Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 70-year-old man is evaluated for a 3-month history of night sweats, weight loss, and increasing cough. He is a retired miner, and his medical history is significant for a diagnosis of pulmonary silicosis made 15 years ago based on exposure history and characteristic chest radiographic findings. He is a lifelong nonsmoker.
On physical examination, temperature is 37.9 °C (100.2 °F), blood pressure is 120/65 mm Hg, pulse rate is 84/min, and respiration rate is 22/min. Pulmonary examination reveals diffuse inspiratory crackles throughout all lung zones, unchanged from previous examinations.
Pulmonary function tests demonstrate mild obstruction with no change from 1 year ago. Chest radiograph shows multiple small nodules that appear throughout all lung zones but are upper-lobe predominant. There is no significant change in comparison with previous imaging studies.
Which of the following is the most appropriate next step in management?
A: High-resolution CT of the chest
B: Lung biopsy
C: Prednisone
D: Tuberculosis testing
MKSAP Answer and Critique
The correct answer is D: Tuberculosis testing.
The most appropriate next step in management is evaluation for tuberculosis with purified protein derivative testing and sputum testing for acid-fast bacilli. Silicosis is a spectrum of pulmonary disease related to inhalation of crystalline silicon dioxide (silica). Silica is the most abundant mineral on earth, and the most common form is quartz. Any occupation that disturbs the earth’s crust or uses or processes silica-containing rock or sand has potential risks. A number of other medical conditions are associated with silicosis and are believed to be due to immune dysfunction induced by silicon exposure. This includes an increased susceptibility to tuberculosis and autoimmune diseases such as systemic sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. A recent investigation by the Centers for Disease Control and Prevention examined silicosis mortality rates associated with respiratory tuberculosis between the years of 1968 and 2006. Of the reported deaths, tuberculosis was on 14% of the death certificates. Seventy-three percent of these patients were older than 65 years, and greater than 99% were male. There has been a steady decline in the total number of deaths related to silicosis and concomitant tuberculosis infection. This is likely attributable to prevention and control measures to prevent silica dust exposure as well as to appropriately treat and contain tuberculosis.
A high-resolution chest CT would provide more detailed structural information concerning this patient’s lung disease and might be abnormal if he has tuberculosis, but it would not be the appropriate next study to evaluate for that potential diagnosis.
In patients with a known exposure and characteristic radiographic findings, lung biopsy is generally not needed to establish the diagnosis of silicosis. Additionally, in this patient with a long-standing diagnosis, stable clinical course, and no radiographic changes from his stable baseline, a lung biopsy is not currently indicated.
Corticosteroids have been used in some trials to attempt to modulate the immune reaction to silica and may be of some benefit, particularly in patients with acute or severe disease; however, it is not considered an established therapy for chronic silicosis. In addition, it would be inappropriate therapy until tuberculosis is excluded as a cause of this patient’s systemic symptoms.
Key Point
- Silicosis is a spectrum of pulmonary disease related to inhalation of crystalline silicon dioxide (silica), and it is associated with an increased risk for tuberculosis.
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