30 Idiopathic Pulmonary Fibrosis and Other Interstitial Lung Diseases Flashcards

1
Q

Interstitial lung diseases

  • Interstitial lung diseases
    • Affect…
    • Associated with…
    • The process often spills over into…
  • There is a long list of lung insults and injuries that can lead to the development of interstitial lung disease
A
  • Interstitial lung diseases
    • Affect the gas exchange surface of the lung
    • Associated with the accumulation of inflammatory cells, fibroblasts, and fluid in the interstitial space
    • The process often spills over into the alveoli and small airways, but it is the expansion of the interstitial space that is most prominent
  • There is a long list of lung insults and injuries that can lead to the development of interstitial lung disease
    • Infection: viral pneumonia, mycoplasma pneumonia
    • Malignancies: lymphangitic carcinomatosis
    • Sarcoidosis
    • ARDS recovery (almost all will have varying degrees of ILD)
    • Pharmacologic (drug-induced): Amiodarone, Bleomycin, Busulfan, etc.
    • Hypersensitivity pneumonitis: Farmers lung, Pigeon breeders’ lung, etc.
    • Collagen Vascular Diseases: Rheumatoid Arthritis, Scleroderma, DM/PM, SLE, etc.
    • Occupational exposures: Asbestosis, Silicosis, Coal Workers
    • Pneumoconiosis
    • Eosinophilic Granuloma
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2
Q

Interstitial lung diseases

  • Idiopathic interstitial pneumonias (IIP)
  • Members of this class include…
  • Idiopathic pulmonary fibrosis (IPF)
A
  • Idiopathic interstitial pneumonias (IIP)
    • Interstitial lung diseases that have no evident cause
    • A class of lung diseases characterized by the development of variable degrees of inflammation and fibrosis limited to the lung and involving principally the alveolar structures
  • Members of this class include…
    • Acute interstitial pneumonia (AIP)
    • Nonspecific interstitial pneumonia (NSIP)
    • Desquamative interstitial pneumonia/respiratory bronchiolitis with interstitial lung disease (DIP/RBILD)
    • Cryptogenic organizing pneumonia (COP)
      • Formerly called bronchiolitis obliterans with organizing pneumonia
    • Idiopathic pulmonary fibrosis (IPF)
  • Idiopathic pulmonary fibrosis (IPF)
    • One of the more common of the idiopathic interstitial pneumonias
    • Carries the poorest prognosis
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3
Q

Idiopathic pulmonary fibrosis (IPF)

  • General
  • Gender
  • Age
  • Prevalence
  • Geography and race
  • Age-adjusted mortality rates
A
  • General
    • The most common IIP encountered
  • Gender
    • More males have been reported with IPF than females
  • Age
    • ~2/3 of patients with IPF are over the age of sixty at presentation
    • The estimated prevalence of the disease in patients older than 75 years of age is approximately 175 cases per 100,000
  • Prevalence
    • Old data: ~20.2 cases per 100,000 in males and 13.2 cases in females
    • More recent data: incidence in the U.S. is 220/100,000 or ~89,000 cases with 34,000 new cases per year
    • The difference is most likely a consequence of the frequent use of Chest CT scans in the evaluation of patients with lung disease
  • Geography and race
    • No distinct geographical distribution or predilection for race or ethnicity
  • Age-adjusted mortality rates
    • Appear to be higher in whites than blacks, but this may reflect inadequate reporting, healthcare availability or utilization, or, possibly, real differences in disease course
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4
Q

Idiopathic pulmonary fibrosis (IPF)

  • Patients usually present with…
  • Physical examination reveals…
  • The chest radiograph reveals…
A
  • Patients usually present with…
    • Dyspnea on exertion that has been progressing slowly for months or even years
    • Paroxysmal, non-productive cough that is usually provoked by exertion or exposure to irritants
    • A small percentage will have cough productive of mucoid or whitish sputum
      • More common in those who have also smoked
  • Physical examination reveals…
    • Loud (“Velcro”) inspiratory crackles at the lung bases in up to 80% of patients
    • Clubbing of the fingers and toes is seen in 25-50%
  • The chest radiograph reveals…
    • Reticulonodular infiltrates in up to 90% of subjects with a predilection for the lung bases
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5
Q

Idiopathic pulmonary fibrosis (IPF)

