Pulmonary Hypertension and Pneumonia Quiz
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Questions and Answers

What is the definition of pulmonary hypertension?

  • Mean pulmonary arterial pressure > 20 mmHg (correct)
  • Mean pulmonary arterial pressure < 20 mmHg
  • Elevated blood pressure in both the arteries and veins of the lungs
  • Increased blood flow in the pulmonary arteries

    • Which of these is NOT a common clinical course characteristic of community-acquired bacterial pneumonia?

  • Pleuritic chest pain, often exacerbated by deep breathing.
  • Crackles and rales heard on lung auscultation.
  • Bronchospasm, wheezing, and dyspnea. (correct)
  • Rapid onset of symptoms, often with chills and fever.
  • Productive cough with purulent sputum.

    • What is the primary cause of hemodynamic pulmonary edema?

  • Reduced lymphatic drainage.
  • Alveolar epithelial cell injury.
  • Inflammation and edema in the lung interstitium.
  • Increased capillary hydrostatic pressure. (correct)
  • Increased capillary permeability.

    • Which of the following can cause pulmonary hypertension?

    <p>Both A and B (C)</p> Signup and view all the answers

    Which of the following is NOT considered a pulmonary vascular disease?

    <p>Emphysema. (E)</p> Signup and view all the answers

    What is the most common cause of pulmonary arterial obstructions leading to pulmonary hypertension?

    <p>Thrombotic mechanical obstruction to normal pulmonary blood flow (A)</p> Signup and view all the answers

    What is the primary mechanism by which antigenic drift occurs in Influenza virus type A?

    <p>Mutations in the viral genome, particularly in the genes encoding for hemagglutinin and neuraminidase. (E)</p> Signup and view all the answers

    What is the clinical presentation of pulmonary hypertension?

    <p>Dyspnea, fatigue, syncope, chest pain, and right ventricular hypertrophy (C)</p> Signup and view all the answers

    Which type of pneumonia is most likely to develop in a patient with a weakened immune system after a long hospital stay?

    <p>Hospital-associated pneumonia. (A)</p> Signup and view all the answers

    What is a possible cause of pulmonary hypertension in a patient with systemic sclerosis?

    <p>Pulmonary arterial hypertension (D)</p> Signup and view all the answers

    Which of these factors would likely predisposition patients to pulmonary infections?

    <p>All of the above. (E)</p> Signup and view all the answers

    What are the morphological features of pulmonary hypertension?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the difference between precapillary and postcapillary pulmonary hypertension?

    <p>Precapillary pulmonary hypertension is caused by a problem with the pulmonary arteries, while postcapillary pulmonary hypertension is caused by a problem with the pulmonary veins. (C)</p> Signup and view all the answers

    How does a deficiency of α1-antitrypsin affect lung tissue?

    <p>It increases the risk of developing emphysema. (E)</p> Signup and view all the answers

    What is the most common origin of pulmonary emboli?

    <p>Deep veins of the legs (C)</p> Signup and view all the answers

    Which of the following is a possible cause of undifferentiated or multifactorial pulmonary hypertension?

    <p>Schistosomiasis (C)</p> Signup and view all the answers

    What are the characteristic morphologic changes seen in emphysema?

    <p>Enlargement of air spaces distal to terminal bronchioles with destruction of alveolar walls. (C)</p> Signup and view all the answers

    Which of the following is NOT a common risk factor for pulmonary embolism?

    <p>Hypertension (D)</p> Signup and view all the answers

    What is the clinical significance of a pulmonary embolism dependent upon?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the typical presentation of a pulmonary infarct?

    <p>Initially hemorrhagic, eventually forming a scar (D)</p> Signup and view all the answers

    Which of the following is NOT a symptom of pulmonary embolism?

    <p>Nausea (C)</p> Signup and view all the answers

    What is the primary goal of treatment for pulmonary embolism?

    <p>To prevent further embolism formation (B)</p> Signup and view all the answers

    What is a saddle embolus?

