Mohammad Tohidi M.D.

Professor of Internal Medicine

Department of Pulmonary Medicine

Ghaem Hospital MUMS Mashhad

IRAN

Mohammad Tohidi M.D.

Professor of Internal Medicine

Department of Pulmonary Medicine

Ghaem Hospital MUMS Mashhad

IRAN

SilicosisSilicosis

Case Scenario(1)Case Scenario(1) 57 year old retired non-smoker man 57 year old retired non-smoker man

referred with the cc of dry cough for referred with the cc of dry cough for 1year.In addition he has had mild ED but 1year.In addition he has had mild ED but no other complaint. Past Hx & system no other complaint. Past Hx & system review were negative.His VS,general PE &review were negative.His VS,general PE &

chest exam were normal.Chest X ray chest exam were normal.Chest X ray showed diffuse reticulonodular pattern showed diffuse reticulonodular pattern There were no hilar enlargement & There were no hilar enlargement & calcification.calcification.

Case Scenario(2)Case Scenario(2) HRCT scan of the lung revealed small HRCT scan of the lung revealed small

rounded opacities & thickening of rounded opacities & thickening of alveolar septaalveolar septa

no ground glass pattern,hilar adenopathyno ground glass pattern,hilar adenopathy

& pleural effusion.He had >30 years Hx & pleural effusion.He had >30 years Hx of stone cutting & grinding.With this Hx & of stone cutting & grinding.With this Hx & immaging studies, in the absence of immaging studies, in the absence of another causes,diagnosis of simple another causes,diagnosis of simple silicosis was apparent.silicosis was apparent.

DEFINITIONDEFINITION

Silicosis is a fibrotic lung disease Silicosis is a fibrotic lung disease attributable to the inhalation of attributable to the inhalation of crystalline silica,crystalline silica, usually in the usually in the form of form of quartzquartz and, less and, less commonly, as cristobalite and commonly, as cristobalite and tridymitetridymite

Amorphous silica is relatively Amorphous silica is relatively nontoxicnontoxic

IntroductionIntroduction

SilicosisSilicosis (also known as (also known as Grinder's Grinder's diseasedisease and and Potter's rotPotter's rot) is a form ) is a form of of occupational lung disease caused caused by inhalation of crystalline silica dust, by inhalation of crystalline silica dust, and is marked by and is marked by inflammation and and scarring in forms of nodular lesionsscarring in forms of nodular lesions in in the upper lobes of the the upper lobes of the lungs. .

Where’s it come fromWhere’s it come from??

Crystalline forms of silica Crystalline forms of silica (Silicon (Silicon Dioxide or SiO2)Dioxide or SiO2) include quartz, include quartz, cristobalite, and tridymite. cristobalite, and tridymite. Quartz is the most common type, Quartz is the most common type, and is a major component of and is a major component of rocks including granite, slate, rocks including granite, slate, and sandstone. and sandstone.

SilicaSilica

Silica is the second most Silica is the second most common mineral on earthcommon mineral on earth. . It is found in sand, many It is found in sand, many rocks such as granite, rocks such as granite, sandstone, flint and slate, sandstone, flint and slate, and in some coal and and in some coal and metallic ores. metallic ores.

SilicaSilica The cutting, breaking, The cutting, breaking,

crushing, drilling, grinding, crushing, drilling, grinding, or abrasive blasting of or abrasive blasting of these materials may these materials may produce fine silica dust. produce fine silica dust.

Silicosis – historySilicosis – history This respiratory disease This respiratory disease was first recognized in was first recognized in 1705 by 1705 by Ramazzini who who noticed sand-like noticed sand-like substances in the lungs substances in the lungs of stonecuttersof stonecutters

Silicosis – historySilicosis – history

Full description by Full description by Bernardino Ramazzini Bernardino Ramazzini (1633-1714) in early (1633-1714) in early 1818thth century. century. ““...when ...when the bodies of such the bodies of such workers are workers are dissected, they have dissected, they have been found to be been found to be stuffed with small stuffed with small stones.stones.”” Diseases of Diseases of Workers (De Morbis Workers (De Morbis Artificum Diatriba, Artificum Diatriba, 1713).1713).

