Farmer lung - Clinicals, Diagnosis, and Management

Pulmonology

Clinicals - History

Fact Explanation
Shortness of breath This may be acute, subacute or chronic. Acute form is due to a type 3 hypersensitivity reaction, antigens from mouldy hay combines with the antibodies in the lung and is responsible for the initiation of an inflammatory reaction. This causes accumulation of inflammatory cells and release of mediators. Acute form presents with fever, cough, and shortness of breath. Subacute form presents with worsening shortness of breath. Chronic stage is mainly due to the type 4 hypersensitivity reaction and characterised by chronic inflammation with granuloma formation. There will be fibrosis occurring in the lung. Systemic symptoms are more common in chronic stage. Shortness of breath
This may be acute, subacute or chronic. Acute form is due to a type 3 hypersensitivity reaction, antigens from mouldy hay combines with the antibodies in the lung and is responsible for the initiation of an inflammatory reaction. This causes accumulation of inflammatory cells and release of mediators. Acute form presents with fever, cough, and shortness of breath. Subacute form presents with worsening shortness of breath. Chronic stage is mainly due to the type 4 hypersensitivity reaction and characterised by chronic inflammation with granuloma formation. There will be fibrosis occurring in the lung. Systemic symptoms are more common in chronic stage.
Fever, chills Fever is one of the commonest presentations of farmer lung. Exposure to various antigens produces hypersensitivity reactions in the lung with inflammation of the lung parenchyma. Pyrogens released during the inflammation are responsible for the development of fever. Fever, chills
Fever is one of the commonest presentations of farmer lung. Exposure to various antigens produces hypersensitivity reactions in the lung with inflammation of the lung parenchyma. Pyrogens released during the inflammation are responsible for the development of fever.
Non productive cough May be present in both acute or chronic disease. Sometimes this may be the only symptom during chronic phase as they can develop chronic bronchitis. Non productive cough
May be present in both acute or chronic disease. Sometimes this may be the only symptom during chronic phase as they can develop chronic bronchitis.
Chest tightness Hypersensitivity pneumonitis can cause chest tightness and chest pain. Chest tightness
Hypersensitivity pneumonitis can cause chest tightness and chest pain.
Malaise, anorexia and weight loss Patients can present with constitutional problems. Malaise, anorexia and weight loss
Patients can present with constitutional problems.
History of exposure to moldy hay spores The causative factor in the pathogenesis is inhalation of mouldy hay spores which later induces a hypersensitivity reaction in the lung. History of exposure to moldy hay spores
The causative factor in the pathogenesis is inhalation of mouldy hay spores which later induces a hypersensitivity reaction in the lung.
If complicated with respiratory failure This can be associated with severe lung diseases. They may need some kind of respiratory support. If complicated with respiratory failure
This can be associated with severe lung diseases. They may need some kind of respiratory support.

Clinicals - Examination

Fact Explanation
Febrile Patient may present with fever at the acute stage. Febrile
Patient may present with fever at the acute stage.
Tachycardia May be there in acute stage as a compensatory mechanism to impaired gas exchange. Tachycardia
May be there in acute stage as a compensatory mechanism to impaired gas exchange.
Clubbing Patient can develop lung fibrosis and bronchiectasis and chronic lung disease. Clubbing will be a sign at this stage. Clubbing
Patient can develop lung fibrosis and bronchiectasis and chronic lung disease. Clubbing will be a sign at this stage.
Tachypnea and dyspnea May be due to alveolitis, impaired gas exchange and dyspnea may also attributed to malaise. If the exposure to allergen is continued the disease can progress to subacute and chronic stages with worsening of dyspnea. Tachypnea and dyspnea
May be due to alveolitis, impaired gas exchange and dyspnea may also attributed to malaise. If the exposure to allergen is continued the disease can progress to subacute and chronic stages with worsening of dyspnea.
Features of lung fibrosis; Fibrosis may involve bilateral lung bases and they will have reduced chest expansion and movements, dull percussion note, increased vocal resonance and reduced air entry over both lung bases. In a patient who is continuously exposed to allergens the disease can progress to the chronic stage from the acute or subacute stage. Once the disease has progresses to a chronic stage, there will be features of fibrosis. Features of lung fibrosis; Fibrosis may involve bilateral lung bases and they will have reduced chest expansion and movements, dull percussion note, increased vocal resonance and reduced air entry over both lung bases.
In a patient who is continuously exposed to allergens the disease can progress to the chronic stage from the acute or subacute stage. Once the disease has progresses to a chronic stage, there will be features of fibrosis.
Features of hyperinflation; Barrel shape chest, increased resonance on percussion These are signs of chronic disease. Features of hyperinflation; Barrel shape chest, increased resonance on percussion
These are signs of chronic disease.
Inspiratory crackles As the disease progresses there will be fine crackles heard on auscultation over the bi lateral lung bases. Inspiratory crackles
As the disease progresses there will be fine crackles heard on auscultation over the bi lateral lung bases.

