eMedicine Specialties > Pulmonology > Occupational Lung Diseases

Silicosis: Differential Diagnoses & Workup

Author: Basil Varkey, MD, FCCP, Professor, Department of Internal Medicine, Division of Pulmonary and Critical Care, Medical College of Wisconsin; Consulting Pulmonologist, Froedtert Memorial Lutheran Hospital
Coauthor(s): Anita B Varkey, MD, Assistant Professor, Department of Medicine, Loyola University Medical Center; Associate Program Director, Internal Medicine Residency; Medical Director, General Internal Medicine Clinic, Loyola Outpatient Center
Contributor Information and Disclosures

Updated: Apr 16, 2008

Differential Diagnoses

Asbestosis
Pulmonary Alveolar Proteinosis
Chronic Obstructive Pulmonary Disease
Pulmonary Fibrosis, Idiopathic
Coal Worker's Pneumoconiosis
Sarcoidosis
Hypersensitivity Pneumonitis
Wegener Granulomatosis
Miliary Tuberculosis

Other Problems to Be Considered

Pulmonary tuberculosis
Rheumatoid lung nodules
Metastatic lung cancer

Workup

Laboratory Studies

  • Although various serologic abnormalities have been noted in patients with silicosis, they are not diagnostic of the disease, and tests to detect these abnormalities are not indicated routinely (see Other Tests).
  • Humoral immune system abnormalities observed in silicosis include increased incidence and titer of rheumatoid factor, antinuclear antibodies, and immune complexes. No consistent abnormality is noted in the cell-mediated immune system.

Imaging Studies

  • Chest radiograph
    • Radiographic studies of the chest are essential to the diagnosis of silicosis. While some chest radiographic findings of silicosis may be nonspecific, others are sufficiently characteristic of the disease.
    • Bilateral alveolar filling and a ground-glass appearance mimicking alveolar proteinosis are observed in silicoproteinosis.
    • Simple silicosis manifests as multiple small (<10 mm) nodules that are scattered diffusely throughout the lungs but may be more prominent in the upper lung fields. These radiographic findings have been found to correlate well with pathologic findings. Chest radiographic findings in persons with simple silicosis have a high degree of sensitivity and specificity. Calcification of the hilar lymph nodes, particularly in the rim of the nodes (ie, eggshell calcification) is very characteristic of silicosis. However, eggshell calcifications are observed only in a minority of cases of silicosis. Other causes of eggshell calcification include sarcoidosis, histoplasmosis, and irradiation. Rarely, the pulmonary nodules also may show calcification.
    • Complicated silicosis (also known as PMF) manifests as bilateral upper lobe masses, which are formed by the coalescence of nodules. Cavitation may be seen. As these masses retract toward the hilum because of fibrosis, the lower lung fields may appear overinflated. Hilar calcifications may be present.
  • CT scan
    • A high-resolution CT scan of the chest may be more sensitive than chest radiography in discerning the nodules of simple silicosis.
    • In progressive massive fibrosis, a CT scan provides more detail of emphysematous changes, pleural thickening, and the confluent masslike lesions (eg, the presence of cavitation) than a chest radiograph. Although cavitation in silicosis can occur without a mycobacterial infection, such a possibility should be considered when cavitation is observed.
    • Although pleural effusions are quite rare, pleural thickening is not an unusual finding.

Other Tests

  • Pulmonary function tests
    • Pulmonary function test results may be normal in simple silicosis. However, silicosis is associated with an excessive decline in lung function.
    • In more advanced disease, airflow obstruction or a mixed pattern of obstruction and restriction is observed.
    • In smokers with airflow obstruction, separating the effect of silicosis from the confounding factor of tobacco smoke is difficult.
    • Progressive massive fibrosis causes severe restriction, decreased compliance, and hypoxemia.
  • A tuberculin skin test using purified protein derivative (PPD) is indicated in all persons with silicosis. If the test result is positive (ie, 10 mm or more of induration at the site), treatment for latent or active infection is indicated. In individuals who have a positive skin test result, sputum samples should be examined for acid-fast bacilli (AFB) by microscopy and cultured for AFB to identify active disease.

Procedures

  • Bronchoscopy rarely is needed. The rare indication is in a cavitary or mass lesion when mycobacterial disease or lung cancer is suspected and examination of sputum samples is nondiagnostic.

