually more acute and associated with wheezing on physical examination. Hypersensitivity pneumonitis and occupational asthma do not cause pleural disease.