  • The high-resolution CT scan
  • Pulmonary function studies reveal…
  • Patients usually experience…
A
  • The high-resolution CT scan
    • The most useful non-invasive test to diagnose idiopathic pulmonary fibrosis
    • Typically demonstrates a sub-pleural distribution of infiltrates which usually consist of honeycombing fibrosis and areas of “traction bronchiectasis”
  • Pulmonary function studies reveal a restrictive impairment.
    • Decreased FVC and FEV1
    • Normal to increased FEV1/FVC
    • Decreased DLco
    • Widened (A-a)PO2 gradient particularly with exertion
  • Patients usually experience…
    • Desaturation of arterial blood with modest exercise when the DLco is less than 50% of predicted
    • Retention of carbon dioxide does not occur until the disease is very advanced
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6
Q

Idiopathic pulmonary fibrosis (IPF):
Natural history

  • Prognosis
  • Survival is adversely affected by the presence of…
  • Even in the absence of complicating disease, the median survival of biopsy-confirmed IPF is…
  • Mortality
A
  • Prognosis
    • Progressive illness
    • Median survival is unaffected by medical therapy
    • Earlier estimates suggesting a longer survival (and better response to therapy) were complicated by the inclusion of other types of IIPs that carry a more favorable prognosis and response to anti-inflammatory and immunosuppressive therapies
  • Survival is adversely affected by the presence of…
    • Concomitant diseases in this elderly population, such as coronary atherosclerotic disease, smoking-related lung disease, chronic obstructive lung disease and bronchogenic carcinoma, and pulmonary infections
  • Even in the absence of complicating disease, the median survival of biopsy-confirmed IPF is…
    • ~3½ years
  • Mortality
    • Most frequently due to respiratory failure from progressive pulmonary fibrosis
    • Ischemic heart disease, bronchogenic carcinoma, infection, and pulmonary emboli accounted for some of the deaths in one series
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7
Q

Idiopathic pulmonary fibrosis (IPF):
Natural history

  • Natural history
  • Some patients experience a gradual decline characterized by…
  • Serial CT scans in such patients generally show…
  • Some patients experience long periods of…
  • A small proportion of patients experience rapid decline in lung function associated with…
  • Lung histology, when available, shows…
A
  • Natural history
    • Highly variable and largely unpredictable
  • Some patients experience a gradual decline characterized by…
    • Worsening dyspnea and diminished exercise capacity as a consequence of progressive interstitial fibrosis and loss of lung function
  • Serial CT scans in such patients generally show…
    • Progressive honeycomb changes extending centrally, with traction bronchiectasis and lung distortion
  • Some patients experience long periods of…
    • Relative stability of lung function, occasionally punctuated by brief periods of accelerated decline
  • A small proportion of patients experience rapid decline in lung function associated with…
    • Severe gas exchange impairment
    • The appearance of ground glass infiltrates on CT scanning
    • Death from respiratory failure within a few weeks to months
  • Lung histology, when available, shows…
    • Diffuse alveolar damage superimposed on the UIP pattern of injury (formerly called Hamman-Rich syndrome), a syndrome now referred to as an acute exacerbation of IPF
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8
Q

Idiopathic pulmonary fibrosis (IPF):
Pathology

  • Hallmarks of usual interstitial pneumonia (UIP)
  • Other findings
  • The most destructive lesions are found…
A
  • Hallmarks of usual interstitial pneumonia (UIP)
    • Geographic and temporal heterogeneity
    • Geographic heterogeneity dictates that there are areas of lung with marked loss of normal architecture such as honeycombing fibrosis adjacent to areas of nearly normal lung
  • Other findings
    • Hyperplasia of smooth muscle within the interstitial space
    • Hyperplasia and metaplasia of epithelial cells in the alveoli and small airways
  • The most destructive lesions are found…
    • In the subpleural and paraseptal areas of the lung
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9
Q

Idiopathic pulmonary fibrosis (IPF):
Pathology

  • Temporal heterogeneity implies that…
  • Inflammation
  • Principal inflammatory cells
A
  • Temporal heterogeneity implies that…
    • Areas of inflammation and advanced scarring are seen in the same specimen
  • Inflammation
    • An early event that progresses to fibrosis
  • Principal inflammatory cells
    • Mononuclear cells, macrophages, lymphocytes, and plasma cells
    • There is a scattering of polymorphonuclear leukocytes, mainly neutrophils, within the interstitium
    • Occasionally, clumps of neutrophils are seen in dilated airways
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10
Q