Silicosis – historySilicosis – historyThe name silicosis The name silicosis (from the Latin silex (from the Latin silex or flint) was or flint) was attributed to attributed to ViscontiVisconti in 1870 in 1870

Silicosis - historySilicosis - history First U.S. description in 19First U.S. description in 19thth century. century. Term silicosis introduced in 1870, from Latin Term silicosis introduced in 1870, from Latin silexsilex, or flint. , or flint. Prevalence increased markedly with introduction of Prevalence increased markedly with introduction of

mechanized mining.mechanized mining. Came to national attention 1930-1931 with construction of Came to national attention 1930-1931 with construction of

HawkHawk’’s Nest Tunnel in Gauley Bridge, West Virginia. Called s Nest Tunnel in Gauley Bridge, West Virginia. Called ““the worst industrial accident in U.S. history.the worst industrial accident in U.S. history.”” At least 764 At least 764 tunnel workers died from silicosis. Hawktunnel workers died from silicosis. Hawk’’s Nest disaster led to s Nest disaster led to Congressional hearings in 1936, and new laws protecting Congressional hearings in 1936, and new laws protecting workers in many states.workers in many states.

Prevalence of silicosis has greatly declined in recent decades Prevalence of silicosis has greatly declined in recent decades because of effective industrial hygiene measures.because of effective industrial hygiene measures.

Silicosis - historySilicosis - history

The full name for this disease The full name for this disease when caused by the specific when caused by the specific exposure to fine silica dust exposure to fine silica dust found in volcanoes is found in volcanoes is pneumonoultramicroscopicsilicovolcanoconiosis, and at 45 letters it is the , and at 45 letters it is the longest word in any of the major longest word in any of the major English dictionaries. English dictionaries.

Silicosis - historySilicosis - history

The prevalence of silicosis The prevalence of silicosis led some men to grow led some men to grow what is called a what is called a miner's miner's mustachemustache, in an attempt to , in an attempt to intercept as much dust as intercept as much dust as possible. possible.

Diseases Associated with Diseases Associated with Exposure to Silica Dust(1)Exposure to Silica Dust(1)

Silicosis Silicosis Chronic silicosis Chronic silicosis Accelerated silicosis Accelerated silicosis Acute silicosis (silicoproteinosis)(fine dust, Acute silicosis (silicoproteinosis)(fine dust, intense exposure , high silica) intense exposure , high silica)

Progressive massive fibrosis Progressive massive fibrosis Chronic Obstructive Pulmonary Disease Chronic Obstructive Pulmonary Disease

Emphysema Emphysema Chronic bronchitis Chronic bronchitis Mineral dust-induced small airway diseaseMineral dust-induced small airway disease

Diseases Associated with Diseases Associated with Exposure to Silica Dust(2)Exposure to Silica Dust(2)

Lung CancerLung Cancer Mycobacterial InfectionMycobacterial Infection Mycobacterium tuberculosis Mycobacterium tuberculosis Nontuberculous Nontuberculous Mycobacteria Mycobacteria Immune-Related DiseasesImmune-Related Diseases Progressive systemic sclerosis Progressive systemic sclerosis Rheumatoid arthritis Rheumatoid arthritis Chronic renal disease Chronic renal disease Systemic lupus erythematosusSystemic lupus erythematosus

Pulmonary ToxicologyPulmonary Toxicology

•• Particle size is critical.Particle size is critical.•• Peak dust inhalationPeak dust inhalation occurs with particlesoccurs with particles having a diameter of 0.5 tohaving a diameter of 0.5 to 3 microns (μm).3 microns (μm).•• RCS is invisible to theRCS is invisible to the human eye.human eye.•• Pulmonary clearancePulmonary clearance mechanisms:mechanisms: macrophages & themacrophages & the mucociliary escalatormucociliary escalator

The induction period between initial The induction period between initial silica exposure and development of silica exposure and development of radiographically detectable nodular radiographically detectable nodular silicosis is usually silicosis is usually 10 years10 years. Shorter . Shorter induction periods are associated with induction periods are associated with heavy exposures, and acute silicosis heavy exposures, and acute silicosis may develop within may develop within 6 months to 2 6 months to 2 years following massive silica years following massive silica exposureexposure. .

Silicosis is an occupational Silicosis is an occupational hazard to mining, sandblasting, hazard to mining, sandblasting, quarry, ceramics and foundry quarry, ceramics and foundry workers, as well as grinders, workers, as well as grinders, stonecutters and those stonecutters and those continually exposed to silica continually exposed to silica dust. dust.

