A 53-year-old man comes to the office due to an 8-month history of progressive shortness of breath that peaks during strenuous activity. Several of his coworkers have experienced similar symptoms. His medical history includes hypertension and type 2 diabetes mellitus. Pulmonary examination reveals diffuse fine crackles. Chest x-ray reveals nodular densities in both lungs that are most prominent in the apical regions. Calcification of the hilar lymph nodes is also seen. Bronchoscopy with transbronchial biopsy of a calcified node is performed, and polarized microscopy shows birefringent particles surrounded by dense collagen fibers. This patient most likely has a history of exposure to which of the following substances?

Question

A 53-year-old man comes to the office due to an 8-month history of progressive shortness of breath that peaks during strenuous activity.  Several of his coworkers have experienced similar symptoms.  His medical history includes hypertension and type 2 diabetes mellitus.  Pulmonary examination reveals diffuse fine crackles.  Chest x-ray reveals nodular densities in both lungs that are most prominent in the apical regions.  Calcification of the hilar lymph nodes is also seen.  Bronchoscopy with transbronchial biopsy of a calcified node is performed, and polarized microscopy shows birefringent particles surrounded by dense collagen fibers.  This patient most likely has a history of exposure to which of the following substances?

Quizplus · Accepted Answer

This middle-aged patient with dyspnea on exertion, nodular densities on x-ray, calcified hilar lymph nodes, and birefringent particles on biopsy has silicosis. Silicosis is a form of pneumoconiosis (ie, a type of interstitial lung disease caused by inhalation of mineral dust). Inhaled crystalline silica, typically due to industrial exposure (eg, mining, sand blasting), is toxic to alveolar macrophages and promotes the formation of intrapulmonary free radicals, leading to progressive lung injury and interstitial collagen deposition. Histologically, silicosis is characterized by birefringent silicate particles within dense, whorled collagenous nodules surrounded by dust-laden macrophages. Silicosis is often initially asymptomatic but can present with dyspnea on exertion and productive cough, typically 10-20 years after initial exposure. Radiography varies based on disease progression; simple silicosis typically demonstrates numerous small, rounded nodules predominant in the upper lobes that may rarely coalesce to form mass-like upper lobe fibrosis (progressive massive fibrosis). Calcification of the rim of hilar nodes (eggshell calcification) may also be seen. (Choice A) Asbestosis can present with dyspnea on exertion, but chest x-ray is more likely to reveal an interstitial pattern of involvement most prominent in the lower zones. Pleural plaques may also be noted. Histology shows ferruginous bodies featuring fusiform rods with a translucent asbestos center and a golden-brown iron coating. (Choice B) Berylliosis may present with dyspnea and ill-defined nodular or irregular opacities on chest x-ray. Histology reveals noncaseating epithelioid granulomas without obvious associated particles. (Choice C) Coal worker's pneumoconiosis can present with exertional dyspnea and nodular interstitial opacities on chest x-ray. Histology of nodal and perilymphatic lung tissue shows accumulations of black, carbon-laden macrophages (coal macules). (Choice D) Inhalation of organic dusts can cause hypersensitivity pneumonitis. Patients have exertional dyspnea and diffuse nodular interstitial infiltrates on chest x-ray. Histology of nodal tissue may reveal noncaseating granulomas. Educational objective: Silicosis is characterized by dyspnea and productive cough occurring years after inhalational exposure to crystalline silica. Histologically, it is characterized by birefringent silicate particles within dense, whorled collagenous nodules surrounded by dust-laden macrophages. Radiography typically demonstrates numerous small, rounded nodules predominant in the upper lobes; calcification of the rim of hilar nodes (eggshell calcification) may also be seen. __________ References: Pneumoconiosis. (http://www.ncbi.nlm.nih.gov/pubmed/23708110) Occupational respiratory disease in mining. (http://www.ncbi.nlm.nih.gov/pubmed/15289586)

A 53-Year-Old Man Comes to the Office Due to an 8-Month