Idiopathic pulmonary fibrosis (IPF):
Pathology:
Features that characterize the fibrotic response

A
  • The earliest is the “fibroblastic focus” where fibroblasts are undergoing replication
  • These foci usually occur at an air-tissue interface where there is a junction between normal and scarred lung
  • They are felt to be the source of the fibroblasts that lay down immature and mature collagen
  • A large number of fibroblastic foci seem to portend a worse prognosis since they are a marker for the severity of the fibrotic response
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11
Q

Idiopathic pulmonary fibrosis (IPF):
Prognosis

  • Mean survival after diagnosis of IPF vs. non-specific interstitial pneumonitis (NSIP)
  • The traditional concept of how IPF progresses
    • Previous hypothesis
    • Two additional patterns of disease progression
A
  • Mean survival after diagnosis of IPF vs. non-specific interstitial pneumonitis (NSIP)
    • IPF: 3½ years (18% after 6 years, 5% after 17 years)
    • NSIP: much better (75% after 6 years, 50% after 17 years)
    • These differences highlight the importance of making a correct diagnosis
  • The traditional concept of how IPF progresses
    • Previous hypothesis
      • Patients lost lung function is a linear manner over time
      • Eventually they reached the point where they either…
        • Developed terminal respiratory insufficiency with or without infection
        • Died of other causes prior to respiratory failure
    • Two additional patterns of disease progression
      • Patients with well-documented IPF actually may have periods of relative stability interrupted by accelerated declines in lung function over a period of several months
      • Approximately 15% of patients may also experience “acute exacerbations” where the decline in lung function is more precipitous (usually over a period of weeks)
        • These patients are often hospitalized with signs of acute respiratory failure associated with airspace disease on CT scan and (when biopsied) histologic evidence of diffuse alveolar damage
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12
Q

Idiopathic pulmonary fibrosis (IPF):
Pathogenesis

  • Current theories
  • The causes of the initial and recurrent injury
  • The risk of IPF seems higher in…
A
  • Current theories
    • A repetitive injury to the alveolar microenvironment followed by abnormal wound healing
    • Instead of the normal sequence leading to repair and restoration of structure and function, progressive loss of alveoli is due to scarring
  • The causes of the initial and recurrent injury
    • Oxidative stress probably plays a role
  • The risk of IPF seems higher in…
    • Some occupational groups particularly sheet metal workers and workers with heavy sawdust exposure
    • But the majority of subjects with IPF have no occupational exposures
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13
Q

Idiopathic pulmonary fibrosis (IPF):
Pathogenesis

  • Tissue injury is often associated with inflammation
  • Other roles
A
  • Tissue injury is often associated with inflammation
    • Innate immune mechanisms may initiate the response
    • Adaptive immune mechanisms may also be recruited leading to release of immune lymphokines and cytokines
    • Activation of the cellular or humoral immune system in IPF
    • An imbalance between Th1 and Th2 cytokines may contribute to fibrosis.
  • Other roles
    • Angiogenesis
      Growth factor production
    • Fibroblast phenotypes
    • Recruitment and maintenance of the myofibroblast
    • Abnormal turnover of extracellular matrix
    • Loss of epithelial cells may also be due to increased apoptosis of this cell type from mediators that the myofibroblasts release
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14
Q

Idiopathic pulmonary fibrosis (IPF):
Pathogenesis

  • Role of these factors in the IPF lung
  • A familial form of IPF
    • Accounts for…
    • Inheritance
    • Male to female ratio
    • Mutation
A
  • Role of these factors in the IPF lung
    • Upregulation of genes for TGF-β
    • Connective tissue growth factor (CTGF)
    • Matrix metaloproteinases (MMP’s), particularly MMP-7
    • The balance between angiostatic and angiogenic factors
  • A familial form of IPF
    • Accounts for 2-10% of cases
    • An autosomal dominant gene with variable penetrance is the culprit
    • The male to female ratio in familial IPF is about equal
    • Recently a mutation of the gene for Surfactant C was detected in a kindred with…
      • Familial IPF associated with histological UIP
      • Nonspecific Interstitial Pneumonia (NSIP)
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15
Q