Variety of occupationsVariety of occupations

Construction, and surface and Construction, and surface and underground rock drilling underground rock drilling

Foundries are also a main source of Foundries are also a main source of silica dust silica dust

workers involved with the repair, workers involved with the repair, rehabilitation, or demolition of rehabilitation, or demolition of concrete structures concrete structures

Variety of occupationsVariety of occupations

New types of pneumoconiosis often New types of pneumoconiosis often turn out to be silicosis in an industry turn out to be silicosis in an industry not previously thought to be at risk not previously thought to be at risk or a or a mixed-dust pneumoconiosismixed-dust pneumoconiosis in in which silica is implicated with other which silica is implicated with other dustsdusts

Silicosis is often the result of Silicosis is often the result of exposure in exposure in the remote pastthe remote past and not and not in the current workplace in the current workplace

Pathology(1)Pathology(1)

When small silica dust particles When small silica dust particles are inhaled, they can embed are inhaled, they can embed themselves deeply into the tiny themselves deeply into the tiny alveolar sacs and ducts in the alveolar sacs and ducts in the lungs, where oxygen and carbon lungs, where oxygen and carbon dioxide gases are exchanged. dioxide gases are exchanged. There, the lungs cannot clear out There, the lungs cannot clear out the dust by mucous or coughing the dust by mucous or coughing

Pathology(2)Pathology(2) Characteristic lung tissue pathology Characteristic lung tissue pathology

in nodular silicosis consists of in nodular silicosis consists of fibrotic nodules with concentric fibrotic nodules with concentric "onion-skinned" arrangement of "onion-skinned" arrangement of collagen fibers, central fibers, central hyalinization, and a cellular hyalinization, and a cellular peripheral zone,peripheral zone, with lightly with lightly birefringent particlesbirefringent particles seen under seen under polarized light polarized light

Pathology(3)Pathology(3) In acute silicosis, microscopic In acute silicosis, microscopic

pathology shows a periodic pathology shows a periodic acid-Schiff positive alveolar acid-Schiff positive alveolar exudate (alveolar exudate (alveolar lipoproteinosis) and a cellular lipoproteinosis) and a cellular infiltrate of the alveolar walls infiltrate of the alveolar walls

SilicosisSilicosis

PATHOGENESIS(1)PATHOGENESIS(1)

1.1. There is agreement that There is agreement that freshly fractured freshly fractured silica,silica, such as that generated during such as that generated during sandblastingsandblasting, is more toxic to the , is more toxic to the alveolar macrophages than is alveolar macrophages than is "aged" "aged" silicasilica

2.2. clay componentsclay components, may adhere to the , may adhere to the surfaces of silica particles, producing surfaces of silica particles, producing "coated" silica"coated" silica, which is less toxic than , which is less toxic than uncoated silica dust uncoated silica dust

3.3. the incidence of silicosis is decreased by the incidence of silicosis is decreased by concomitant exposure to other dustsconcomitant exposure to other dusts

PATHOGENESIS(2)PATHOGENESIS(2)4 The 4 The intensity of the exposureintensity of the exposure

determines the nature of the lung determines the nature of the lung injury. Low-intensity exposure injury. Low-intensity exposure generally produces aggregates of generally produces aggregates of fibrosis with relative sparing of the fibrosis with relative sparing of the lung architecture, whereas lung architecture, whereas high-high-intensity exposure causes widespread intensity exposure causes widespread pulmonary inflammation and collagen pulmonary inflammation and collagen depositiondeposition

5 Individual susceptibility to the 5 Individual susceptibility to the diseasedisease may play a role may play a role

Particles engulfed by macrophages:Particles engulfed by macrophages:

transported upward and removed from lungstransported upward and removed from lungs retained in the lung retained in the lung ““Frustrated PhagocytosisFrustrated Phagocytosis””

cascade of toxic effectscascade of toxic effects

inflammatory process inflammatory process

pneumoconiosispneumoconiosis

fibrosis in the lung tissuefibrosis in the lung tissue

Pathogenesis(3)Pathogenesis(3) When fine particles of silica dust are When fine particles of silica dust are

deposited in the lungs, deposited in the lungs, macrophages that that ingest the dust particles will set off an ingest the dust particles will set off an inflammation response by releasing response by releasing tumor tumor necrosis factorsnecrosis factors, , interleukin-1, , leukotriene B4 and other and other cytokines. In . In turn, these stimulate turn, these stimulate fibroblasts to to proliferate and produce collagen around proliferate and produce collagen around the silica particle, thus resulting in the silica particle, thus resulting in fibrosis and the formation of the nodular lesions and the formation of the nodular lesions

Pathogenesis(4)Pathogenesis(4) Furthermore, the surface of Furthermore, the surface of

silicon dust can generate silicon dust can generate silicon-based radicals that lead silicon-based radicals that lead to the production of to the production of hydroxyl and oxygen radicals, as well as and oxygen radicals, as well as hydrogen peroxide, which can , which can inflict damage to the inflict damage to the surrounding cells surrounding cells

