A 72-year-old man is evaluated for a 2-year history of cough and a 1-year history of increasing dyspnea. He describes the cough as nonproductive, and his shortness of breath is worse with exertion. He does not have chest pain, orthopnea, paroxysmal nocturnal dyspnea, or any other symptoms. Medical history is otherwise unremarkable. He has a 15-pack-year smoking history but quit 40 years ago. He worked as a construction worker for 40 years. He takes no medications.
On physical examination, temperature, blood pressure, and pulse rate are normal; respiration rate is 18/min. Oxygen saturation breathing ambient air is 96%. BMI is 24. Pulmonary examination reveals inspiratory crackles at the bases bilaterally. Cardiac examination is normal. The remainder of the physical examination is unremarkable.
Chest radiograph shows increased interstitial markings at the bases; calcified parietal pleural plaques are noted bilaterally. High-resolution CT shows bilateral peripheral- and basal-predominant septal line thickening with evidence of honeycomb change at the bases. Pulmonary function tests reveal an FEV1 of 70% of predicted, an FVC of 75% of predicted, an FEV1/FVC ratio of 85%, and a DLCO of 65% of predicted.
Which of the following is the most likely diagnosis?
C. Hypersensitivity pneumonitis
D. Idiopathic pulmonary fibrosis
MKSAP Answer and Critique
The correct answer is A. Asbestosis.
The most likely diagnosis is asbestosis. The extent of asbestos exposure correlates with risk for disease, with the most common occupational exposures occurring in the construction, automotive servicing, and shipbuilding industries. This patient has a significant exposure history from his construction work for 40 years. History regarding exposure can often be difficult to obtain; however, asking questions regarding limited visibility in the work place due to particulate matter as well as failure to wear protective equipment can suggest an extensive exposure. The latency period between exposure and development of asbestosis is prolonged (15-35 years) and is consistent with this patient’s clinical picture. This patient has evidence of fibrosis on lung examination and no evidence to suggest an alternative diagnosis. Pulmonary function testing is consistent with restriction, and chest imaging demonstrates fibrosis and bilateral pleural plaques, which provide evidence of past asbestos exposure. The history, physical examination, and imaging findings are all consistent with diffuse parenchymal lung disease due to asbestosis.
This patient’s presentation and laboratory studies are less consistent with COPD. He does not have an extensive tobacco use history, and his physical examination findings are not suggestive of airflow obstruction, which is confirmed by pulmonary function studies. Therefore, COPD is an unlikely cause of this patient’s symptoms.
Hypersensitivity pneumonitis in its chronic form may present with indolent symptoms of cough and dyspnea, and it would occur secondary to exposure to an antigen that leads to an immune response. This patient has no exposures other than asbestos. In addition, imaging findings in individuals with hypersensitivity pneumonitis are mid- and upper-lung predominant. Therefore, hypersensitivity pneumonitis is not the most likely diagnosis in this patient.
Idiopathic pulmonary fibrosis (IPF) is the most common form of idiopathic interstitial pneumonia and commonly affects individuals later in life. It is associated with a history of increased dust exposure, and it is also a diagnosis of exclusion. However, this patient has a clear history of asbestos exposure, which is associated with the development of pulmonary fibrosis and precludes a diagnosis of IPF. This is particularly important because the prognosis for patients with asbestosis is better than for those with well-documented IPF.
- Asbestosis is characterized by slowly progressive pulmonary fibrosis; the presence of pleural plaques confirms asbestos exposure.
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