Idiopathic pulmonary fibrosis (IPF):
Treatment

  • Proven effective medical therapies for IPF
  • Potentially promising medical therapies
    • High dose corticosteroids
    • Corticosteroids when combined with cyclophosphamide or azathioprine
    • Idiopathic interstitial pneumonias
    • Prednisone, azathioprine, and the antioxidant N-acetylcysteine
    • The short-term efficacy of regimens that combine steroids with colchicine, D-penicillamine, or both
A
  • Proven effective medical therapies for IPF
    • At this time, there are no proven effective medical therapies for IPF
  • Potentially promising medical therapies
    • High dose corticosteroids
      • Decrease mortality
      • Associated with significant and often irreversible side effects
    • Corticosteroids when combined with cyclophosphamide or azathioprine
      • Questionable improved survival compared to corticosteroids alone
    • Idiopathic interstitial pneumonias
      • More steroid-responsive
    • Prednisone, azathioprine, and the antioxidant N-acetylcysteine
      • Increase in mortality
    • The short-term efficacy of regimens that combine steroids with colchicine, D-penicillamine, or both
      • No significant difference in measures of lung function, gas exchange, or survival at the end of 2 years
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16
Q

Idiopathic pulmonary fibrosis (IPF):
Treatment

  • Therapies that target pathways involved in lung fibrosis
    • Pirfenadone
    • Endothelin receptor antagonism, interferon-gamma, etanercept, and sildenafil
    • Nintedanib
  • Lung transplantation
A
  • Therapies that target pathways involved in lung fibrosis
    • Pirfenadone
      • Not approved by the FDA in the U.S., but has gained approval in Japan, India, Europe, and Canada
    • Endothelin receptor antagonism, interferon-gamma, etanercept, and sildenafil
      • Failed to demonstrate efficacy
    • Nintedanib
      • A novel triple-kinase inhibitor
      • Promising results in the US, Europe, and Asia
  • Lung transplantation
    • Currently the only therapeutic option offering long term survival in patients with IPF
    • Given the age of the population affected by this disease, only a limited number can avail themselves of the treatment
17
Q

Occupational lung disease (fibrogenic pneumoconiosis)

  • A complex mix of diseases that occur as a consequence of…
  • The clinical manifestations of occupational lung disease depend on…
  • Dust exposures
  • The term pneumoconiosis is restricted to exclude…
A
  • A complex mix of diseases that occur as a consequence of…
    • Workplace exposure to agents that induce lung disease
  • The clinical manifestations of occupational lung disease depend on…
    • The nature of the offending agent
    • The magnitude of exposure
    • The individual host susceptibility
  • Dust exposures
    • Not all dust exposures lead to the development of pulmonary fibrosis or respiratory impairment
    • The tissue reaction may be fibrogenic or non-fibrogenic
  • The term pneumoconiosis is restricted to exclude…
    • Neoplasms, asthma, bronchitis, and emphysema
    • All of which may be the result of occupational exposure
18
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Silicosis

  • Silicosis
  • Silica
  • Major cause of…
  • At risk occupations
A
  • Silicosis
    • Lung disease that occurs as a consequence of inhalation of silicon dioxide, or silica, in crystalline form (quartz) and, less commonly, cristobalite and tridymite
  • Silica
    • Among the most fibrogenic dusts
    • Often leads to progressive severe disease after exposure
  • Major cause of…
    • Morbidity and mortality in individuals exposed to silica dust in a wide variety of occupations
  • At risk occupations
    • Mining, tunneling, excavating: miners, drillers, tunnelers
    • Quarrying: drillers, hammerer, digger
    • Stonework: cutters, drillers, polishers
    • Foundries: molders, fettlers, casters
    • Abrasives: crushers, pulverizes
    • Ceramics: workers exposed to dry products at any stage
19
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Silicosis:
Clinical features

  • Symptoms of silicosis
  • Simple (chronic) silicosis
  • Complicated silicosis (aka progressive massive fibrosis)
A
  • Symptoms of silicosis
    • Nonspecific, like most of the pneumoconioses
    • Often develop 10 to 20 years after exposure
    • Most common: gradual development of dyspnea
    • Many patients are asymptomatic early in the course of their disease even with an abnormal chest X-ray
  • Simple (chronic) silicosis
    • Diagnosed by the presence of nodules on chest x-ray that are < 1 cm in size
    • Associated with few symptoms or pulmonary function abnormalities
    • Chest X-rays often demonstrate hilar and mediastinal lymph node calcifications
  • Complicated silicosis (aka progressive massive fibrosis)
    • Over time, the nodules may gradually coalesce to form larger nodules (> 1 cm in size)
20
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Silicosis:
Clinical features

