A 60-year-old man comes to the physician with a 2-year history of slowly progressive dyspnea on exertion. Over the last 6 months, he has had a frequent nonproductive cough, malaise, and a 4.5-kg (10-lb) weight loss. He ran and biked every day prior to developing these symptoms. His past medical history includes hypertension treated with hydrochlorothiazide. Prior to retiring 3 years ago, he worked in a rock quarry for 25 years. He has a 30-pack-year smoking history and quit 10 years ago,
His temperature is 36.7° C (98° F), blood pressure is 138/88 mm Hg, pulse is 88/min, and respirations are 16/min. Pulse oximetry is 92% at rest on room air. Physical examination shows a thin man in no acute distress. Jugular venous pressure is estimated at 5 cm. Lung examination is notable for fine crackles in the upper- and mid-lung fields. The remainder of the examination is normal.
Results of pulmonary function tests are as follows:

Chest x-ray reveals bilateral interstitial infiltrates in the upper lung fields. High-resolution computed tomography of the chest demonstrates diffuse micronodules and fibrotic lung changes in the upper lobes bilaterally.
Which of the following is the most likely cause of the patient's symptoms?

Question

A 60-year-old man comes to the physician with a 2-year history of slowly progressive dyspnea on exertion.  Over the last 6 months, he has had a frequent nonproductive cough, malaise, and a 4.5-kg (10-lb) weight loss.  He ran and biked every day prior to developing these symptoms.  His past medical history includes hypertension treated with hydrochlorothiazide.  Prior to retiring 3 years ago, he worked in a rock quarry for 25 years.  He has a 30-pack-year smoking history and quit 10 years ago,
His temperature is 36.7° C (98° F), blood pressure is 138/88 mm Hg, pulse is 88/min, and respirations are 16/min.  Pulse oximetry is 92% at rest on room air.  Physical examination shows a thin man in no acute distress.  Jugular venous pressure is estimated at 5 cm.  Lung examination is notable for fine crackles in the upper- and mid-lung fields.  The remainder of the examination is normal.
Results of pulmonary function tests are as follows:

Chest x-ray reveals bilateral interstitial infiltrates in the upper lung fields.  High-resolution computed tomography of the chest demonstrates diffuse micronodules and fibrotic lung changes in the upper lobes bilaterally.
Which of the following is the most likely cause of the patient's symptoms?

Quizplus · Accepted Answer

11ec193a_98da_db34_853d_abc21769e316_MD0002_00 This patient's presentation (cough, dyspnea on exertion, lung examination, and history of quarrying) suggests silicosis, a lung disease due to crystalline silica (eg, quartz, cristobalite, and tridymite) inhalation. Silicosis is usually due to occupational exposure and may present as an acute, chronic, or accelerated form depending on the duration of exposure to silica. Respiratory protective devices have variable effectiveness in preventing disease, and it can occur even in workers who use personal respiratory protection. Chronic silicosis (most common) usually presents within 10-30 years of exposure with chronic cough, dyspnea on exertion, and fine or coarse crackles (with or without wheezing) on lung examination. Chest imaging usually shows rounded and nodular opacities < 10 mm in diameter in the mid- to upper-lung zones. These nodules may coalesce in some patients to form progressive massive fibrosis (PMF) and result in retracted hila, upper-lobe fibrosis, and lower-lobe hyperinflation. Accelerated silicosis is due to high silica exposure and presents within 10 years of exposure with clinical findings similar to those of chronic silicosis but with a higher PMF risk. Diagnosis is suggested by clinical findings, occupational history, chest imaging, and absence of other etiologies. Spirometry usually shows mixed obstructive and restrictive impairment with decreased FEV₁ and FEV₁/FVC ratio. PMF is associated with a sharper decline in pulmonary function tests. Lung biopsy may be needed when the diagnosis is uncertain. Silicosis is associated with increased risk of lung cancer, mycobacterial infection, autoimmune disorders, airflow obstruction, and chronic bronchitis. Patients should undergo screening for active latent tuberculosis at the time of diagnosis, with PPD reaction > 10 mm considered positive. Treatment is mainly supportive (eg, bronchodilators and supplemental oxygen) with possible lung transplantation for end-stage silicosis. (Choice A) Asbestosis is more common in plumbers, carpenters, electricians, and janitors. Patients usually present 20-30 years after initial exposure with chronic dyspnea. Spirometry usually reveals a strictly restrictive pattern with no airflow obstruction, and chest imaging usually shows pleural plaques instead of upper-lung zone abnormalities. (Choice B) Although patients with silicosis are at an increased risk of lung cancer, this patient's chest imaging showing bilateral interstitial fibrosis and micronodules is not suggestive of bronchogenic carcinoma. Larger (> 1 cm) nodules are expected with lung cancer. (Choice C) In idiopathic pulmonary fibrosis lung functions tests usually show a restrictive pattern. Idiopathic pulmonary fibrosis is typically a disease of the lower lung fields, and the diagnosis requires lack of an alternative explanation such as silica or asbestos exposure. High-resolution chest CT shows characteristic peripheral and bibasilar opacities with honeycombing and traction bronchiectasis. honeycombing and traction bronchiectasis (Choice D) Up to 90% of patients with sarcoidosis present at age 10-40 years. Although sarcoidosis can cause very similar findings, including involvement of the upper lobes, it is somewhat less likely given this patient's occupational exposure and age. Educational objective: Silicosis is usually due to occupational exposure and may present with chronic cough and dyspnea on exertion. Chest imaging reveals multiple micronodules, predominately in the upper lung fields. Silicosis is associated with an increased incidence of lung cancer and active tuberculosis, which should be screened for and appropriately treated at the time of diagnosis. __________ References: Occupational respiratory disease in mining. (http://www.ncbi.nlm.nih.gov/pubmed/15289586) Silicosis. (http://www.ncbi.nlm.nih.gov/pubmed/22534002)

A 60-Year-Old Man Comes to the Physician with a 2-Year