Histologic Findings

Examination of lung tissue very seldom is necessary because the diagnosis of silicosis is based on history of exposure, symptoms, physical examination findings, and chest radiographic appearance.

The initial histopathologic changes of silicosis are pigmented macrophages and reticulin fibers in peribronchial, paraseptal, and perivascular areas.

The characteristic histopathologic finding is the silicotic nodule mostly located near the respiratory bronchiole. The nodule is composed of refractile particles of silica surrounded by whorled collagen in concentric layers, with macrophages, lymphocytes, and fibroblasts in the periphery. Emphysematous blebs surround the silicotic nodule, especially in the subpleural area. Birefringent crystals of silica in the center of a silicotic nodule may be identified by polarized light microscopy. For definitive identification, scanning electron microscopy combined with x-ray spectroscopy may be needed.

In PMF, the masslike areas may show cavitation caused by a necrotic process.

Acute silicosis silicotic nodules are seldom seen and the histology is similar to pulmonary alveolar proteinosis with alveolar filling with proteinaceous material that stains with periodic acid-Schiff stain.

More on Silicosis

Overview: Silicosis
Differential Diagnoses & Workup: Silicosis
Treatment & Medication: Silicosis
Follow-up: Silicosis
References
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References

  1. Caplan A, Payne RB, Withley JL. A broadened concept of Caplan's syndrome related to rheumatoid factors. Thorax. 1962;17:205-209.

  2. Centers for Disease Control and Prevention. Silicosis in dental laboratory technicians--five states, 1994-2000. MMWR Morb Mortal Wkly Rep. Mar 12 2004;53(9):195-7. [Medline].

  3. Goodman GB, Kaplan PD, Stachura I, Castranova V, Pailes WH, Lapp NL. Acute silicosis responding to corticosteroid therapy. Chest. Feb 1992;101(2):366-70. [Medline].

  4. Sharma SK, Pande JN, Verma K. Effect of prednisolone treatment in chronic silicosis. Am Rev Respir Dis. Apr 1991;143(4 Pt 1):814-21. [Medline].

  5. Rosenman KD, Moore-Fuller M, Reilly MJ. Connective tissue disease and silicosis. Am J Ind Med. Apr 1999;35(4):375-81. [Medline].

  6. Mulloy KB. Silica exposure and systemic vasculitis. Environ Health Perspect. Dec 2003;111(16):1933-8. [Medline].

  7. American Thoracic Society. Targeted tuberculin testing and treatment of latent tuberculosis infection. This official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999. This is a Joint Statement of the American Thoracic Society (ATS) and the Centers for Disease Control and Prevention (CDC). This statement was endorsed by the Council of the Infectious Diseases Society of America. (IDSA), September 1999, and the sections of this statement. Am J Respir Crit Care Med. Apr 2000;161(4 Pt 2):S221-47. [Medline].

  8. Arakawa H, Honma K, Saito Y, Shida H, Morikubo H, Suganuma N. Pleural disease in silicosis: pleural thickening, effusion, and invagination. Radiology. Aug 2005;236(2):685-93. [Medline].

  9. Attfield MD, Costello J. Quantitative exposure-response for silica dust and lung cancer in Vermont granite workers. Am J Ind Med. Feb 2004;45(2):129-38. [Medline].

  10. Banks DE, Balaan M, Wang ML. Silicosis in the 1990s, revisited. Chest. Apr 1997;111(4):837-8.

  11. Corbett EL, Churchyard GJ, Clayton T, Herselman P, Williams B, Hayes R. Risk factors for pulmonary mycobacterial disease in South African gold miners. A case-control study. Am J Respir Crit Care Med. Jan 1999;159(1):94-9. [Medline].

  12. Corbett EL, Murray J, Churchyard GJ, Herselman PC, Clayton TC, De Cock KM. Use of miniradiographs to detect silicosis. Comparison of radiological with autopsy findings. Am J Respir Crit Care Med. Dec 1999;160(6):2012-7. [Medline].

  13. Gamble JF, Hessel PA, Nicolich M. Relationship between silicosis and lung function. Scand J Work Environ Health. Feb 2004;30(1):5-20.