  • The transition from simple silicosis to progressive massive fibrosis
  • Acute silicosis
A
  • The transition from simple silicosis to progressive massive fibrosis
    • Highly variable but may occur over a period of 5-20 years
    • When it occurs, the disease is slowly progressive leading to respiratory failure and death
    • In many patients with simple or complicated disease, more rapid progression may be indicative of concurrent mycobacterial infection (either M. tuberculosis or atypical mycobacterial disease)
      • These individuals appear to be more susceptible to mycobacterial disease, because of qualitative or quantitative deficiencies of alveolar macrophage function
  • Acute silicosis
    • An uncommon manifestation of this disease
    • Seen in individuals with massive dust exposure (e.g. sand blasters)
    • They develop an acute airspace disease resembling alveolar proteinosis (airspaces fill with lipoproteinaceous debris)
    • Rapid progression to interstitial fibrosis, respiratory failure, and death
    • Less common now because of strict occupational standards limiting this degree of dust exposure
21
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Silicosis:
Pathology

  • The hallmark lesion of silicosis
  • It is characterized by…
  • Collagen fibers
  • Silicotic islets
A
  • The hallmark lesion of silicosis
    • The silicotic islet or nodule
  • It is characterized by…
    • A cell-free and dust-free central area surrounded by concentrically arranged collagen fibers producing an “onion-like” appearance on cross-section
  • Collagen fibers
    • More loosely arranged in the periphery of the nodule and dust-laden macrophages are often visible
    • Areas of interstitial fibrosis are also seen but are less specific
  • Silicotic islets
    • May appear granulomatous, with multinucleated giant-cells
    • May be seen in the lung parenchyma, lymph nodes, where they may be encased in calcification, or impinging on or eroding into airways
22
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Silicosis:
Radiographic features and pulmonary function testing

  • Uncomplicated (simple) silicosis
  • Complicated silicosis
  • Both simple and complicated silicosis
  • Acute silicosis
  • Restrictive lung disease with a diminution in the diffusing capacity
A
  • Uncomplicated (simple) silicosis
    • Characterized by small (< 1 cm) rounded opacities in the lung, usually with upper lung zone predominance
    • Patients often have normal pulmonary function
  • Complicated silicosis
    • The rounded opacities gradually coalesce to eventually produce large conglomerate masses often in excess of 10-20 centimeters
    • These lesions may form cavities, a finding that often suggests either ischemic necrosis or concurrent infection with mycobacteria
  • Both simple and complicated silicosis
    • Hilar calcifications (so called “eggshell” calcifications because of the cortical distribution within the lymph nodes)
  • Acute silicosis
    • Results from a massive dose of silica exposure
    • Produces a distinct radiographic finding of alveolar filling disease (alveolar proteinosis) which progresses to diffuse pulmonary fibrosis
  • Restrictive lung disease with a diminution in the diffusing capacity
    • The most common pulmonary function abnormality associated with this condition
23
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Asbestosis

  • Asbestos
  • Forms of asbestos
  • What the different forms of asbestos have in common
  • Exposures associated with asbestos-related lung diseases
A
  • Asbestos
    • An ancient mineral that has been exploited over time by humans because of its fibrous nature, heat resistance, and durability
  • Forms of asbestos
    • Crysotile
    • Crocidolite
    • Amosite
  • What the different forms of asbestos have in common
    • A fibrous nature, i.e. they occur in bundles of parallel, radiating, or interlaced fibers that can be easily separated for different manufacturing processes
  • Exposures associated with asbestos-related lung diseases
    • Indirect occupational exposure as a consequence of working in the vicinity of individuals handling asbestos
    • Domestic exposure from handling asbestos-laden work clothes
    • Environmental exposure occurring as a consequence of living near plants containing asbestos
24
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Asbestosis:
Clinical features