SilicosisSilicosis MC chronic occupational disease in the worldMC chronic occupational disease in the world caused bycaused by inhalation of crystalline silicon dioxide (silica). inhalation of crystalline silicon dioxide (silica). Acute silicosisAcute silicosis - -accumulation of a lipoproteinaceous material within alveoli accumulation of a lipoproteinaceous material within alveoli Chronic silicosisChronic silicosis - slowly progressing, nodular, Fibrosing pneumoconiosis - slowly progressing, nodular, Fibrosing pneumoconiosis PathogenesisPathogenesis crystalline forms -more fibrogenic (crystalline forms -more fibrogenic (quartz quartz ––worstworst)) silica particles silica particles lung macrophages ingest them lung macrophages ingest them activation and release of mediators activation and release of mediators IL-1, TNF,IL-1, TNF,

oxygen-derived free radicalsoxygen-derived free radicals Anti-TNF monoclonal antibodies can block lung collagen accumulation in mice Anti-TNF monoclonal antibodies can block lung collagen accumulation in mice Morphology.Morphology.

• EarlyEarly stages stages ––tiny nodules in the upper zones tiny nodules in the upper zones • disease disease progressesprogresses ––nodules coalesce into nodules coalesce into hard, collagenous scarshard, collagenous scars central softening and central softening and

cavitation (due to superimposed tuberculosis or to ischemia)cavitation (due to superimposed tuberculosis or to ischemia)• X-rayX-ray –– egg shellegg shell calcification in the lymph nodes calcification in the lymph nodes• Advanced stageAdvanced stage - PMF - PMF

HistologyHistology Nodular lesions -concentric layers of hyalinized collagen surrounded by a dense capsuleNodular lesions -concentric layers of hyalinized collagen surrounded by a dense capsule Birefringent silica particles in polarized microscopyBirefringent silica particles in polarized microscopy

EPIDEMIOLOGYEPIDEMIOLOGY

The prevalence of silicosis is difficult to The prevalence of silicosis is difficult to estimate estimate

the reported cases have been estimated to the reported cases have been estimated to represent only represent only one thirdone third of the total cases of the total cases of silicosisof silicosis

In calculating an individual's risk for In calculating an individual's risk for silicosis, silicosis, durationduration and and intensity of intensity of exposureexposure are of primary interest but are of primary interest but peak peak exposureexposure also may be important. also may be important.

EPIDEMIOLOGY(cont’d)EPIDEMIOLOGY(cont’d)

In the United States, NIOSH has In the United States, NIOSH has estimated that at least estimated that at least 1.7 million 1.7 million workersworkers are exposed to silica, of are exposed to silica, of whom between 1500 and 2360 will whom between 1500 and 2360 will develop silicosis each year develop silicosis each year

PrevalencePrevalence

Silicosis is the Silicosis is the most most common occupational lung common occupational lung disease worldwide,disease worldwide, it it occurs everywhere but is occurs everywhere but is especially common in especially common in developing countries developing countries

Silicosis deaths - decliningSilicosis deaths - decliningwww.cdc.gov/mmwr

1,157 (1968) 148 (2002)1,157 (1968) 148 (2002)

CLINICAL FEATURES(1)CLINICAL FEATURES(1)

The main symptom is The main symptom is breathlessnessbreathlessness, first , first noted during exertion and later at rest as noted during exertion and later at rest as the large working reserve of the lung is the large working reserve of the lung is diminished. In chronic silicosis, in the diminished. In chronic silicosis, in the absence of other respiratory disease, even absence of other respiratory disease, even this symptom may be absent this symptom may be absent

a patient with chronic silicosis may a patient with chronic silicosis may present present without symptomswithout symptoms for assessment for assessment of an abnormal chest radiograph of an abnormal chest radiograph

CLINICAL FEATURES(2)CLINICAL FEATURES(2)

The appearance of breathlessness may The appearance of breathlessness may mark the development of a complication mark the development of a complication such as progressive massive fibrosis or such as progressive massive fibrosis or tuberculosis, or may reflect associated tuberculosis, or may reflect associated airway disease airway disease

Cough and sputum productionCough and sputum production are are common symptoms and usually common symptoms and usually relate to chronic bronchitis, but may relate to chronic bronchitis, but may reflect the development of reflect the development of tuberculosis or lung cancer tuberculosis or lung cancer

CLINICAL FEATURES(3)CLINICAL FEATURES(3)

Chest painChest pain is not a feature of is not a feature of silicosis, nor are systemic symptoms silicosis, nor are systemic symptoms such as such as fever and weight lossfever and weight loss, which , which should be attributed to tuberculosis should be attributed to tuberculosis or lung cancer until proven or lung cancer until proven otherwise.otherwise.