    <p>A large embolus that lodges in the main pulmonary artery or at the bifurcation (C)</p> Signup and view all the answers

    Which of the following is a non-thrombotic pulmonary embolus?

    <p>Both A and C (B)</p> Signup and view all the answers

    What is the term used to describe the structural changes that occur in the airways of individuals with asthma?

    <p>Airway remodeling (B)</p> Signup and view all the answers

    Which of the following is NOT a typical morphological finding in airway remodeling?

    <p>Decreased vascular density (B)</p> Signup and view all the answers

    Which of the following is a characteristic feature of bronchiectasis?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the primary pathological process in idiopathic pulmonary fibrosis?

    <p>Chronic inflammation and fibrosis of the lung parenchyma (C)</p> Signup and view all the answers

    Which of the following is a recognized risk factor for the development of lung cancer?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the most common histological subtype of lung cancer?

    <p>Adenocarcinoma (C)</p> Signup and view all the answers

    Which of the following is a characteristic feature of a functioning carcinoid tumor of the lung?

    <p>Production of hormones (A)</p> Signup and view all the answers

    What is the most common genetic mutation associated with idiopathic pulmonary hypertension?

    <p>Bone morphogenetic protein receptor type 2 (BMPR2) (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic feature of Goodpasture syndrome?

    <p>Presence of anti-neutrophil cytoplasmic antibodies (C)</p> Signup and view all the answers

    What is the most common pattern of metastasis to the lung?

    <p>Hematogenous spread (A)</p> Signup and view all the answers

    What is the typical age range for individuals diagnosed with idiopathic pulmonary hypertension?

    <p>20-40 years old (A)</p> Signup and view all the answers

    Which of the following best describes the mechanism of injury in Goodpasture syndrome?

    <p>Autoimmune attack targeting lung and kidney basement membranes (A)</p> Signup and view all the answers

    What is the main distinguishing characteristic of Granulomatosis and polyangiitis (GPA)?

    <p>Necrotizing vasculitis and parenchymal necrotizing granulomatous inflammation (A)</p> Signup and view all the answers

    What is the significance of hemosiderin-laden macrophages in the lung tissue of individuals with Goodpasture syndrome?

    <p>They are a sign of previous alveolar hemorrhage (A)</p> Signup and view all the answers

    Which of the following is a common symptom of both Granulomatosis and polyangiitis and Goodpasture syndrome?

    <p>Hemoptysis (A)</p> Signup and view all the answers

    Which of the following is a condition that may predispose to pulmonary infection?

    <p>Immunodeficiency (A)</p> Signup and view all the answers

    Which of the following bacteria is most likely to cause pneumonia in an immunocompromised patient due to chemotherapy?

    <p>Pseudomonas aeruginosa (C)</p> Signup and view all the answers

    What is a predisposing condition for aspiration pneumonia?

    <p>Marked debilitation (C)</p> Signup and view all the answers

    What is a hallmark characteristic of aspiration pneumonia?

    <p>Chemical irritation from aspirated gastric contents (D)</p> Signup and view all the answers

    What is a possible outcome of aspiration pneumonia?

    <p>Lung abscess (B)</p> Signup and view all the answers

    Which of the following fungal organisms is commonly associated with pneumonia in immunocompromised patients?

    <p>All of the above (D)</p> Signup and view all the answers

    Flashcards

    Airway remodeling

    Structural changes in the airways due to chronic inflammation, often seen in asthma.

    Asthma triggers

    Environmental and genetic factors that can worsen asthma symptoms and attacks.

    Bronchiectasis

    Chronic condition involving dilation and damage of the bronchial tubes, often linked with infections.

    Fibrosing restrictive lung diseases

    Group of lung diseases characterized by lung tissue scarring and stiffness, affecting breathing.

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    Granulomatous lung diseases

    Diseases characterized by the formation of granulomas, small clusters of immune cells in the lungs.

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    Lung carcinoma types

    Different histological subtypes of lung cancer, each with distinct characteristics and mutations.

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    Carcinoid tumor

    A type of low-grade cancer that can secrete hormones, often found in the lung and digestive tract.