  • Asbestosis is a term reserved for individuals who…
  • The disease develops…
  • Radiographically and pathologically the disease is virtually indistinguishable from…
  • Clues to the diagnosis
  • Asbestos bodies
A
  • Asbestosis is a term reserved for individuals who…
    • Develop pulmonary fibrosis as a consequence of asbestos exposure
  • The disease develops…
    • Insidiously with slowly progressive dyspnea and paroxysms of dry cough as the most common symptoms
    • Uncommonly results in death from respiratory failure
  • Radiographically and pathologically the disease is virtually indistinguishable from…
    • Idiopathic pulmonary fibrosis
  • Clues to the diagnosis
    • Careful occupational history
    • The concomitant presence of asbestos related-pleural disease in some but not all patients
  • Asbestos bodies
    • The presence of asbestos bodies (protein coated asbestos fibers) in the lung does not necessarily implicate asbestos as the cause of pulmonary fibrosis
25
Q

Occupational lung disease (fibrogenic pneumoconiosis):
Asbestosis:
Pathology

  • The asbestos body or coated asbestos fiber
  • Asbestos bodies in the sputum
  • Pulmonary fibrosis following asbestos exposure
  • Asbestosis vs. pulmonary fibrosis
A
  • The asbestos body or coated asbestos fiber
    • The hallmark of exposure to asbestos
    • Readily visible by light microscopy
  • Asbestos bodies in the sputum
    • In humans, the number of asbestos bodies in the sputum correlates strongly with the number of fibers in the lung
    • The presence of more than one asbestos body in the sputum is still cited as an important criterion for the diagnosis of asbestosis, although this remains controversial
  • Pulmonary fibrosis following asbestos exposure
    • Typically begins in the subpleural regions
    • Has a lower lobe predominance
  • Asbestosis vs. pulmonary fibrosis
    • There are no specific pathologic features that distinguish asbestosis from other causes of pulmonary fibrosis, except for the presence of asbestos bodies
    • Unlike silicosis (and coal workers pneumoconiosis), the lymph nodes are not usually involved in this disease, and patients do not develop progressive massive fibrosis
26
Q

Coal worker’s pneumoconiosis (CWP):
Pathology

  • Pneumoconiosis secondary to coal dust exposure
  • Simple CWP
    • Diagnosis
    • Pulmonary function tests
    • Symptoms
    • Chest X-ray
  • Complicated CWP (progressive massive fibrosis, PMF)
A
  • Pneumoconiosis secondary to coal dust exposure
    • Has many features similar to silicosis although they are generally less severe
  • Simple CWP
    • Diagnosed because of an abnormal chest X-ray in an individual with coal dust exposure
    • Pulmonary function tests in individuals with simple CWP may be normal or may show a mild restrictive pattern
    • Associated with few symptoms
      • The individuals may have symptoms of cough and sputum production as a consequence of dust-induced chronic bronchitis or concomitant cigarette smoking
    • Chest X-ray demonstrates small rounded opacities less than 1 centimeter in size
  • Complicated CWP (progressive massive fibrosis, PMF)
    • In a small percentage of individuals, the nodules will coalesce to form large masses associated with severe progressive dyspnea and respiratory failure
    • When complicated CWP develops, the nodules coalesce to form large conglomerate masses that migrate centrally and to the upper lung zones
    • Cavitation of these masses sometimes occurs, and the disease process can be accelerated by concomitant mycobacterial disease in a similar fashion to silicosis
27
Q

Coal worker’s pneumoconiosis (CWP):
Pathology

  • Develops as a consequence of…
  • The main occupational risk for this disease
  • The primary lesion in CWP: The coal macule
  • As the lesion enlarges,…
  • As the lesion enlarges with PMF,…
  • The progression from simple to complicated disease
A
  • Develops as a consequence of…
    • The deposition of coal dust in the lungs
  • The main occupational risk for this disease
    • Coal mining
    • Exposure to coal dust continues to be a major contributor to respiratory diseases in this country
  • The primary lesion in CWP: The coal macule
    • A small, pigmented lesion in the lung usually < 4 mm in diameter
    • Formed by an aggregation of dust-laden macrophages and fibroblasts accumulating around respiratory bronchioles
  • As the lesion enlarges,…
    • The bronchial wall weakens and dilates producing an area of focal emphysema
    • Tattooing of the parietal and visceral lymphatics by coal dusts also occur
    • Sometimes subpleural dust deposits and enlarged hilar and mediastinal lymph nodes are present
  • As the lesion enlarges with PMF,…
    • They impinge on blood vessels and obliterate airways, frequently cavitating as a result of ischemic necrosis
  • The progression from simple to complicated disease
    • Occurs less commonly in CWP compared to silicosis
    • Determined by a variety of as yet undefined host factors and/or concomitant mycobacterial disease