ClubbingClubbing is also not a feature of is also not a feature of silicosis silicosis

CLINICAL FEATURES(4)CLINICAL FEATURES(4)

In accelerated and acute silicosis, In accelerated and acute silicosis, the time the time scale of symptom evolutionscale of symptom evolution is is in years or in years or months rather than decadesmonths rather than decades. In acute . In acute silicosis, breathlessness may become silicosis, breathlessness may become disabling within months, followed by disabling within months, followed by

impaired gas exchange impaired gas exchange Cyanosis

Cor pulmonale

Respiratory insufficiencyRespiratory insufficiency

Patients with silicosis are particularly Patients with silicosis are particularly susceptible to tuberculosis (TB) susceptible to tuberculosis (TB) infection - known as infection - known as silicotuberculosis. The reason for the silicotuberculosis. The reason for the increased risk - increased risk - 10-30 fold increased 10-30 fold increased incidenceincidence - is not well understood. It - is not well understood. It is thought that is thought that silica damages silica damages pulmonary macrophages, inhibiting pulmonary macrophages, inhibiting their ability to kill mycobacteriatheir ability to kill mycobacteria

Types of SilicosisTypes of Silicosis

(1) Chronic silicosis(1) Chronic silicosis

Occurs after 15-20 years of exposure to Occurs after 15-20 years of exposure to moderate to low levels of silica dust. moderate to low levels of silica dust. Chronic silicosis itself is further Chronic silicosis itself is further subdivided into: subdivided into:

simple simple

complicated silicosis(PMF)complicated silicosis(PMF)

Chronic silicosisChronic silicosis

This is the most common type This is the most common type of silicosis. Patients with this of silicosis. Patients with this type of silicosis may not have type of silicosis may not have obvious symptoms, so a obvious symptoms, so a chest chest X-ray is necessaryX-ray is necessary to to determine if there is lung determine if there is lung damage. damage.

(2) Asymptomatic silicosis(2) Asymptomatic silicosis Early cases of the disease do Early cases of the disease do

not present any symptomsnot present any symptoms

(3) Accelerated silicosis(3) Accelerated silicosis

Silicosis that develops 5-10 Silicosis that develops 5-10 years after high exposure to years after high exposure to silica dust. Symptoms include silica dust. Symptoms include severe shortness of breath, severe shortness of breath, weakness, and weight lossweakness, and weight loss

(4) Acute silicosis(4) Acute silicosis

Silicosis that develops a Silicosis that develops a few months to 2 years few months to 2 years after exposure to very high after exposure to very high concentrations of silica concentrations of silica dust.dust.

Diagnosis of SilicosisDiagnosis of Silicosis In general, three key elements play a role In general, three key elements play a role

in the diagnosis of silicosis:in the diagnosis of silicosis: A history of silica exposureA history of silica exposure sufficient to sufficient to

cause the degree of illness and the cause the degree of illness and the appropriate latency from the time of first appropriate latency from the time of first exposure exposure

Chest imaging (usually a conventional Chest imaging (usually a conventional chest radiograph) that shows chest radiograph) that shows opacities opacities consistent with silicosis consistent with silicosis

Absence of another diagnosisAbsence of another diagnosis more likely more likely to be responsible for the observed to be responsible for the observed abnormalities abnormalities

Diagnosis of SilicosisDiagnosis of Silicosis Abnormal chest X-ray (or chest CT scan) Abnormal chest X-ray (or chest CT scan)

consistent with silicosisconsistent with silicosis History of History of significantsignificant exposure to silica dust exposure to silica dust Medical evaluation to exclude other possible Medical evaluation to exclude other possible

causes of abnormal chest x-raycauses of abnormal chest x-ray Pulmonary function tests are helpful to Pulmonary function tests are helpful to

gauge severity of impairment, but NOT for gauge severity of impairment, but NOT for diagnosis.diagnosis.

Lung biopsy rarely indicated Lung biopsy rarely indicated (since no (since no effective treatment, biopsy is done only effective treatment, biopsy is done only when other diagnoses are being considered)when other diagnoses are being considered)

Silicosis can be misdiagnosedSilicosis can be misdiagnosed

Silicosis can mimic:Silicosis can mimic:• Sarcoidosis (benign inflammation of unknown Sarcoidosis (benign inflammation of unknown

cause)cause)• Idiopathic pulmonary fibrosis (lung scarring of Idiopathic pulmonary fibrosis (lung scarring of

unknown cause)unknown cause)• Lung cancer Lung cancer • Several other lung conditions (chronic Several other lung conditions (chronic

infection, collagen-vascular disease, etc.)infection, collagen-vascular disease, etc.)