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    Hyperplasia-dysplasia-carcinoma sequence

    Progressive changes in cells from normal to increased growth, to abnormal, leading to cancer.

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    Congenital lung abnormalities

    Abnormal lung development present at birth, affecting function.

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    Atelectasis

    Partial or complete collapse of the lung, preventing gas exchange.

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    Hemodynamic pulmonary edema

    Fluid accumulation due to increased hydrostatic pressure in the lungs.

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    ALI/ARDS

    Acute Lung Injury/Acute Respiratory Distress Syndrome, severe lung inflammation and fluid buildup.

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    Antigenic drift

    Minor changes in the virus over time, affecting immunity.

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    Obstructive lung disease

    Conditions that block airflow, making it hard to breathe out.

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    Chronic bronchitis

    Long-term inflammation of the bronchi, producing mucus and coughing.

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    Atopic asthma

    Asthma triggered by allergens, leading to airway inflammation.

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    Acute Lung Injury

    A condition characterized by diffuse alveolar damage, leading to respiratory failure.

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    Morphology of DAD

    Diffuse alveolar damage shows swollen, heavy lungs with edema and necrotic cells at microscopic level.

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    Pulmonary Embolism (PE)

    A blockage in a pulmonary artery caused by blood clots, leading to significant morbidity and mortality.

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    Risk Factors for PE

    Obesity, surgery, trauma, cancer, immobility, and hormonal factors increase the risk of pulmonary embolism.

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    Saddle Embolus

    A large embolus that blocks the main pulmonary artery or its bifurcation.

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    Pulmonary Infarcts

    Areas of lung tissue death due to lack of blood flow, commonly presenting as hemorrhagic initially.

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    Signs of PE

    Common symptoms include severe chest pain, dyspnea, and in severe cases, shock.

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    Prevention of PE

    Methods include early mobilization, compression stockings, and anticoagulants to reduce clot risk.

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    Aspiration Pneumonia

    Pneumonia caused by inhaling gastric contents into the lungs.

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    Opportunistic Organisms

    Bacteria, viruses, or fungi that infect an immunocompromised host.

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    Mixed Flora in Aspiration

    Presence of both aerobic and anaerobic organisms in aspirated materials.

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    HIV-Related Lung Disease

    Lung infections in HIV patients related to CD4+ T-cell count.

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    Necrotizing Pneumonia

    Severe pneumonia causing lung tissue death, often after aspiration.

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    Idiopathic pulmonary hypertension

    Pulmonary hypertension diagnosed when known causes are excluded, often genetic.

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    BMPR2 mutation

    Inactivating mutation of bone morphogenetic protein receptor type 2 linked to familial pulmonary hypertension.

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    Goodpasture syndrome

    Autoimmune disease causing kidney and lung injury due to antibodies against type IV collagen.

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    Symptoms of Goodpasture syndrome

    Includes hemoptysis, dyspnea, and rapidly progressive glomerulonephritis.

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    Granulomatosis and polyangiitis

    Autoimmune condition with vasculitis and granulomatous inflammation affecting lungs and upper respiratory tract.

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    Anti-neutrophil cytoplasmic antibodies (PR3-ANCAs)

    Antibodies found in over 90% of granulomatosis and polyangiitis cases.

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    Pulmonary infection predispositions

    Conditions like immunodeficiency and chronic diseases that increase risk of lung infections.

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    Defense mechanisms of lungs

    Includes cough reflex, ciliary function, and pulmonary macrophage activity that prevent infections.

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    Pulmonary Hypertension

    Mean pulmonary arterial pressure >20 mmHg.

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    Causes of Pulmonary Hypertension

    Decreased cross-sectional area or increased pulmonary blood flow.

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    Symptoms of Pulmonary Hypertension

    Includes dyspnea, fatigue, syncope, chest pain, and right ventricular hypertrophy.

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    WHO Classification 1

    Pulmonary arterial hypertension due to genetic factors or drugs.

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    WHO Classification 2

    Pulmonary hypertension associated with left heart disease.