  14. Ghio AJ, Kennedy TP, Schapira RM, Crumbliss AL, Hoidal JR. Hypothesis: is lung disease after silicate inhalation caused by oxidant generation?. Lancet. Oct 20 1990;336(8721):967-9. [Medline].

  15. Graham WGB. Quartz and silicosis. In: Banks D, Parker J, eds. Occupational Lung Disease: An International Perspective. New York, NY: Chapman & Hall Medical; 1998:191-212.

  16. Hertzberg VS, Rosenman KD, Reilly MJ, Rice CH. Effect of occupational silica exposure on pulmonary function. Chest. Aug 2002;122(2):721-8. [Medline].

  17. Lapp NL. Pulmonary function and disability. In: Banks D, Parker J, eds. Occupational Lung Disease: An International Perspective. 1998. New York, NY: Chapman & Hall Medical; 1998:17-34.

  18. McDonald JC, McDonald AD, Hughes JM, Rando RJ, Weill H. Mortality from lung and kidney disease in a cohort of North American industrial sand workers: an update. Ann Occup Hyg. Jul 2005;49(5):367-73. [Medline].

  19. National Archives and Records Administration. United States code of federal regulations. 1910.1000. Office of the Federal Register, National Archives and Records Administration; 1994.

  20. Rimal B, Greenberg AK, Rom WN. Basic pathogenetic mechanisms in silicosis: current understanding. Curr Opin Pulm Med. Mar 2005;11(2):169-73.

  21. Valiante DJ, Schill DP, Rosenman KD, Socie E. Highway repair: a new silicosis threat. Am J Public Health. May 2004;94(5):876-80. [Medline].

  22. Wagner GR. Screening and surveillance of workers exposed to mineral dusts. Geneva, World Health Organization. 1996.

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Further Reading

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Keywords

silicosis, pneumoconiosis, pneumoconioses, fibronodular lung disease, work-related illness, mining illness, mining, tunneling, quarrying, drilling, crushing stone, chipping, grinding, sandblasting, cement manufacturing, building construction, occupational hazard, cutting bricks, manufacturing bricks, silica dust, silica exposure

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Contributor Information and Disclosures

Author

Basil Varkey, MD, FCCP, Professor, Department of Internal Medicine, Division of Pulmonary and Critical Care, Medical College of Wisconsin; Consulting Pulmonologist, Froedtert Memorial Lutheran Hospital
Basil Varkey, MD, FCCP is a member of the following medical societies: American Association of Physicians of Indian Origin, American College of Chest Physicians, American Federation for Clinical Research, American Thoracic Society, and Royal College of Physicians
Disclosure: Nothing to disclose.

Coauthor(s)

Anita B Varkey, MD, Assistant Professor, Department of Medicine, Loyola University Medical Center; Associate Program Director, Internal Medicine Residency; Medical Director, General Internal Medicine Clinic, Loyola Outpatient Center
Anita B Varkey, MD is a member of the following medical societies: American College of Physicians and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Medical Editor

Gregory Tino, MD, Director of Pulmonary Outpatient Practices, Associate Professor, Department of Medicine, Division of Pulmonary, Allergy, and Critical Care, University of Pennsylvania Medical Center and Hospital
Gregory Tino, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and American Thoracic Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Om Prakash Sharma, MD, FRCP, FCCP, DTM&H, Professor, Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Southern California Keck School of Medicine
Om Prakash Sharma, MD, FRCP, FCCP, DTM&H is a member of the following medical societies: American Academy of Allergy Asthma and Immunology, American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, American Osler Society, American Thoracic Society, New York Academy of Medicine, and Royal Society of Medicine
Disclosure: Keck School of Medicine, USC None None

CME Editor

Timothy D Rice, MD, Associate Professor, Departments of Internal Medicine and Pediatrics and Adolescent Medicine, Saint Louis University School of Medicine
Timothy D Rice, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Physicians
Disclosure: Nothing to disclose.

Chief Editor

Zab Mosenifar, MD, Director, Division of Pulmonary and Critical Care Medicine, Director, Women's Guild Pulmonary Disease Institute, Executive Vice Chair, Department of Medicine, Cedars Sinai Medical Center; Professor of Medicine, David Geffen School of Medicine at UCLA
Zab Mosenifar, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, and American Thoracic Society
Disclosure: Nothing to disclose.

 
 
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