Can usually make right diagnosis with detailed Can usually make right diagnosis with detailed history (occupational & medical) or, rarely, a history (occupational & medical) or, rarely, a lung biopsy.lung biopsy.

LUNG FUNCTIONLUNG FUNCTION

The lung function profile is The lung function profile is determined by the extent of silicosis determined by the extent of silicosis as well as associated or concomitant as well as associated or concomitant airway and vascular changes airway and vascular changes

In chronic silicosis, spirometric tests In chronic silicosis, spirometric tests (FEV1, FEV1/FVC, and maximal (FEV1, FEV1/FVC, and maximal midexpiratory flow) usually reflect midexpiratory flow) usually reflect airflow limitation. airflow limitation.

LUNG FUNCTIONLUNG FUNCTION

In the accelerated and acute forms, In the accelerated and acute forms, functional changes are more marked functional changes are more marked and progression is more rapid. and progression is more rapid. In In acute silicosis, lung function shows a acute silicosis, lung function shows a restrictive defect and impairment of restrictive defect and impairment of gas exchange, which leads to gas exchange, which leads to respiratory failurerespiratory failure and eventually to and eventually to death from intractable hypoxemia death from intractable hypoxemia

LUNG FUNCTIONLUNG FUNCTION

Reduction in diffusing capacityReduction in diffusing capacity is is generally apparent in more advanced generally apparent in more advanced chronic silicosis and probably reflects chronic silicosis and probably reflects associated emphysema. associated emphysema.

It is possible that most of the lung It is possible that most of the lung function changes associated with function changes associated with chronic silicosis can be attributed to chronic silicosis can be attributed to the the associated emphysema. associated emphysema.

Chest imagingChest imaging

The The three main radiographic three main radiographic presentationspresentations of silicosis are: of silicosis are:

simple silicosis simple silicosis progressive massive fibrosisprogressive massive fibrosis

silicoproteinosis silicoproteinosis

Simple silicosisSimple silicosis    

  Simple silicosis refers to a profusion Simple silicosis refers to a profusion of small (less than 10 mm in of small (less than 10 mm in diameter) nodular opacities diameter) nodular opacities (nodules). The nodules are generally (nodules). The nodules are generally rounded but can be irregular, and are rounded but can be irregular, and are distributed predominantly in the distributed predominantly in the upper lung zones upper lung zones

Progressive massive fibrosisProgressive massive fibrosis    

Progressive massive fibrosis (PMF, or Progressive massive fibrosis (PMF, or conglomerate silicosis) occurs when conglomerate silicosis) occurs when these small opacities gradually these small opacities gradually enlarge and coalesce to form larger, enlarge and coalesce to form larger, upper- or mid-zone opacities more upper- or mid-zone opacities more than 10 mm in diameter than 10 mm in diameter

PMFPMF

The hila are retracted upward in The hila are retracted upward in association with upper lobe fibrosis and association with upper lobe fibrosis and lower lobe hyperinflation lower lobe hyperinflation

Hilar adenopathy with prominent Hilar adenopathy with prominent calcification is often present. The opacities calcification is often present. The opacities of PMF can be of PMF can be asymmetricalasymmetrical, and may , and may mimic a neoplastic process. mimic a neoplastic process. Cavitation Cavitation may also be present in advanced disease, may also be present in advanced disease, or in the setting of mycobacterial or in the setting of mycobacterial superinfection superinfection

SilicoproteinosisSilicoproteinosis

Silicoproteinosis occurs following Silicoproteinosis occurs following overwhelming exposure to respirable overwhelming exposure to respirable crystalline silica over a short time, crystalline silica over a short time, and is the radiographic hallmark of and is the radiographic hallmark of acute silicosis The chest radiograph acute silicosis The chest radiograph demonstrates a characteristic basilar demonstrates a characteristic basilar alveolar filling pattern, without alveolar filling pattern, without rounded opacities or lymph node rounded opacities or lymph node calcifications.calcifications.