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    Chronic Lung Diseases

    Associated with pulmonary hypertension and hypoxia.

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    Pulmonary Vascular Morphology

    Includes medial hypertrophy, sclerosis, and plexiform lesions.

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    Right Ventricular Hypertrophy

    Enlargement of the right ventricle due to increased pressure in pulmonary arteries.

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    Study Notes

    Learning Objectives

    • List and briefly describe common congenital lung abnormalities.
    • Define atelectasis and describe the principal types.
    • Distinguish hemodynamic pulmonary edema from pulmonary edema arising from microvascular injury. Understand and recognize morphologic changes seen with hemodynamic pulmonary edema.
    • Describe acute lung injury/acute respiratory distress syndrome (ALI/ARDS), and understand the associated pathogenesis, morphologic changes, and clinical course.
    • Describe pulmonary vascular diseases, their pathogenesis and courses, including pulmonary embolism, pulmonary hypertension, and pulmonary hemorrhage syndromes.
    • Relate factors predisposing patients to pulmonary infections.
    • List and briefly describe common causative organisms in community-associated bacterial pneumonia.
    • Describe the morphologic changes and clinical course of community-acquired bacterial pneumonia.
    • List common viruses implicated in community-acquired viral pneumonia.
    • Explain the concept of antigenic drift and antigenic shift as observed in influenza virus, type A.
    • Relate the pathogenesis of influenza virus pneumonia, and the morphologic features of viral pneumonia generally.
    • Describe health care-associated pneumonia, hospital-associated pneumonia, aspiration pneumonia, the type of patients typically affected, and the organisms commonly implicated.
    • Describe lung abscess, its pathogenesis, morphologic features, and clinical course.
    • Discuss fungal causes of chronic pneumonia, epidemiologic features, and clinical and pathologic findings.
    • Describe pneumonia in an immunocompromised patient, and list common causative organisms.
    • Briefly discuss pulmonary disease in HIV-infected patients.
    • Define obstructive lung disease and explain common pulmonary function test findings.
    • Describe clinically important subtypes of emphysema, anatomic patterns of involvement, clinical associations, pathogenesis, and morphologic changes seen in emphysema. Explain why emphysema is an obstructive lung disease and relate its clinical course.
    • Describe the effect of a₁-antitrypsin deficiency on lung tissue.
    • Define chronic bronchitis and relate its pathogenesis, morphologic features, and clinical features.
    • Describe asthma and relate the pathogenesis of atopic asthma. Give examples of stimuli known to precipitate asthma.
    • Describe the changes seen in "airway remodeling."
    • Relate genetic and environmental factors known to predispose and precipitate asthma.
    • Describe the morphologic changes and clinical course of asthma.
    • Describe bronchiectasis, and list examples of precipitating causes. Relate the pathogenesis, morphologic features, and clinical course.
    • Describe the general features of chronic diffuse (restrictive) lung diseases.
    • Describe the clinical features, pathogenesis, and morphologic findings of fibrosing restrictive lung diseases, including idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, cryptogenic organizing pneumonia, autoimmune disease-associated lung disease, pneumoconiosis, and therapy-related lung diseases.
    • Describe the morphologic features of usual interstitial pneumonia.
    • Describe the pathogenesis, morphologic findings, and clinical features of granulomatous lung diseases, including sarcoidosis and hypersensitivity pneumonitis.
    • Relate the clinical and morphologic findings in smoking-related interstitial lung diseases, including desquamative interstitial pneumonia and respiratory bronchiolitis-associated interstitial lung disease.
    • Describe the clinical and morphologic features of pulmonary Langerhans cell histiocytosis.
    • Discuss clinicopathologic features of pulmonary alveolar proteinosis and surfactant function disorders.
    • Discuss the epidemiology, etiology, and pathogenesis of lung carcinoma.
    • Describe the clinical and pathological characteristics of major histologic subtypes of lung carcinoma. Identify common mutational abnormalities associated with these subtypes.
    • Understand precursor lesions to lung carcinoma.
    • Describe typical and atypical carcinoid tumor of the lung, and the clinical features of a functioning carcinoid tumor.
    • Describe common patterns of metastases to the lung.
    • Describe malignant mesothelioma, its epidemiologic, clinical, and pathologic features.
    • Describe the morphologic and clinical characteristics of sinonasal and nasopharyngeal tumors, including nasopharyngeal angiofibroma, sinonasal papilloma, olfactory neuroblastoma, and nasopharyngeal carcinoma.
    • Describe benign mass-forming lesions of the larynx, including reactive nodules and squamous papillomas.
    • Describe the clinical characteristics and morphologic features of squamous cell carcinoma of the larynx. Understand the hyperplasia-dysplasia-carcinoma sequence.

