A 66-year-old man comes to the office due to 3 months of slowly worsening nonproductive cough and shortness of breath. He has also had night sweats, excessive fatigue, and sharp, episodic right-sided chest pain. The patient has lost approximately 5 kg (11 lb) during this period. He has a history of hypertension and takes chlorthalidone. He has smoked a half-pack of cigarettes daily for the past 50 years. The patient worked in a shipbuilding factory until his early 40s and then began working in the automobile industry. Temperature is 36.7 C (98 F), blood pressure is 130/80 mm Hg, pulse is 84/min, and respirations are 14/min. No jugular venous distension or lymphadenopathy is present. There is dullness to percussion and decreased breath sounds over the right lower chest. Heart sounds are normal with no murmur. The abdomen is soft and nontender with no hepatosplenomegaly. No edema is present. Chest imaging reveals a moderate right-sided pleural effusion with irregular pleural thickening and calcifications, but no lung parenchymal abnormalities. A thoracentesis is performed and yields serosanguineous pleural fluid; pleural fluid analysis reveals the following: Which of the following is the most likely cause of this patient's pleural effusion?

Question

A 66-year-old man comes to the office due to 3 months of slowly worsening nonproductive cough and shortness of breath.  He has also had night sweats, excessive fatigue, and sharp, episodic right-sided chest pain.  The patient has lost approximately 5 kg (11 lb) during this period.  He has a history of hypertension and takes chlorthalidone.  He has smoked a half-pack of cigarettes daily for the past 50 years.  The patient worked in a shipbuilding factory until his early 40s and then began working in the automobile industry.  Temperature is 36.7 C (98 F), blood pressure is 130/80 mm Hg, pulse is 84/min, and respirations are 14/min.  No jugular venous distension or lymphadenopathy is present.  There is dullness to percussion and decreased breath sounds over the right lower chest.  Heart sounds are normal with no murmur.  The abdomen is soft and nontender with no hepatosplenomegaly.  No edema is present.  Chest imaging reveals a moderate right-sided pleural effusion with irregular pleural thickening and calcifications, but no lung parenchymal abnormalities.  A thoracentesis is performed and yields serosanguineous pleural fluid; pleural fluid analysis reveals the following:  Which of the following is the most likely cause of this patient's pleural effusion?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c1b8_d92b_8f63_6fa9ce78123f_MD0005_00 This patient who worked as a shipbuilder has a pleural effusion and pleural thickening/calcifications raising suspicion for malignant mesothelioma, a neoplasm tightly linked to occupational asbestos exposure. Most cases arise in those who worked in the cement, tile, automobile brake pad, or shipbuilding industries prior to asbestos control initiatives. Tumors primarily form on the pleura, but other mesothelial surfaces can be affected including the peritoneum, tunica vaginalis, and pericardium. Malignant pleural mesotheliomas tend to present after weeks or months of nonspecific symptoms including cough, dyspnea, weight loss, night sweats, and fatigue. Pleural effusion is almost always present and is typically noted on physical examination (eg, dullness to percussion) and chest x-ray. Pleural fluid analysis often shows an exudative effusion that tends to have low pH and glucose levels; cytology may be negative. Most patients also have pleural thickening, calcifications, and/or mass. Definitive diagnosis can sometimes (~35%) be made using thoracentesis with cytology, but most cases require video-assisted thorascopic biopsy or open thoracotomy. Treatment with surgery, systemic chemotherapy, and/or radiotherapy is often palliative, but cure is uncommon. Median survival is 9-13 months. (Choice A) Chronic silicosis is also an occupational disease that primarily affects the lung. Miners, sandblasters, foundry workers, and masons are most commonly affected. Chest x-ray usually shows upper lobe nodules and lower lobe emphysema; pleural thickening and calcifications are not typical features of this disease. (Choice C) Non-Hodgkin lymphoma is a hematologic malignancy, which often presents with B symptoms, lymphadenopathy, hepatosplenomegaly, and cytopenias. Pulmonary complaints can occur due to mediastinal lymphadenopathy, but pleural thickening and nodules would be uncommon. (Choice D) Classic findings seen on pleural fluid analysis of rheumatoid pleural effusions include leukocytes <5,000/mm³, glucose <60 mg/dL, pH <7.3, and high LDH. These results are similar to those seen in this patient with mesothelioma; however, most patients with rheumatoid arthritis will also have joint manifestations (eg, polyarticular arthritis, significant morning stiffness). (Choice E) Thoracic duct obstruction can cause chylothorax, which often presents with subacute pulmonary symptoms due to pleural effusion. The diagnosis is usually suspected when the pleural fluid triglyceride level is >110 mg/dL (unlike in this patient). In addition, pleural thickening and calcification would be atypical. Educational objective: Malignant pleural mesothelioma is closely associated with occupational asbestos exposure and frequently presents with subacute pulmonary symptoms. Chest imaging usually shows pleural effusion and pleural thickening, calcifications, or mass. Diagnosis is typically made by thoracentesis with cytology (~35% sensitivity), video-assisted thorascopic biopsy, or open thoracotomy.

A 66-Year-Old Man Comes to the Office Due to 3