HRCTHRCT There is general agreement There is general agreement

that CT/HRCT is superior to that CT/HRCT is superior to conventional chest conventional chest radiography for radiography for documentation of PMF lesions documentation of PMF lesions and emphysematous changes and emphysematous changes associated with silicosisassociated with silicosis

pleural effusions are unusual,but pleural effusions are unusual,but pleural thickening appears to be pleural thickening appears to be common, especially among patients common, especially among patients with more severe disease. In a series of with more severe disease. In a series of 110 patients with biopsy proven 110 patients with biopsy proven silicosis followed for a mean of 14 silicosis followed for a mean of 14 years, years, pleural effusions were noted in pleural effusions were noted in 12 patients (11 percent),12 patients (11 percent), but but pleural pleural thickening was present in 64 patients thickening was present in 64 patients (58 percent)(58 percent)

Normal Simple Normal Simple silicosis silicosis

noal

chest

x-ray

Accelerated Silicosis Accelerated Silicosis ( Progressive Massive Fibrosis)( Progressive Massive Fibrosis)

normal chest x-ray normal chest x-ray PMF PMF

Accelerated Silicosis (PMF)Accelerated Silicosis (PMF)

chest x-ray CT scanchest x-ray CT scan

Eggshell calcification – almost Eggshell calcification – almost exclusively silicosisexclusively silicosis

RADIOGRAPHIC FEATURES(2)RADIOGRAPHIC FEATURES(2)

Silicotic nodules are usually, Silicotic nodules are usually, although not invariably, although not invariably, symmetrically distributedsymmetrically distributed and tend to and tend to occur first in the occur first in the upper zonesupper zones .later, .later, although not invariably, other zones although not invariably, other zones are involved. Occasionally the are involved. Occasionally the nodules are nodules are calcifiedcalcified, resembling , resembling microlithiasis microlithiasis

RADIOGRAPHIC FEATURES(3)RADIOGRAPHIC FEATURES(3)

Enlargement of the hilar nodesEnlargement of the hilar nodes may may precede the development of the precede the development of the parenchymal lesionsparenchymal lesions. ". "Eggshell" Eggshell" calcificationcalcification, when present, is , when present, is strongly suggestive although not strongly suggestive although not pathognomonic, of silicosis pathognomonic, of silicosis

Pleural plaquesPleural plaques may occur but are may occur but are not a common feature. not a common feature.

RADIOGRAPHIC FEATURES(4)RADIOGRAPHIC FEATURES(4)

Progressive massive fibrosis is Progressive massive fibrosis is characterized by the characterized by the coalescence of coalescence of small rounded opacities to form small rounded opacities to form larger lesionslarger lesions they are graded on the they are graded on the ILO scale according to size and ILO scale according to size and extent (categories A to C). extent (categories A to C).

RADIOGRAPHIC FEATURES(5)RADIOGRAPHIC FEATURES(5)

CT assessment is superior to the chest CT assessment is superior to the chest radiograph not only in assessing the radiograph not only in assessing the presence and presence and extent of silicotic nodulationextent of silicotic nodulation, , but also in revealing but also in revealing early conglomerationearly conglomeration. .

With time, the mass lesions tend to With time, the mass lesions tend to contract, usually to the upper lobes, leaving contract, usually to the upper lobes, leaving hypertranslucent zoneshypertranslucent zones at their margins at their margins and often at the lung bases. In this process, and often at the lung bases. In this process, small rounded opacities, previously evident, small rounded opacities, previously evident, may may disappeardisappear, resulting in a picture that , resulting in a picture that needs to be distinguished from tuberculosis needs to be distinguished from tuberculosis

RADIOGRAPHIC FEATURES(6)RADIOGRAPHIC FEATURES(6)

The rapid development of The rapid development of several several large lesionslarge lesions suggests suggests rheumatoid rheumatoid silicosissilicosis, but new lesions, especially if , but new lesions, especially if cavitated, should be regarded as cavitated, should be regarded as evidence of mycobacterial disease evidence of mycobacterial disease

Acute silicosis is characterized Acute silicosis is characterized radiologically by diffuse changes that radiologically by diffuse changes that usually display an usually display an air space and air space and interstitial patterninterstitial pattern rather than the rather than the usual nodularity usual nodularity

Diagnosis: SerologyDiagnosis: Serology

HypergammaglobulinemiaHypergammaglobulinemia RFRF ANFANF S-ACES-ACE Increased incidence of systemic Increased incidence of systemic

sclerosissclerosis

described in SA gold miners described in SA gold miners

TreatmentTreatment

Silicosis is an irreversible Silicosis is an irreversible condition with no cure. condition with no cure. Treatment options currently Treatment options currently focus on alleviating the focus on alleviating the symptoms and preventing symptoms and preventing complications complications

TreatmentTreatment The disease will generally The disease will generally

progress even without progress even without further exposure,but the further exposure,but the rate of deterioration is rate of deterioration is probably reduced probably reduced

TreatmentTreatment There is currently interest in There is currently interest in

the use of the use of lung lavagelung lavage to to remove silica from the lung, remove silica from the lung, but a favorable impact on but a favorable impact on progression of acute or progression of acute or chronic silicosis has not been chronic silicosis has not been demonstrateddemonstrated. .