    Congenital Anomalies

    • Pulmonary hypoplasia: Decreased weight, volume, and acini for age/body weight; compression of lung(s) in utero (e.g., diaphragmatic hernia); severe cases are fatal shortly after birth.
    • Foregut cyst: Bronchogenic, esophageal, or enteric.
    • Pulmonary sequestration: A segment of lung tissue without airway connection and with systemic circulatory supply (not pulmonary).

    Atelectasis

    • Resorption atelectasis: Complete airway obstruction, air in dependent lung is resorbed, mediastinum shifts toward affected lung.
    • Compression atelectasis: Fluid, tumor, or air accumulate in pleural space, preventing normal expansion—mediastinum shifts away from affected lung.
    • Contraction atelectasis: Pulmonary or pleural fibrosis prevents normal expansion, irreversible.

    Pulmonary Edema

    • Hemodynamic pulmonary edema: Intra-alveolar fluid accumulation due to increased hydrostatic pressure in pulmonary circulation. Fluid accumulation is basally at first, alveolar capillaries are congested, and an intra-alveolar transudate is observed, pink and granular appearance. Hemosiderin-laden macrophages (heart failure cells) may be present with chronic pulmonary edema; the lungs may become edematous, brown, and indurated. Decreased oxygenation and increased infection risk.
    • Microvascular injury pulmonary edema: Injury to or inflammation of alveolar vascular endothelium and/or respiratory epithelium; infectious or toxic insults; can be localized or diffuse.

    Acute Lung Injury/Acute Respiratory Distress Syndrome (ALI/ARDS)

    • Inflammation-induced vascular permeability, leading to diffuse pulmonary edema and rapid onset of hypoxemia.
    • Several predisposing factors, including infectious agents, physical injury, toxic substances, and hemodynamic disturbances.
    • Sepsis, diffuse pulmonary infection, gastric aspiration, and trauma contribute to >50% of cases.
    • Pathogenesis: Endothelial activation, neutrophil accumulation and activation, accumulation of intra-alveolar fluid and hyaline membranes, resolution of injury.
    • Morphology: Grossly heavy, firm, and wet lungs; microvascular changes observed include congested interstitial and intra-alveolar edema, necrosis of type I and type II pneumocytes, presence of hyaline membranes, and collapse of some alveoli—interstitial scarring can also occur.
    • Clinical course depends on cause and severity. Mortality is approximately 40%.

    Pulmonary Embolism

    • Important cause of morbidity and mortality in hospitalized adults.
    • 95% originate in deep veins of the legs.
    • Risk factors: post-surgical (hip/knee), severe trauma/burns, disseminated cancer, congestive heart failure, OCPs/pregnancy, primary hypercoagulable state, immobility.
    • Clinical significance depends on extent of pulmonary artery blood flow obstruction, size of occluded vessel, patient's cardiovascular health, and number of emboli.
    • Consequences: Increase in pulmonary artery pressure from blockage of flow and vasospasm, ischemia of downstream pulmonary parenchyma, sudden death (often due to blockage of blood flow through lungs or acute right-sided heart failure).
    • Usually >60% of pulmonary vasculature obstructed.
    • Saddle embolus: Large embolus lodging in the main pulmonary artery or at the bifurcation.
    • Small emboli travel peripherally, causing infarction and ischemic hemorrhage.
    • Infarcts typically involve lower lobes, and most cases are multiple. Infarcts are initially hemorrhagic (red-blue) and turn to scar tissue.
    • Signs and symptoms: Severe chest pain, dyspnea, and shock; Smaller emboli may be silent and cause transient chest pain and cough. Risk of recurrent PE in patients is approximately 30%.
    • Prevention includes early mobilization, elastic stockings, graduated compression stockings, and anticoagulants; treatment involves anticoagulation and supportive measures.
    • Non-thrombotic emboli: Rare but potentially lethal—air, fat, amniotic fluid and talc common types.

