A. Definition and Characteristics [1]

1. Non-neoplastic lung reaction to mineral or organic dusts
2. Also includes lung reactions to inorganic particulates and chemical fumes
3. Interstitial, fibrotic type lung disease often develops
   1. Fibrotic diseases are most common reaction to dusts
   2. Hypersensitivity reactions with granuloma formation also occur
   3. Inhalation fever with peripheral leukocytosis and no lung pathology also occurs
4. Progressive shortness of breath and cardiopulmonary failure may ensue
5. Lung Transplantation may be required

B. Classification

1. Mineral Dusts [2]
   1. Silica
   2. Coal Dust
   3. Asbestos
   4. Beryllium
   5. Iron Oxides
   6. Barium Sulfate
   7. Tin Oxide
   8. Cobalt
   9. Talc
   10. Kaolin
2. Organic Dusts
   1. Moldy Hay - Farmer's Lung
   2. Bird Droppings - Bird-Breeder's Lung
3. Nylon Fibers - Flock Worker's Lung [4]
4. Bronchial Hyperreactivity
5. Chemical Fumes
6. Caplan's Syndrome - coexistance of rheumatoid arthritis and pneumoconiosis

C. Risks for Development of Pneumoconiosis

1. Amount of dust retained in lung and airways
2. Size, shape, buoyancy of particles
   1. Most dangerous particles are 1 to 5µm in diameter
   2. These particles reach terminal small airways and air sacs
3. Particle solubility and physiochemical reactivity
4. Additive effects of other agents (cigarette smoking)

D. Coal Workers' Pneumoconiosis (CWP)

1. Variants
   1. Anthracosis - carbon pigment deposition in lung (maily macrophages)
   2. Simple CWP - coal macules (1-2mm) and larger coal nodules
   3. Progressive Massive Fibrosis (PMF)
2. Usually a benign disease with little effect on lung function
3. Minority of patients develop pulmonary fibrosis
   1. Pulmonary hypertension occurs
   2. This may be followed by Cor Pulmonale
4. Does not predispose to cancers unless patient is also smoking tobacco
5. Initial lesions tend to be in upper lung zones

E. Silicosis [3]

1. Lung disease caused by inhalation of silicone dioxide (silica) or silicates (silicatosis)
2. Currently most common occupational disease in world
3. Slowly progressing, nodules and nodular fibrosis (often asymptomatic)
4. Occupational Risks
   1. Sandblasters
   2. Mine Workers
   3. Stone Cutting
   4. Foundry Work
5. Silica particles stimulate macrophages causing inflammation
6. Talc, vermiculite and mica can cause pneumoconiosis as well
7. May progress to desquamative interstitial pneumonitis (DIP)

F. Asbestos [2]

1. Asbestos is a family of crystalline hydrated silicates which form fibers
2. Associated Diseases
   1. Localized fibrous plaques - most common manifestation of exposure
   2. Diffuse pleural fibrosis - rare
   3. Parenchymal interstitial fibrosis - true asbestosis
   4. Mesothelioma - ~1000X increased risk with asbestos exposure
   5. Bronchogenic Carcinoma - especially in smokers
   6. Papillary Adenocarcinoma of lung [4]
   7. Laryngeal Neoplasms
3. Fibers may adsorb other chemicals (eg. carcinogens) and increase lung deposition
4. Risk Factors
   1. Old Buildings
   2. Shipyards / Naval Yards
5. Pathology [4]
   1. True asbesosis is a pulmonary interstitial fibrotic disease
   2. Asbestos bodies - golden brown rods with translucent fiber and iron-containing material
   3. Macrophages attempting to ingest asbestos particles
   4. Pleural plaques are well circumscribed bundles of dense collagen, often with calcium
   5. The plaques are usually found on parietal pleura and do not contain asbestos bodies
   6. Macrophages may become highly activated and DIP may ensue
6. Clinical Course
   1. Similar to other intersitial lung diseases
   2. Manifestations occur >10-20 years after exposure
   3. Dyspnea is usually first symptoms
   4. Cough with sputum production often present
   5. Progression may occur, with cardiopulmonary failure
   6. Asbestos may initiate mesothelioma or other bronchogenic carcinoma of lung [4]
7. Radiography
   1. Pleural plaques are seen if they are calcified
   2. Irregular parenchymal densities are present
   3. Progressive disease will show honeycombing (especially on CT scan)
8. No known disease-modifying therapy
   1. This is generally true of pneumoconioses
   2. Oxygen should be administered
   3. Lung transplantation may be required

G. Flock Worker's Lung [5]

1. Nylon flocking industry
2. Interstitial Lung Disease
3. Bronchoalveolar (BAL) Findings
   1. About 40% of cases have eosinophilia in BAL fluid
   2. Lymphoid nodules, often with germinal centers
   3. Lymphocytic bronchiolitis
   4. Interstitial fibrosis
4. Nylon fiber is suspected cause of disease

Resources

Aa Gradient

References

1. Beckett WS. 2000. NEJM. 342(6):406
2. Wagner GR. 1997. Lancet. 349:1311
3. Jarvelainen H, Vainionpaa H, Kuopio T, Lehtonen A. 1998. Lancet. 351(9101):494
4. Kradin RL and Mark EJ. 1997. NEJM. 336(26):1895 (Case Record)
5. Kern DG, Crausman RS, durand KTH, et al. 1998. Ann Intern Med. 129(4):261