TreatmentTreatment Treatment of all forms of silicosis should Treatment of all forms of silicosis should

be directed toward be directed toward control of control of mycobacterial disease.mycobacterial disease. This is especially This is especially true for acute and accelerated silicosis and true for acute and accelerated silicosis and silicosis in workers with human silicosis in workers with human immunodeficiency virus infection immunodeficiency virus infection

All patients with silicosis should have a All patients with silicosis should have a tuberculin skin test and, if it is positive, be tuberculin skin test and, if it is positive, be offered treatment for latent tuberculosis offered treatment for latent tuberculosis infection infection

TreatmentTreatment Interventions to interrupt the Interventions to interrupt the

inflammatory process that leads to inflammatory process that leads to chronic silicosis including the chronic silicosis including the inhalation of aluminuminhalation of aluminum or or polyvinylpyridine-polyvinylpyridine-NN-oxide-oxide and and oral oral tetrandinetetrandine have have not been shown to not been shown to be successful be successful

TreatmentTreatment The interaction between silica The interaction between silica

exposure and smoking in the exposure and smoking in the development of COPD makes it development of COPD makes it particularly important to implement particularly important to implement smoking cessation programs in the smoking cessation programs in the workplace workplace

TreatmentTreatment Because acute and accelerated Because acute and accelerated

silicosis carry such a poor prognosis silicosis carry such a poor prognosis and tend to occur in younger and tend to occur in younger persons, consideration should be persons, consideration should be given to given to lung transplantationlung transplantation in such in such casescases

PreventionPrevention The best way to prevent The best way to prevent

silicosis is to silicosis is to identify work-identify work-place activitiesplace activities that produce that produce crystalline silica dust and crystalline silica dust and then then to eliminate or controlto eliminate or control the dust. the dust. Water sprayWater spray is often is often used where dust emanates. used where dust emanates. Dust can also be controlled Dust can also be controlled through through dry air filtering dry air filtering

PreventionPrevention The most important aspect of the The most important aspect of the

management of silicosis relates to its management of silicosis relates to its preventionprevention

a sustained effort must be made to a sustained effort must be made to increase awareness of silicosisincrease awareness of silicosis. . Recent deaths from silicosis in Recent deaths from silicosis in younger individuals in the United younger individuals in the United States have occurred after exposure States have occurred after exposure in the in the construction and construction and manufacturing sectorsmanufacturing sectors, with none , with none from mining from mining

SilicosisSilicosis MC chronic occupational disease in the worldMC chronic occupational disease in the world caused bycaused by inhalation of crystalline silicon dioxide (silica). inhalation of crystalline silicon dioxide (silica). Acute silicosisAcute silicosis - -accumulation of a lipoproteinaceous material within accumulation of a lipoproteinaceous material within

alveoli alveoli Chronic silicosisChronic silicosis - slowly progressing, nodular, Fibrosing pneumoconiosis - slowly progressing, nodular, Fibrosing pneumoconiosis PathogenesisPathogenesis crystalline forms -more fibrogenic (crystalline forms -more fibrogenic (quartz quartz ––worstworst)) silica particles silica particles lung macrophages ingest them lung macrophages ingest them activation and activation and

release of mediators release of mediators IL-1, TNF,IL-1, TNF, oxygen-derived free radicals oxygen-derived free radicals Anti-TNF monoclonal antibodies can block lung collagen Anti-TNF monoclonal antibodies can block lung collagen

accumulation in mice accumulation in mice Morphology.Morphology.

• EarlyEarly stages stages ––tiny nodules in the upper zones tiny nodules in the upper zones • disease disease progressesprogresses ––nodules coalesce into nodules coalesce into hard, collagenous scarshard, collagenous scars

central softening and cavitation (due to superimposed tuberculosis or central softening and cavitation (due to superimposed tuberculosis or to ischemia)to ischemia)

• X-rayX-ray –– egg shellegg shell calcification in the lymph nodes calcification in the lymph nodes• Advanced stageAdvanced stage - PMF - PMF

HistologyHistology Nodular lesions -concentric layers of hyalinized collagen surrounded by a Nodular lesions -concentric layers of hyalinized collagen surrounded by a

dense capsuledense capsule Birefringent silica particles in polarized microscopyBirefringent silica particles in polarized microscopy