    Pulmonary Hypertension

    • Defined as mean pulmonary arterial pressure >20 mmHg.
    • May be caused by: Decrease of cross-sectional area of pulmonary vascular bed, or increased pulmonary vascular blood flow.
    • Clinically: dyspnea, fatigue, syncope, chest pain, right ventricular hypertrophy, death due to cor pulmonale.
    • WHO Classification:
    • Pulmonary arterial hypertension (PAH): Fibromuscular remodeling of distal pulmonary arterioles - genetic or molecular events, certain toxic drugs (e.g. methamphetamines), liver disease, HIV, or other conditions.
    • Pulmonary hypertension associated with left heart disease
    • Chronic obstructive or interstitial lung diseases and/or hypoxia: Severity is variable.
    • Pulmonary arterial obstructions: Thrombotic mechanical obstruction is common.
    • Undifferentiated or multifactorial causes (e.g., schistosomiasis).
    • Frequently associated with a medial hypertrophy of pulmonary muscular and elastic arteries, pulmonary arterial sclerosis, and plexiform lesions (tufts of capillaries spanning lumens of dilated small arteries).

    Pulmonary Hemorrhage Syndromes

    • Goodpasture syndrome: Kidney and lung injury due to presence of anti-basement membrane antibodies. Usually presents as progressive glomerulonephritis (kidney disease) and necrotizing hemorrhagic interstitial pneumonitis. Common symptoms: hemoptysis, dyspnea. Treatment: plasmapheresis and immunosuppressants.
    • Granulomatosis and polyangiitis (formerly Wegener's granulomatosis): Necrotizing vasculitis; presents with upper respiratory tract (URT) signs and symptoms (e.g. cough, hemoptysis, chest pain, chronic sinusitis, epistaxis, nasal septal perforation), can also involve kidneys, lungs, etc. High correlation (90% of cases) with anti-neutrophil cytoplasmic antibodies (PR3-ANCAs).