Investigations - Diagnosis

Fact Explanation
Leukocytosis Leukocytosis is present in most occasions. There will be marked leukocytosis with neutrophilia and lymphopenia. Leukocytosis
Leukocytosis is present in most occasions. There will be marked leukocytosis with neutrophilia and lymphopenia.
Erythrocyte sedimentation rate (ESR) and C-reactive protein level Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein level Erythrocyte sedimentation rate (ESR) and C-reactive protein level
Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein level
Immunoglobulin level Antibodies to the antigens in mouldy hay is used to detect the disease on certain occasions depend on the clinical features. Precipitating antibodies to thermophilic actinomycetes are usually there. Immunoglobulin level
Antibodies to the antigens in mouldy hay is used to detect the disease on certain occasions depend on the clinical features. Precipitating antibodies to thermophilic actinomycetes are usually there.
Chest x-ray This will show non specific infiltrates. They will also have diffuse air-space consolidation and nodular or reticulonodular pattern. Fibrotic changes will be evident at later stages. Chest x-ray
This will show non specific infiltrates. They will also have diffuse air-space consolidation and nodular or reticulonodular pattern. Fibrotic changes will be evident at later stages.
Bronchoalveolar larvage Shows elevated lymphocytes, neutrophils IgG and IgM due to hypersensitivity reaction. Bronchoalveolar larvage
Shows elevated lymphocytes, neutrophils IgG and IgM due to hypersensitivity reaction.
Lung biopsy This will show granuloma formation and mononuclear cell infiltration. Lung biopsy
This will show granuloma formation and mononuclear cell infiltration.
High-resolution computed tomography There will be fine interstitial fibrosis with a honeycomb appearance of the lung. High-resolution computed tomography
There will be fine interstitial fibrosis with a honeycomb appearance of the lung.

Investigations - Management

Fact Explanation
Lung function test Can be used to monitor the response to therapy. Lung function test
Can be used to monitor the response to therapy.
Pulse oximetry Impaired gas exchange can lead to mild-to-severe hypoxemia. Pulse oximetry
Impaired gas exchange can lead to mild-to-severe hypoxemia.
Diffusion capacity Decreased diffusion capacity is seen as the gas exchange is impaired due to alveolitis. Diffusion capacity
Decreased diffusion capacity is seen as the gas exchange is impaired due to alveolitis.
Lung functions Shows restrictive changes with reduced vital capacity (FVC), total lung capacity (TLC), and forced expiratory volume in first second(FEV1). Lung functions
Shows restrictive changes with reduced vital capacity (FVC), total lung capacity (TLC), and forced expiratory volume in first second(FEV1).
High-resolution computed tomography There will be fine interstitial fibrosis with a honeycomb appearance of the lung. High-resolution computed tomography
There will be fine interstitial fibrosis with a honeycomb appearance of the lung.

Management - Supportive

Fact Explanation
Management of complications If the patient develops complications like respiratory failure, they may need respiratory support with non invasive or invasive ventilation. Management of complications
If the patient develops complications like respiratory failure, they may need respiratory support with non invasive or invasive ventilation.
Symptomatic management Antipyretics, supplemental oxygen may be needed. Symptomatic management
Antipyretics, supplemental oxygen may be needed.
Avoidance of allergens This is the first step in the management, but may not be entirely effective. Education of the farmers about the proper handling may be cost-effective. Avoidance of allergens
This is the first step in the management, but may not be entirely effective. Education of the farmers about the proper handling may be cost-effective.
Pulmonary rehabilitation and exercise Interstitial fibrosis with bronchiectasis will be evident at chronic stage. Reduced lung compliance increases the risk of getting pulmonary infections. Therefore pulmonary rehabilitation plays a vital role in the management. Pulmonary rehabilitation and exercise
Interstitial fibrosis with bronchiectasis will be evident at chronic stage. Reduced lung compliance increases the risk of getting pulmonary infections. Therefore pulmonary rehabilitation plays a vital role in the management.

Management - Specific

Fact Explanation
Steroids Inhaled steroids are used to treat Farmer's lung. Prednisolone 1mg/kg/day is used. Four weeks of treatment is adequate and longer treatment courses have not been proven to be advantageous. Steroids
Inhaled steroids are used to treat Farmer's lung. Prednisolone 1mg/kg/day is used. Four weeks of treatment is adequate and longer treatment courses have not been proven to be advantageous.

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