    Pulmonary Infections

    • General Considerations: Very common; 8th leading cause of mortality in the US. Underlying systemic conditions (immunodeficiency, chronic diseases, etc.) can predispose to pulmonary infections. Defense mechanisms to pulmonary infections can be compromised (e.g. cough reflex, impaired ciliary function, mucus stasis, decreased pulmonary macrophage activity, pulmonary edema).
    • Community-Acquired Bacterial Pneumonia: Predisposing conditions include: age (young or old), chronic disease (COPD, diabetes, CHF), and absent splenic function (encapsulated bacterial infections). Common causative organisms include Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Legionella pneumophila.
    • Morphology: Consolidation (solidification) of lung tissue results from bacterial invasion, leading to alveolar filling with inflammatory cells & exudate. Patterns: bronchopneumonia (patchy involvement) and lobar pneumonia (entire lobe consolidation). Stages of consolidation include congestion, red hepatization, grey hepatization, and resolution.
    • Clinical course: abrupt fever, shaking chills, productive cough (rust colored sputum), opaque/focal opacities on x-ray. Complications including abscess, empyema (pleural involvement), and bacteremia.
    • Community-Acquired Viral Pneumonia: Common organisms include influenza viruses (A, B, and C), RSV, human metapneumovirus, adenovirus, and rhinoviruses, coronaviruses. Predisposing factors include young age, elderly, malnutrition/alcoholism, and chronic illness. Inflammation & damage to defense systems (ciliary mechanism) lead to bacterial superinfection.
    • Influenza virus: Causes epidemics and pandemics. The viral proteins hemagglutinin and neuraminidase facilitate infection and viral release, respectively. Frequent antigenic drift and shift (genome rearrangement) lead to new viral strains and pandemics. Infection generally involves the upper respiratory tract, and then the infection spreads to the lungs via respiratory epithelium leading to intraalveolar fluid accumulation, cell death, and inflammation. Prominent lung findings: patchy or extensive vascular congestion, inflammation in the interstitial tissue, and edema
    • Clinical course depends on host immune status, virulence, and co-occurring conditions.
    • COVID-19: Transmission by respiratory droplets. Potential for abnormally increased cytokine response, development of arterial and venous thrombosis. A wide range of clinical presentations, from asymptomatic to severe pulmonary disease and multiorgan failure, depending on host factors.
    • Chronic Pneumonia: Infectious agents include endemic fungi in the US (histoplasmosis and blastomycosis) and inhaled soil particles contaminated by bird/bat droppings. Histoplasmosis: Typically a self-limiting infection; possible progression to extensive pulmonary infection (extra pulmonary involvement). Blastomycosis: Typically presents with productive cough, chest pain, headache, anorexia, and fever. Coccidiomycosis: Involves inhalation of airborne arthroscones leading to lung granulomas—involves cell-mediated immunity.
    • Hospital-acquired pneumonia: This occurs typically following a hospital stay. Predisposing conditions include mechanical ventilation, severe underlying disease, immunosuppression, and invasive access devices. Common causative organisms are gram-positive cocci (e.g., S. aureus) and gram-negative rods (e.g., Enterobacteriaceae, Pseudomonas spp.).
    • Aspiration pneumonia: Occurs when gastric contents are aspirated into lungs. Predisposing factors include debilitation, unconsciousness, or conditions affecting swallowing (stroke). Usually mixed flora is involved, with a high likelihood of chemical irritation causing a potential for necrotizing pneumonia and lung abscess development.
    • Pneumonia in an immunocompromised host: May result from any cause of immunosuppression. Organisms are highly opportunistic, including bacteria (Pseudomonas aeruginosa, Mycobacterium spp.), viruses (cytomegalovirus [CMV], herpesviruses), and fungi (Pneumocystis jirovecii, Candida spp., Aspergillus spp., Cryptococcus neoformans, Mucormycoses), and can cause pulmonary infiltrates that may need differentiation from other causes.
    • HIV-related lung disease: Contributes to 30-40% of hospitalizations of HIV+ patients. Opportunistic infections often depend on CD4+ T-cell count; a count of >200 cells/mL favors bacterial/tubercular infections vs <200/mL favors Pneumocystis pneumonia. Common accompanying infections include Kaposi sarcoma, non-Hodgkin lymphoma, and lung cancer.
    • Lung abscess: Defined as local suppurative process producing lung tissue necrosis. Arises from material aspiration. Antecedent primary lung infections are common causes. Complications include septic embolism caused by infective endocarditis, and the possibility of neoplastic obstruction leading to infection.

    Tuberculosis (TB)

    • Causative organism: Mycobacterium tuberculosis. Infection via airborne droplets—entry into macrophages, replication within macrophages, seeding of multiple sites, bacteremia. Immune response: Cell-mediated (immune cells attempt to contain infection, three weeks post exposure). Granulomatous inflammation/tissue damage.
    • Primary TB: Infection in a previously unexposed patient; development of a "Ghon complex" (focal lung parenchyma consolidation/necrosis, hilar lymph node(s) with caseating necrosis); a focus of pulmonary scarring results. Approximately 5% develop significant disease at this point, often in immunocompromised patients.
    • Secondary TB: Arises from dormant primary lesions in a previously sensitized host, often occurring in apices of one or both lungs; widespread systemic dissemination possible. Often involves multiple lesions. Common sites of disseminated involvement include liver, bone marrow, spleen, adrenal glands - disseminated TB may present in single organ (vertebrae: Pott's disease).

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